Who first developed attachment theory in psychology?

Attachment-based therapy applies to interventions or approaches based on attachment theory, originated by John Bowlby. These range from individual therapeutic approaches to public health programs to interventions specifically designed for foster carers. Although attachment theory has become a major scientific theory of socioemotional development with one of the broadest, deepest research lines in modern psychology, attachment theory has, until recently, been less clinically applied than theories with far less empirical support. This may be partly due to lack of attention paid to clinical application by Bowlby himself and partly due to broader meanings of the word 'attachment' used amongst practitioners. It may also be partly due to the mistaken association of attachment theory with the pseudo-scientific interventions misleadingly known as attachment therapy. The approaches set out below are examples of recent clinical applications of attachment theory by mainstream attachment theorists and clinicians and are aimed at infants or children who have developed or are at risk of developing less desirable, insecure attachment styles or an attachment disorder.

Attachment-based therapy (children)

This intervention was developed from "infant–parent psychotherapy", a psychoanalytic approach to treating disturbed infant–parent relationships based on the theory that disturbances are manifestations of unresolved conflicts in the parent's past relationships. The "patient" is the infant–parent relationship. Infant–parent psychotherapy was expanded by Alicia Lieberman and colleagues into child–parent psychotherapy, a manualized intervention for impoverished and traumatised families with children under the age of 5. In addition to the focus on the parents early relationships the intervention also addresses current life stresses and cultural values. CPP is supported by five randomized trials showing efficacy in increasing attachment security, maternal empathy and goal-corrected partnerships. The trials also showed a reduction in avoidance, resistance and anger. The therapy is delivered through unstructured weekly sessions involving both parent/s and child over the course of a year. The trials were conducted with low income groups, maltreating families, families with depressed mothers and families where children were exposed to domestic violence.

This is a parent education and psychotherapy intervention developed by Glen Cooper, Kent Hoffman, Robert Marvin, and Bert Powell designed to shift problematic or 'at risk' patterns of attachment – caregiving interactions to a more appropriate developmental pathway. It is stated that it is explicitly based on contemporary attachment and congruent developmental theories. Its core constructs are Ainsworth’s ideas of a Secure Base and a Haven of Safety (Ainsworth et al. 1978). The aim of the protocol is to present these ideas to the parents in a user-friendly, common-sense fashion that they can understand both cognitively and emotionally. This is done by a graphic representation of the child's needs and attachment system in circle form, summarising the child's needs and the safe haven provided by the caregiver. The protocol has so far been aimed at and tested on preschoolers up to the age of 4 years.

The aim of the therapy is:

Its four core principles are: that the quality of the child parent attachment plays a significant role in the life trajectory of the child; that lasting change results from parents changing their caregiving patterns rather than by learning techniques to manage their child's behaviors; that parents relationship capacities are best enhanced if they themselves are operating within a secure base relationship; and that interventions designed to enhance the quality of child–parent attachments will be especially effective if they are focused on the caregiver and based on the strengths and difficulties of each caregiver/child dyad.

There is an initial assessment which utilises the 'Strange Situation' procedure, (Ainsworth 1978), observations, a videotaped interview using the Parent Development Interview (Aber et al. 1989) and the Adult Attachment Interview (George et al. 1984) and caregiver questionnaires regarding the child. The child's attachment pattern is classified using either Ainsworth or the PAC (Preschool Attachment Classification System). The therapy is then 'individualized' according to each dyads attachment/caregiver pattern. The programme, which takes place weekly over 20 weeks, consists of group sessions, video feedback vignettes and psycho-educational and therapeutic discussions. Caregivers learn, understand and then practice observational and inferential skills regarding their children's attachment behaviors and their own caregiving responses.

Circle of Security is being field tested within the 'Head Start'/'Early Head Start' programme in the USA. According to the developers the goal of the project is to develop a theory- and evidence-based intervention protocol that can be used in a partnership between professionals trained in scientifically based attachment procedures, and appropriately trained community-based practitioners. It is reported that preliminary results of data analysis of 75 dyads suggest a significant shift from disordered to ordered patterns, and increases in classifications of secure attachment. The process of validation is not yet completed.

This was an attempt to collect and synthesise the data to try to come to "evidence-based" conclusions on the best intervention practices for attachment in infants. There were four hypotheses:

The selection criteria were very broad, intending to include as many intervention studies as possible. Sensitivity findings were based on 81 studies involving 7,636 families. Attachment security involved 29 studies and 1,503 participants. Assessment measures used were the Ainsworth sensitivity rating, Ainsworth et al. (1974), the Home Observation for Measurement of the Environment, Caldwell and Bradley (1984), the Nursing Child Assessment Teaching Scale, Barnard et al. (1998) the Erickson rating scale for maternal sensitivity and supportiveness, Egeland et al. (1990).

The conclusion was that "Interventions with an exclusively behavioural focus on maternal sensitivity appear to be most effective not only in enhancing maternal sensitivity but also in promoting children's attachment security." p212.

Three studies were singled out by Prior and Glaser to illustrate intervention processes which have shown good results. p239-244.

This intervention involved mothers and infants referred for a community health service. Presenting problems included feeding, sleeping, behavioural regulation, maternal depression and feelings of failure in bonding or attachment. The randomly assigned control group undertook psychodynamic psychotherapy.

The primary work is between mother and therapist. It is based on the notion of the infant as initiator in infant–parent psychotherapy. For half the session the mother gets down on the floor with the infant, observes it and interacts only on the infant's initiative. The idea is that it increases the mother's sensitivity and responsiveness by fostering an observational reflective stance, whilst also being physically accessible. Also the infant has the experience of negotiating their relationship with their mother. For the second half the mother discusses her observations and experiences.

Infants in the watch, wait and wonder group were significantly more likely to shift to a secure or organised attachment classification than infants in the psychodynamic psychotherapy group although there was no differential treatment effect in maternal sensitivity. It has been pointed out however that specific caregiver responses to attachment (the precursors to secure attachments) were not measured.

This intervention focused on low socio-economic group mothers with irritable infants, assessed on a behavioural scale. The randomly assigned group received 3 treatment sessions, between the ages of 6 and 9 months, based on maternal responsiveness to negative and positive infant cues. Intervention was based on Ainsworth's sensitive responsiveness components, namely perceiving a signal, interpreting it correctly, selecting an appropriate response and implementing the response effectively.

It was found that these infants scored significantly higher than the control infants on sociability, self soothing and reduced crying. All maternal components improved. Further, a'strange situation' assessment carried out at 12 months showed only 38% classified as insecure compared to 78% in the control group.

Follow ups at 18, 24 and 42 months using Ainsworth's Maternal Sensitivity Scales, the Bayley Scales of Infant Development, the Child Behaviour Checklist (Achenbach) and the Attachment Q-sort showed enduring significant effects in secure attachment classification, maternal sensitivity, fewer behaviour problems, and positive peer relationships.

This intervention aimed to reduce inappropriate caregiver behaviours as measured on the AMBIANCE (atypical maternal behaviour instrument for assessment and classification). Such inappropriate behaviours are thought to contribute to disorganized attachment. The play focused intervention (MIG) was compared with a behaviour modification intervention focused on feeding. A significant decrease in inappropriate maternal behaviours and disrupted communication was found in the MIG group.

Developed and evaluated by Juffer, Bakermans-Kranenburg and Van IJzendoorn, this collection of interventions aim to promote maternal sensitivity through the review of taped infant–parent interactions and written materials. The programme can also be expanded to include the parents internal working models (VIPP-R) and/or sensitive disciplinary practices (VIPP-SD). Findings from randomized controlled trials are mixed but overall supportive of efficacy, particularly for "highly reactive infants" and in reducing later externalising behaviours. The various versions show promise but research continues.

Developed by Daniel Schechter and colleagues. They developed an experimental paradigm informed by attachment theory called the Clinician Assisted Videofeedback Exposure Sessions to test whether traumatized mothers, who often suffered psychological sequalae from a history of abuse and violence, could "change their mind" about their young children. The technique used was to watch video-excerpts of play, separation and similarly stressful moments in the presence of a clinician who asks the mother to think about what she (and her child) might be thinking and feeling at the time of the excerpt and at the moment of videofeedback. It applies the principles of mentalization as an aide to emotional regulation with these traumatized parents. It also involves elements of prolonged exposure treatment, the video-based treatment Interaction Guidance, and psychodynamically-oriented child–parent psychotherapy. Schechter and colleagues showed a significant change in the way mothers perceived their own child and their relationship together.

In video interaction guidance the client is guided to analyse and reflect on video clips of their own interactions (e.g. a mother with her infant). Research results include that VIG enhances positive parenting skills, decreases/alleviates parental stress and is related to more positive development of the children. VIG is recommended by NICE in the UK.

This is a scheme in which a version of the Circle of Security intervention was added to a jail diversion program for pregnant women with a history of substance abuse. Preliminary data indicates a 68% rate of secure infant–mother attachment in the first relatively small (19) sample. This is a rate of secure attachment typically found in low risk samples.

This project tested the provision of 25 sessions of child–parent psychotherapy (see above) for mothers investigated or substantiated for child maltreatment through court-based teams. There were no further reports of maltreatment by participants during and immediately after the programme and positive changes in maternal and child behaviours were noted. The advocacy organisation Zero to Three is supporting such teams being established in other states.

This an intervention programme aimed at infants who have experienced early adverse care and disruptions in care. It aims to provide specialized help for foster carers in recognition of the fact that a young child placed in foster care has to deal with the loss of attachment figures at a time when maintaining contact with attachment figures is vital. It targets key issues: providing nurturance for infants when the carers are not comfortable providing nurturance, overriding tendencies to respond in kind to infant behaviors and providing a predictable interpersonal environment.

It is essentially a training programme for surrogate caregivers. It has four main components based on four propositions:

Caregiver and child behaviors are assessed before and after intervention, as is the child's regulation of neuroendocrine function. The intervention consists of 10 sessions administered in caregivers homes by professional social workers. Sessions are videotaped for feedback and for fidelity. The intervention is currently being assessed in a randomized clinical trial involving 200 foster families, supported by the National Institute of Mental Health. Half the infants are assigned to the Developmental Education for Families programme as a comparison intervention. (DEF:Dozier 2003). The developers themselves point out that they do not test for caregiver commitment although they state this may or may not be a critical omission as they consider caregiver commitment to be a crucial variable in terms of child outcomes.

A modified version has been introduced for birth parents which is currently being tested in a small group.

This is a foster care intervention devised by J.A. Larrieu and C.H Zeanah in 1998. The program is designed to address the developmental and health needs of children under the age of 5 who have been maltreated and placed in foster care. It is funded by the state government of Louisiana and private funds. It is a multidisciplinary approach involving psychiatrists, psychologists, social workers, paediatricians and paraprofessionals—all with expertise in child development and developmental psychopathology.

The aim of the intervention is to support the building of an attachment relationship between the child and foster carers, even though about half of the children eventually return to their parents after about 12 to 18 months. The designers note Mary Doziers program to foster the development of relationships between children and foster carers (ABC) and her work showing the connection between foster children's symptomology and foster carers attachment status. Work is based on findings that the qualitative features of a foster parents narrative descriptions of the child and relationship with the child have been strongly associated with the foster parents behavior with the child and the child's behavior with them. The aim was to develop a programme for designing foster care as an intervention.

The theoretical base is attachment theory. There is a conscious effort to build on recent, although limited, research into the incidence and causes of reactive attachment disorder and risk factors for RAD and other psychopathologies.

Soon after coming into care the children are intensively assessed, in foster care, and then receive multi modal treatments. Foster carers are also formally assessed using a structured clinical interview which includes in particular the meaning of the child to the foster parent. Individualised interventions for each child are devised based on age, clinical presentation and information on the child/foster carer match. The assessment 'team' remains involved in delivering the intervention. Those running the programme maintain regular phone and visit contact and there are support groups for foster parents.

Barriers to attachment are considered to be as follows;

Interventions include supporting foster parents to learn to help the child in regulating emotions, to learn to respond effectively to the child's distress and to understand the child's signals, especially'miscues' as the signals of such children are often confusing as a consequence of their often frightening, inconsistent and confusing past relationships. Foster carers are taught to recognize what such children actually need rather than what they may appear to signal that they need. Such children often exhibit provocative and oppositional behaviors which may normally trigger feelings of rejection in caregivers. Withdrawn children may be overlooked and seemingly independent, indiscriminate children may be considered to be managing much better than they are. Foster carers are regularly contacted and visited to assess their needs and progress.

, 250 children had participated in the programme. Outcome data published in 2001 revealed a 68% reduction in maltreatment recidivism for the same child returning to its parent(s)and a 75% reduction in recidivism for a subsequent child of the same mother. The authors claim the programme not only assists the building of new attachments to foster parents but also has the potential impact a families development long after a returned child is no longer in care.

It is critical to differentiate therapies based on attachment theory from the "unfortunately named" attachment therapy. (However, the use of the terms "attachment therapy" and "attachment-based therapy" is not consistent in literature and on the Internet). Attachment therapy, also known as 'holding therapy', is a group of unvalidated therapies characterized by forced restraint of children in order to make them relive attachment-related anxieties; a practice considered incompatible with attachment theory and its emphasis on'secure base'. The conceptual focus of these treatments is the child's individual internal pathology and past caregivers rather than current parent-child relationships or current environment. This form of therapy, including diagnosis and accompanying parenting techniques, is scientifically unvalidated and is not considered to be part of mainstream psychology or, despite its name, to be based on attachment theory, with which it is considered incompatible. In 2006, the American Professional Society on the Abuse of Children (APSAC) Task Force reported on the subjects of attachment therapy, reactive attachment disorder, and attachment problems and laid down guidelines for the future diagnosis and treatment of attachment disorders. The Taskforce was largely critical of attachment therapy's theoretical base, practices, claims to an evidence base, non-specific symptoms lists published on the internet, claims that traditional treatments do not work and dire predictions for the future of children who do not receive attachment therapy. The controversy also extends to the theories, diagnoses, diagnostic practices, beliefs, and social group norms and patient recruitment and advertising practices.

Attachment theory, originally developed by John Bowlby, focuses on the importance of open, intimate, emotionally meaningful relationships. Attachment is described as a biological system or powerful survival impulse that evolved to ensure the survival of the infant. A child who is threatened or stressed will move toward caregivers who create a sense of physical, emotional and psychological safety for the individual. Attachment feeds on body contact and familiarity. Later Mary Ainsworth developed the Strange Situation protocol and the concept of the secure base.

Developmental psychology

Developmental psychology is the scientific study of how and why human beings change over the course of their life. Originally concerned with infants and children, the field has expanded to include adolescence, adult development, aging, and the entire lifespan. Developmental psychologists aim to explain how thinking, feeling, and behaviors change throughout life. This field examines change across three major dimensions: physical development, cognitive development, and socioemotional development. Within these three dimensions are a broad range of topics including motor skills, executive functions, moral understanding, language acquisition, social change, personality, emotional development, self-concept, and identity formation.

Developmental psychology examines the influences of nature "and" nurture on the process of human development, and processes of change in context and across time. Many researchers are interested in the interactions among personal characteristics, the individual's behavior, and environmental factors, including the social context and the built environment. Ongoing debates include biological essentialism vs. neuroplasticity and stages of development vs. dynamic systems of development.

Developmental psychology involves a range of fields, such as educational psychology, child psychopathology, forensic developmental psychology, child development, cognitive psychology, ecological psychology, and cultural psychology. Influential developmental psychologists from the 20th century include Urie Bronfenbrenner, Erik Erikson, Sigmund Freud, Jean Piaget, Barbara Rogoff, Esther Thelen, and Lev Vygotsky.

John B. Watson and Jean-Jacques Rousseau are typically cited as providing the foundations for modern developmental psychology. In the mid-18th century Jean Jacques Rousseau described three stages of development: "infants" (infancy), "puer" (childhood) and "adolescence" in "". Rousseau's ideas were taken up strongly by educators at the time.

It generally focuses on how and why certain modifications throughout an individual’s life-cycle (cognitive, social, intellectual, personality) and human growth change over time. There are many theorists that have made a profound contribution to this area of psychology. For example, Erik Erikson developed a model of eight stages of psychological development. He believed that humans developed in stages throughout their lifetimes and this would affect their behaviors (Similar ideas to Sigmund Freud)

In the late 19th century, psychologists familiar with the evolutionary theory of Darwin began seeking an evolutionary description of psychological development; prominent here was the pioneering psychologist G. Stanley Hall, who attempted to correlate ages of childhood with previous ages of humanity. James Mark Baldwin who wrote essays on topics that included "Imitation: A Chapter in the Natural History of Consciousness" and "Mental Development in the Child and the Race: Methods and Processes". James Mark Baldwin was heavily involved in the theory of developmental psychology. Sigmund Freud, whose concepts were developmental, significantly affected public perceptions.

Sigmund Freud believed that we all had a conscious, preconscious, and unconscious level. In the conscious, we are aware of our mental process. The preconscious involves information that, though not currently in our thoughts, can be brought into consciousness. Lastly, the unconscious includes mental processes we are unaware of.

He believed there is tension between the conscious and unconscious because the conscious tries to hold back what the unconscious tries to express. To explain this he developed three personality structures: the id, ego, and superego. The id, the most primitive of the three, functions according to the pleasure principle: seek pleasure and avoid pain. The superego plays the critical and moralizing role; and the ego is the organized, realistic part that mediates between the desires of the id and the superego.

Based on this, he proposed five universal stages of development, that each is characterized by the erogenous zone that is the source of the child's psychosexual energy. The first is the "oral stage", which occurs from birth to 12 months of age. During the oral stage, "the libido is centered in a baby's mouth." The baby is able to suck. The second is the "anal stage", from one to three years of age. During the anal stage, the child defecates from the anus and is often fascinated with their defecation. The third is the "phallic stage", which occurs from three to five years of age (most of a person's personality forms by this age). During the phallic stage, the child is aware of their sexual organs. The fourth is the "latency stage", which occurs from age five until puberty. During the latency stage, the child's sexual interests are repressed. Stage five is the "genital stage", which takes place from puberty until adulthood. During the genital stage, puberty starts happening.

Jean Piaget, a Swiss theorist, posited that children learn by actively constructing knowledge through hands-on experience. He suggested that the adult's role in helping the child learn was to provide appropriate materials that the child can interact with and use to construct. He used Socratic questioning to get children to reflect on what they were doing, and he tried to get them to see contradictions in their explanations.

Piaget believed that intellectual development takes place through a series of stages, which he described in his theory on cognitive development. Each stage consists of steps the child must master before moving to the next step. He believed that these stages are not separate from one another, but rather that each stage builds on the previous one in a continuous learning process. He proposed four stages: "sensorimotor", "pre-operational", "concrete operational", and "formal operational". Though he did not believe these stages occurred at any given age, many studies have determined when these cognitive abilities should take place.

Piaget claimed that logic and morality develop through constructive stages. Expanding on Piaget's work, Lawrence Kohlberg determined that the process of moral development was principally concerned with justice, and that it continued throughout the individual's lifetime.

He suggested three levels of moral reasoning; pre-conventional moral reasoning, conventional moral reasoning, and post-conventional moral reasoning. The pre-conventional moral reasoning is typical of children and is characterized by reasoning that is based on rewards and punishments associated with different courses of action. Conventional moral reason occurs during late childhood and early adolescence and is characterized by reasoning based on rules and conventions of society. Lastly, post-conventional moral reasoning is a stage during which the individual sees society's rules and conventions as relative and subjective, rather than as authoritative.

Kohlberg used the Heinz Dilemma to apply to his stages of moral development. The Heinz Dilemma involves Heinz's wife dying from cancer and Heinz having the dilemma to save his wife by stealing a drug. Preconventional morality, conventional morality, and post-conventional morality applies to Heinz's situation.

German-American psychologist Erik Erikson and his collaborator and wife, Joan Erikson, conceptualized eight stages of psychosocial development that they theorized healthy individuals pass through as they develop from infancy to adulthood. The first stage is called "Trust vs. Mistrust" takes place in infancy. The best virtue for the first stage is hope, in the infant learning who to trust and having hope for a supportive group of people to be there for him/her. The second stage is "Autonomy vs. Shame and Doubt" with the best virtue being will. This takes place in early childhood where the child learns to become more independent by discovering what they are capable of where if the child is overly controlled, they believe to feel inadequate on surviving by themselves, which can lead to low self-esteem and doubt. The third stage is "Initiative vs. Guilt". The basic virtue that would be gained is the purpose and takes place in the play age. This is the stage where the child will be curious and have many interactions with other kids. They will ask many questions as their curiosity grows. If too much guilt is present, the child may have a slower and harder time interacting with other children. The fourth stage is "Industry (competence) vs. Inferiority". The basic virtue for this stage is competency which happens at the school age. This stage is when the child will try to win the approval of others and fit in and understand the value of their accomplishments. The fifth stage is "Identity vs. Role Confusion". The basic virtue gained is fidelity which takes place in adolescence. This is where the child will start to find who he/she is as a person in society. What sex role he/she picks. The sixth stage is "Intimacy vs. Isolation", which happens in young adults and the virtue gained is love. This is where the person will start to share his/her life with someone else intimately and emotionally. In not doing so, it could lead to isolation. The seventh stage is "Generativity vs. Stagnation". This happens in adulthood and the virtue gained would be care. We become stable and start to give back by raising a family and becoming involved in the community. The eighth stage is "Ego Integrity vs. Despair". This happens during maturity and wisdom is gained. When one grows old and they contemplate and look back and see the success or failure of their life. This is also the stage where one can also have closure and accept death without fearing anything.

Michael Commons enhanced and simplified Bärbel Inhelder and Piaget's developmental theory and offers a standard method of examining the universal pattern of development. The Model of Hierarchical Complexity (MHC) is not based on the assessment of domain-specific information, It divides the Order of Hierarchical Complexity of tasks to be addressed from the Stage performance on those tasks. A stage is the order hierarchical complexity of the tasks the participant's successfully addresses. He expanded Piaget's original eight stage (counting the half stages) to fifteen stages. The stages are : 0 Calculatory; 1 Sensory & Motor; 2 Circular sensory-motor; 3 Sensory-motor; 4 Nominal; 5 Sentential; 6 Preoperational; 7 Primary; 8 Concrete; 9 Abstract; 10 Formal; 11 Systematic; 12 Metasystematic; 13 Paradigmatic; 14 Cross-paradigmatic; 15 Meta-Cross-paradigmatic. The order of hierarchical complexity of tasks predicts how difficult the performance is with an R ranging from 0.9 to 0.98.

In the MHC, there are three main axioms for an order to meet in order for the higher order task to coordinate the next lower order task. Axioms are rules that are followed to determine how the MHC orders actions to form a hierarchy. These axioms are: a) defined in terms of tasks at the next lower order of hierarchical complexity task action; b) defined as the higher order task action that organizes two or more less complex actions; that is, the more complex action specifies the way in which the less complex actions combine; c) defined as the lower order task actions have to be carried out non-arbitrarily.

Ecological systems theory, originally formulated by Urie Bronfenbrenner, specifies four types of nested environmental systems, with bi-directional influences within and between the systems. The four systems are microsystem, mesosystem, exosystem, and macrosystem. Each system contains roles, norms and rules that can powerfully shape development. The microsystem is the direct environment in our lives such as our home and school. Mesosystem is how relationships connect to the microsystem. Exosystem is a larger social system where the child plays no role. Macrosystem refers to the cultural values, customs and laws of society.

The microsystem is the immediate environment surrounding and influencing the individual (example: school or the home setting). The mesosystem is the combination of two microsystems and how they influence each other (example: sibling relationships at home vs. peer relationships at school). The exosystem is the interaction among two or more settings that are indirectly linked (example: a father's job requiring more overtime ends up influencing his daughter's performance in school because he can no longer help with her homework). The macrosystem is broader taking into account social economic status, culture, beliefs, customs and morals (example: a child from a wealthier family sees a peer from a less wealthy family as inferior for that reason). Lastly, the chronosystem refers to the chronological nature of life events and how they interact and change the individual and their circumstances through transition (example: a mother losing her own mother to illness and no longer having that support in her life).

Since its publication in 1979, Bronfenbrenner's major statement of this theory, "The Ecology of Human Development" has had widespread influence on the way psychologists and others approach the study of human beings and their environments. As a result of this conceptualization of development, these environments—from the family to economic and political structures—have come to be viewed as part of the life course from childhood through to adulthood.

Lev Vygotsky was a Russian theorist from the Soviet era, who posited that children learn through hands-on experience and social interactions with members of his/her culture. Unlike Piaget, he claimed that timely and sensitive intervention by adults when a child is on the edge of learning a new task (called the "zone of proximal development") could help children learn new tasks. This adult role is often referred to as the skilled "master," whereas the child is considered the learning apprentice through an educational process often termed "cognitive apprenticeship" Martin Hill stated that "The world of reality does not apply to the mind of a child." This technique is called "scaffolding," because it builds upon knowledge children already have with new knowledge that adults can help the child learn. Vygotsky was strongly focused on the role of culture in determining the child's pattern of development, arguing that development moves from the social level to the individual level. In other words, Vygotsky claimed that psychology should focus on the progress of human consciousness through the relationship of an individual and their environment. He felt that if scholars continued to disregard this connection, then this disregard would inhibit the full comprehension of the human consciousness.

Constructivism is a paradigm in psychology that characterizes learning as a process of actively constructing knowledge. Individuals create meaning for themselves or make sense of new information by selecting, organizing, and integrating information with other knowledge, often in the context of social interactions. Constructivism can occur in two ways: individual and social. Individual constructivism is when a person constructs knowledge through cognitive processes of their own experiences rather than by memorizing facts provided by others. Social constructivism is when individuals construct knowledge through an interaction between the knowledge they bring to a situation and social or cultural exchanges within that content.

Jean Piaget, a Swiss developmental psychologist, proposed that learning is an active process because children learn through experience and make mistakes and solve problems. Piaget proposed that learning should be whole by helping students understand that meaning is constructed.

Evolutionary developmental psychology is a research paradigm that applies the basic principles of Darwinian evolution, particularly natural selection, to understand the development of human behavior and cognition. It involves the study of both the genetic and environmental mechanisms that underlie the development of social and cognitive competencies, as well as the epigenetic (gene-environment interactions) processes that adapt these competencies to local conditions.

EDP considers both the reliably developing, species-typical features of ontogeny (developmental adaptations), as well as individual differences in behavior, from an evolutionary perspective. While evolutionary views tend to regard most individual differences as the result of either random genetic noise (evolutionary byproducts) and/or idiosyncrasies (for example, peer groups, education, neighborhoods, and chance encounters) rather than products of natural selection, EDP asserts that natural selection can favor the emergence of individual differences via "adaptive developmental plasticity." From this perspective, human development follows alternative life-history strategies in response to environmental variability, rather than following one species-typical pattern of development.

EDP is closely linked to the theoretical framework of evolutionary psychology (EP), but is also distinct from EP in several domains, including research emphasis (EDP focuses on adaptations of ontogeny, as opposed to adaptations of adulthood) and consideration of proximate ontogenetic and environmental factors (i.e., how development happens) in addition to more ultimate factors (i.e., why development happens), which are the focus of mainstream evolutionary psychology.

Attachment theory, originally developed by John Bowlby, focuses on the importance of open, intimate, emotionally meaningful relationships. Attachment is described as a biological system or powerful survival impulse that evolved to ensure the survival of the infant. A child who is threatened or stressed will move toward caregivers who create a sense of physical, emotional and psychological safety for the individual. Attachment feeds on body contact and familiarity. Later Mary Ainsworth developed the Strange Situation protocol and the concept of the secure base.

Theorists have proposed four types of attachment styles: secure, anxious-avoidant, anxious-resistant, and disorganized. Secure attachment is a healthy attachment between the infant and the caregiver. It is characterized by trust. Anxious-avoidant is an insecure attachment between an infant and a caregiver. This is characterized by the infant's indifference toward the caregiver. Anxious-resistant is an insecure attachment between the infant and the caregiver characterized by distress from the infant when separated and anger when reunited. Disorganized is an attachment style without a consistent pattern of responses upon return of the parent.

A child can be hindered in its natural tendency to form attachments. Some babies are raised without the stimulation and attention of a regular caregiver or locked away under conditions of abuse or extreme neglect. The possible short-term effects of this deprivation are anger, despair, detachment, and temporary delay in intellectual development. Long-term effects include increased aggression, clinging behavior, detachment, psychosomatic disorders, and an increased risk of depression as an adult.

Attachment style can affect the relationships between people. Attachment is established in early childhood and attachment continues into adulthood. An example of secure attachment continuing in adulthood would be when the person feels confident and is able to meet their own needs. An example of anxious attachment during adulthood is when the adult chooses a partner with anxious-avoidant attachment.

A significant issue in developmental psychology is the relationship between innateness and environmental influence in regard to any particular aspect of development. This is often referred to as "nature and nurture" or nativism versus empiricism. A nativist account of development would argue that the processes in question are innate, that is, they are specified by the organism's genes.

An empiricist perspective would argue that those processes are acquired in interaction with the environment. Today developmental psychologists rarely take such polarised positions with regard to most aspects of development; rather they investigate, among many other things, the relationship between innate and environmental influences. One of the ways this relationship has been explored in recent years is through the emerging field of evolutionary developmental psychology.

One area where this innateness debate has been prominently portrayed is in research on language acquisition. A major question in this area is whether or not certain properties of human language are specified genetically or can be acquired through learning. The empiricist position on the issue of language acquisition suggests that the language input provides the necessary information required for learning the structure of language and that infants acquire language through a process of statistical learning. From this perspective, language can be acquired via general learning methods that also apply to other aspects of development, such as perceptual learning.

The nativist position argues that the input from language is too impoverished for infants and children to acquire the structure of language. Linguist Noam Chomsky asserts that, evidenced by the lack of sufficient information in the language input, there is a universal grammar that applies to all human languages and is pre-specified. This has led to the idea that there is a special cognitive module suited for learning language, often called the language acquisition device. Chomsky's critique of the behaviorist model of language acquisition is regarded by many as a key turning point in the decline in the prominence of the theory of behaviorism generally. But Skinner's conception of "Verbal Behavior" has not died, perhaps in part because it has generated successful practical applications.

Since theorists believe that development is a smooth, continuous process, individuals gradually add more of the same types of skills throughout their lives. Other theorists, however, think that development takes place in discontinuous stages. People change rapidly and step up to a new level, and then change very little for a while. With each new step, the person shows interest and responds to the world qualitatively.

This issue involves the degree to which we become older renditions of our early experience or whether we develop into something different from who we were at an earlier point in development. It considers the extent to which early experiences ( especially infancy) or later experiences are the key determinants of a person's development.

Most lifespan developmentalists, recognise that extreme positions are unwise. Therefore, the key to a comprehensive understanding of development at any stage requires the ·interaction of different factors and not only one.

Developmental psychology is concerned not only with describing the characteristics of psychological change over time but also seeks to explain the principles and internal workings underlying these changes. Psychologists have attempted to better understand these factors by using models. A model must simply account for the means by which a process takes place. This is sometimes done in reference to changes in the brain that may correspond to changes in behavior over the course of the development.

Mathematical modeling is useful in developmental psychology for implementing theory in a precise and easy-to-study manner, allowing generation, explanation, integration, and prediction of diverse phenomena. Several modeling techniques are applied to development: symbolic, connectionist (neural network), or dynamical systems models.

Dynamic systems models illustrate how many different features of a complex system may interact to yield emergent behaviors and abilities. Nonlinear dynamics has been applied to human systems specifically to address issues that require attention to temporality such as life transitions, human development, and behavioral or emotional change over time. Nonlinear dynamic systems is currently being explored as a way to explain discrete phenomena of human development such as affect, life transitions, second language acquisition, and locomotion.

Cognitive development is primarily concerned with the ways that infants and children acquire, develop, and use internal mental capabilities such as: problem-solving, memory, and language. Major topics in cognitive development are the study of language acquisition and the development of perceptual and motor skills. Piaget was one of the influential early psychologists to study the development of cognitive abilities. His theory suggests that development proceeds through a set of stages from infancy to adulthood and that there is an end point or goal.

Other accounts, such as that of Lev Vygotsky, have suggested that development does not progress through stages, but rather that the developmental process that begins at birth and continues until death is too complex for such structure and finality. Rather, from this viewpoint, developmental processes proceed more continuously. Thus, development should be analyzed, instead of treated as a product to obtain.

K. Warner Schaie has expanded the study of cognitive development into adulthood. Rather than being stable from adolescence, Schaie sees adults as progressing in the application of their cognitive abilities.

Modern cognitive development has integrated the considerations of cognitive psychology and the psychology of individual differences into the interpretation and modeling of development. Specifically, the neo-Piagetian theories of cognitive development showed that the successive levels or stages of cognitive development are associated with increasing processing efficiency and working memory capacity. These increases explain differences between stages, progression to higher stages, and individual differences of children who are the same-age and of the same grade-level. However, other theories have moved away from Piagetian stage theories, and are influenced by accounts of domain-specific information processing, which posit that development is guided by innate evolutionarily-specified and content-specific information processing mechanisms.

Developmental psychologists who are interested in social development examine how individuals develop social and emotional competencies. For example, they study how children form friendships, how they understand and deal with emotions, and how identity develops. Research in this area may involve study of the relationship between cognition or cognitive development and social behavior.

Emotional regulation or ER refers to an individual's ability to modulate emotional responses across a variety of contexts. In young children, this modulation is in part controlled externally, by parents and other authority figures. As children develop, they take on more and more responsibility for their internal state. Studies have shown that the development of ER is affected by the emotional regulation children observe in parents and caretakers, the emotional climate in the home, and the reaction of parents and caretakers to the child's emotions.

Music also has an influence on stimulating and enhancing the senses of a child through self-expression.

A child's social and emotional development can be disrupted by motor coordination problems as evidenced by the environmental stress hypothesis. The environmental hypothesis explains how children with coordination problems and developmental coordination disorder are exposed to several psychosocial consequences which act as secondary stressors, leading to an increase in internalizing symptoms such as depression and anxiety. Motor coordination problems affect fine and gross motor movement as well as perceptual-motor skills. Secondary stressors commonly identified include the tendency for children with poor motor skills to be less likely to participate in organized play with other children and more likely to feel socially isolated.

Social and emotional development focuses on 5 keys areas: Self-Awareness, Self Management, Social Awareness, Relationship Skills and Responsible Decision Making.

Physical development concerns the physical maturation of an individual's body until it reaches the adult stature. Although physical growth is a highly regular process, all children differ tremendously in the timing of their growth spurts. Studies are being done to analyze how the differences in these timings affect and are related to other variables of developmental psychology such as information processing speed. Traditional measures of physical maturity using x-rays are less in practice nowadays, compared to simple measurements of body parts such as height, weight, head circumference, and arm span.

A few other studies and practices with physical developmental psychology are the phonological abilities of mature 5- to 11-year-olds, and the controversial hypotheses of left-handers being maturationally delayed compared to right-handers. A study by Eaton, Chipperfield, Ritchot, and Kostiuk in 1996 found in three different samples that there was no difference between right- and left-handers.

Researchers interested in memory development look at the way our memory develops from childhood and onward. According to Fuzzy-trace theory, we have two separate memory processes: verbatim and gist. These two traces begin to develop at different times as well as at a different pace. Children as young as 4 years-old have verbatim memory, memory for surface information, which increases up to early adulthood, at which point it begins to decline. On the other hand, our capacity for gist memory, memory for semantic information, increases up to early adulthood, at which point it is consistent through old age. Furthermore, our reliance on gist memory traces increases as we age.

Developmental psychology employs many of the research methods used in other areas of psychology. However, infants and children cannot be tested in the same ways as adults, so different methods are often used to study their development.

Developmental psychologists have a number of methods to study changes in individuals over time. Common research methods include systematic observation, including naturalistic observation or structured observation; self-reports, which could be clinical interviews or structured interviews; clinical or case study method; and ethnography or participant observation. These methods differ in the extent of control researchers impose on study conditions, and how they construct ideas about which variables to study. Every developmental investigation can be characterized in terms of whether its underlying strategy involves the "experimental", "correlational", or "case study" approach. The experimental method involves "actual manipulation of various treatments, circumstances, or events to which the participant or subject is exposed; the "experimental design" points to cause-and-effect relationships. This method allows for strong inferences to be made of causal relationships between the manipulation of one or more independent variables and subsequent behavior, as measured by the dependent variable. The advantage of using this research method is that it permits determination of cause-and-effect relationships among variables. On the other hand, the limitation is that data obtained in an artificial environment may lack generalizability. The correlational method explores the relationship between two or more events by gathering information about these variables without researcher intervention. The advantage of using a correlational design is that it estimates the strength and direction of relationships among variables in the natural environment; however, the limitation is that it does not permit determination of cause-and-effect relationships among variables. The case study approach allows investigations to obtain an in-depth understanding of an individual participant by collecting data based on interviews, structured questionnaires, observations, and test scores. Each of these methods have its strengths and weaknesses but the experimental method when appropriate is the preferred method of developmental scientists because it provides a controlled situation and conclusions to be drawn about cause-and-effect relationships.

Most developmental studies, regardless of whether they employ the experimental, correlational, or case study method, can also be constructed using research designs. Research designs are logical frameworks used to make key comparisons within research studies such as:

In a longitudinal study, a researcher observes many individuals born at or around the same time (a cohort) and carries out new observations as members of the cohort age. This method can be used to draw conclusions about which types of development are universal (or normative) and occur in most members of a cohort. As an example a longitudinal study of early literacy development examined in detail the early literacy experiences of one child in each of 30 families.

Researchers may also observe ways that development varies between individuals, and hypothesize about the causes of variation in their data. Longitudinal studies often require large amounts of time and funding, making them unfeasible in some situations. Also, because members of a cohort all experience historical events unique to their generation, apparently normative developmental trends may, in fact, be universal only to their cohort.

In a cross-sectional study, a researcher observes differences between individuals of different ages at the same time. This generally requires fewer resources than the longitudinal method, and because the individuals come from different cohorts, shared historical events are not so much of a confounding factor. By the same token, however, cross-sectional research may not be the most effective way to study differences between participants, as these differences may result not from their different ages but from their exposure to "different" historical events.

A third study design, the sequential design, combines both methodologies. Here, a researcher observes members of different birth cohorts at the same time, and then tracks all participants over time, charting changes in the groups. While much more resource-intensive, the format aids in a clearer distinction between what changes can be attributed to an individual or historical environment from those that are truly universal.

Because every method has some weaknesses, developmental psychologists rarely rely on one study or even one method to reach conclusions by finding consistent evidence from as many converging sources as possible.

Prenatal development is of interest to psychologists investigating the context of early psychological development. The whole prenatal development involves three main stages: germinal stage, embryonic stage and fetal stage. Germinal stage begins at conception until 2 weeks; embryonic stage means the development from 2 weeks to 8 weeks; fetal stage represents 9 weeks until birth of the baby. The senses develop in the womb itself: a fetus can both see and hear by the second trimester (13 to 24 weeks of age). The sense of touch develops in the embryonic stage (5 to 8 weeks). Most of the brain's billions of neurons also are developed by the second trimester. Babies are hence born with some odor, taste and sound preferences, largely related to the mother's environment.

Some primitive reflexes too arise before birth and are still present in newborns. One hypothesis is that these reflexes are vestigial and have limited use in early human life. Piaget's theory of cognitive development suggested that some early reflexes are building blocks for infant sensorimotor development. For example, the tonic neck reflex may help development by bringing objects into the infant's field of view.

Other reflexes, such as the walking reflex appear to be replaced by more sophisticated voluntary control later in infancy. This may be because the infant gains too much weight after birth to be strong enough to use the reflex, or because the reflex and subsequent development are functionally different. It has also been suggested that some reflexes (for example the moro and walking reflexes) are predominantly adaptations to life in the womb with little connection to early infant development. Primitive reflexes reappear in adults under certain conditions, such as neurological conditions like dementia or traumatic lesions.

Ultrasound has shown that infants are capable of a range of movements in the womb, many of which appear to be more than simple reflexes. By the time they are born, infants can recognize and have a preference for their mother's voice suggesting some prenatal development of auditory perception. Prenatal development and birth complications may also be connected to neurodevelopmental disorders, for example in schizophrenia. With the advent of cognitive neuroscience, embryology and the neuroscience of prenatal development is of increasing interest to developmental psychology research.

Several environmental agents—teratogens—can cause damage during the prenatal period. These include prescription and nonprescription drugs, illegal drugs, tobacco, alcohol, environmental pollutants, infectious disease agents such as the rubella virus and the toxoplasmosis parasite, maternal malnutrition, maternal emotional stress, and Rh factor blood incompatibility between mother and child. There are many statistics which prove the effects of the aforementioned substances. A leading example of this would be that, in America alone, approximately 100,000-375,000 'cocaine babies' are born on an annual basis. This is a result of an expectant mother abusing the drug while pregnant. 'Cocaine babies' are proven to have quite severe and lasting difficulties which persist throughout infancy and right throughout childhood. The drug also encourages behavioural problems in the affected children, as well as defects of various vital organs.

From birth until the first year, the child is referred to as an infant. Developmental psychologists vary widely in their assessment of infant psychology, and the influence the outside world has upon it, but certain aspects are relatively clear.

The majority of a newborn infant's time is spent in sleep. At first, this sleep is evenly spread throughout the day and night, but after a couple of months, infants generally become diurnal.

Infants can be seen to have six states, grouped into pairs:

Infant perception is what a newborn can see, hear, smell, taste, and touch. These five features are better known as one's "five senses". Infants respond to stimuli differently in these different states.Babies are born with the ability to discriminate virtually all sounds of all human languages. Infants of around six months can differentiate between phonemes in their own language, but not between similar phonemes in another language. At this stage infants also start to babble, producing phonemes.

Piaget suggested that an infant's perception and understanding of the world depended on their motor development, which was required for the infant to link visual, tactile and motor representations of objects. According to this view, it is through touching and handling objects that infants develop object permanence, the understanding that objects are solid, permanent, and continue to exist when out of sight.
Piaget's sensorimotor stage comprised six sub-stages (see sensorimotor stages for more detail). In the early stages, development arises out of movements caused by primitive reflexes. Discovery of new behaviors results from classical and operant conditioning, and the formation of habits. From eight months the infant is able to uncover a hidden object but will persevere when the object is moved.

Piaget came to his conclusion that infants lacked a complete understanding of object permanence before 18 months after observing infants' failure before this age to look for an object where it was last seen. Instead, infants continue to look for an object where it was first seen, committing the "A-not-B error." Some researchers have suggested that before the age of eight to nine months, infants' inability to understand object permanence extends to people, which explains why infants at this age do not cry when their mothers are gone ("Out of sight, out of mind").

In the 1980s and 1990s, researchers have developed many new methods of assessing infants' understanding of the world with far more precision and subtlety than Piaget was able to do in his time. Since then, many studies based on these methods suggest that young infants understand far more about the world than first thought.

Based on recent findings, some researchers (such as Elizabeth Spelke and Renee Baillargeon) have proposed that an understanding of object permanence is not learned at all, but rather comprises part of the innate cognitive capacities of our species.

Other research has suggested that young infants in their first six months of life may possess an understanding of numerous aspects of the world around them, including:There are critical periods in infancy and childhood during which development of certain perceptual, sensorimotor, social and language systems depends crucially on environmental stimulation. Feral children such as Genie, deprived of adequate stimulation, fail to acquire important skills and are unable to learn in later childhood. The concept of critical periods is also well-established in neurophysiology, from the work of Hubel and Wiesel among others.

Children with developmental delays (DD) are at heightened risk for developing clinically significant behavioral and emotional difficulties as compared to children with typical development (TD). However, nearly all studies comparing psychopathology in youth with DD employ TD control groups of the same chronological age (CA).This comorbidity of DD and a mental disorder is often referred to as dual diagnosis. Epidemiological studies indicate that 30–50% of youth with DD meet the clinical cutoff for behavioral and emotional problems and/or diagnosable mental disorder. Studies that include comparison samples of children with typical development (TD) highlight the considerable difference in risk for psychopathology, with the relative risk for youth with DD (to youth with TD) ranging from 2.8–4.1 to 1.

Infants shift between ages of one and two to a developmental stage known as toddlerhood. In this stage, an infant's transition into toddlerhood is highlighted through self-awareness, developing maturity in language use, and presence of memory and imagination.

During toddlerhood, babies begin learning how to walk, talk, and make decisions for themselves. An important characteristic of this age period is the development of language, where children are learning how to communicate and express their emotions and desires through the use of vocal sounds, babbling, and eventually words. Self-control also begins to develop. At this age, children take initiative to explore, experiment and learn from making mistakes. Caretakers who encourage toddlers to try new things and test their limits, help the child become autonomous, self-reliant, and confident. If the caretaker is overprotective or disapproving of independent actions, the toddler may begin to doubt their abilities and feel ashamed of the desire for independence. The child's autonomic development is inhibited, leaving them less prepared to deal with the world in the future. Toddlers also begin to identify themselves in gender roles, acting according to their perception of what a man or woman should do.

Socially, the period of toddler-hood is commonly called the "terrible twos". Toddlers often use their new-found language abilities to voice their desires, but are often misunderstood by parents due to their language skills just beginning to develop. A person at this stage testing their independence is another reason behind the stage's infamous label. Tantrums in a fit of frustration are also common.

Erik Erikson divides childhood into four stages, each with its distinct social crisis:

Play (or preschool) ages 3–5.
In the earliest years, children are "completely dependent on the care of others." Therefore, they develop a "social relationship" with their care givers and, later, with family members. During their preschool years (3-5), they "enlarge their social horizons" to include people outside the family.

Preoperational and then operational thinking develops, which means actions are reversible, and egocentric thought diminishes.

The motor skills of preschoolers increase so they can do more things for themselves. They become more independent. No longer completely dependent on the care of others, the world of this age group expands. More people have a role in shaping their individual personalities. Preschoolers explore and question their world. For Jean Piaget, the child is ""a little scientist" exploring and reflecting on these explorations to increase competence" and this is done in "a very independent way."

Play is a major activity for ages 3–5. For Piaget, through play "a child reaches higher levels of cognitive development."

In their expanded world, children in the 3-5 age group attempt to find their own way. If this is done in a socially acceptable way, the child develops the initiative. If not, the child develops guilt. Children who develop "guilt" rather than "initiative" have failed Erikson's psychosocial crisis for the 3-5 age group.

Middle childhood ages 6–12.
For Erik Erikson, the psychosocial crisis during middle childhood is Industry vs. Inferiority which, if successfully met, instills a sense of Competency in the child.

In all cultures, middle childhood is a time for developing "skills that will be needed in their society." School offers an arena in which children can gain a view of themselves as "industrious (and worthy)." They are "graded for their school work and often for their industry." They can also develop industry outside of school in sports, games, and doing volunteer work. Children who achieve "success in school or games might develop a feeling of competence."

The "peril during this period is that feelings of inadequacy and inferiority will develop. Parents and teachers can "undermine" a child's development by failing to recognize accomplishments or being overly critical of a child's efforts.
Children who are "encouraged and praised" develop a belief in their competence. Lack of encouragement or ability to excel lead to "feelings of inadequacy and inferiority".

The Centers for Disease Control (the CDC) divides Middle Childhood into two stages, 6–8 years and 9–11 years, and gives "developmental milestones for each stage."

"Middle Childhood (7-10)."
Entering elementary school, children in this age group begin to thinks about the future and their "place in the world." Working with other students and wanting their friendship and acceptance become more important. This leads to "more independence from parents and family." As students, they develop the mental and verbal skills "to describe experiences and talk about thoughts and feelings". They become less self-centered and show "more concern for others".

"Middle Childhood (9-11)."
For children ages 9–11 "friendships and peer relationships" increase in strength, complexity, and importance. This results in greater "peer pressure." They grow even less dependent on their families and they are challenged academically. To meet this challenge, they increase their attention span and learn to see other points of view.

Adolescence is the period of life between the onset of puberty and the full commitment to an adult social role, such as worker, parent, and/or citizen. It is the period known for the formation of personal and social identity (see Erik Erikson) and the discovery of moral purpose (see William Damon). Intelligence is demonstrated through the logical use of symbols related to abstract concepts and formal reasoning. A return to egocentric thought often occurs early in the period. Only 35% develop the capacity to reason formally during adolescence or adulthood. (Huitt, W. and Hummel, J. January 1998)

It is divided into three parts, namely:

The adolescent unconsciously explores questions such as "Who am I? Who do I want to be?" Like toddlers, adolescents must explore, test limits, become autonomous, and commit to an identity, or sense of self. Different roles, behaviors and ideologies must be tried out to select an identity. Role confusion and inability to choose vocation can result from a failure to achieve a sense of identity through, for example, friends.

Early adulthood generally refers to the period between ages 18 to 29, and according to theorists such as Erik Erikson, is a stage where development is mainly focused on maintaining relationships. Examples include creating bond of intimacy, sustaining friendships, and ultimately making a family. Some theorists state that development of intimacy skills rely on the resolution of previous developmental stages. A sense of identity gained in the previous stages is also necessary for intimacy to develop. If this skill is not learned the alternative is alienation, isolation, a fear of commitment, and the inability to depend on others.

A related framework for studying this part of the lifespan is that of emerging adulthood. Scholars of emerging adulthood, such as Jeffrey Arnett, are not necessarily interested in relationship development. Instead, this concept suggests that people transition after their teenage years into a period not characterized as relationship building and an overall sense of constancy with life, but with years of living with parents, phases of self-discovery, and experimentation.

Middle adulthood generally refers to the period between ages 29 to 49. During this period, middle-aged adults experience a conflict between generativity and stagnation. They may either feel a sense of contributing to society, the next generation, or their immediate community; or develop a sense of purposelessness.

Physically, the middle-aged experience a decline in muscular strength, reaction time, sensory keenness, and cardiac output. Also, women experience menopause at an average age of 48.8 and a sharp drop in the hormone estrogen. Men experience an equivalent endocrine system event to menopause. Andropause in males is a hormone fluctuation with physical and psychological effects that can be similar to those seen in menopausal females. As men age lowered testosterone levels can contribute to mood swings and a decline in sperm count. Sexual responsiveness can also be affected, including delays in erection and longer periods of penile stimulation required to achieve ejaculation.

The important influence of biological and social changes experienced by women and men in middle adulthood is reflected in that fact that depression is highest at age 48.5 around the world.

The World Health Organization finds "no general agreement on the age at which a person becomes old." Most "developed countries" set the age as 60 or 65. However, in developing countries inability to make "active contribution" to society, not chronological age, marks the beginning of old age. According to Erikson's stages of psychosocial development, old age is the stage in which individuals assess the quality of their lives. In reflecting on their lives, people in this age group develop a feeling of integrity if deciding that their lives were successful or a feeling of despair if evaluation of one's life indicates a failure to achieve goals.

Physically, older people experience a decline in muscular strength, reaction time, stamina, hearing, distance perception, and the sense of smell. They also are more susceptible to diseases such as cancer and pneumonia due to a weakened immune system. Programs aimed at balance, muscle strength, and mobility have been shown to reduce disability among mildly (but not more severely) disabled elderly.

Sexual expression depends in large part upon the emotional and physical health of the individual. Many older adults continue to be sexually active and satisfied with their sexual activity.

Mental disintegration may also occur, leading to dementia or ailments such as Alzheimer's disease. The average age of onset for dementia in males is 78.8 and 81.9 for women. It is generally believed that crystallized intelligence increases up to old age, while fluid intelligence decreases with age. Whether or not normal intelligence increases or decreases with age depends on the measure and study. Longitudinal studies show that perceptual speed, inductive reasoning, and spatial orientation decline. An article on adult cognitive development reports that cross-sectional studies show that "some abilities remained stable into early old age."

Parenting variables alone have typically accounted for 20 to 50 percent of the variance in child outcomes.

All parents have their own parenting styles. Parenting styles, according to Kimberly Kopko, are "based upon two aspects of parenting behavior; control and warmth. Parental control refers to the degree to which parents manage their children's behavior. Parental warmth refers to the degree to which parents are accepting and responsive to their children's behavior."

The following parenting styles have been described in the child development literature:Parenting roles in child development have typically focused on the role of the mother. Recent literature, however, has looked toward the father as having an important role in child development. Affirming a role for fathers, studies have shown that children as young as 15 months benefit significantly from substantial engagement with their father. In particular, a study in the U.S. and New Zealand found the presence of the natural father was the most significant factor in reducing rates of early sexual activity and rates of teenage pregnancy in girls. Furthermore, another argument is that neither a mother nor a father is actually essential in successful parenting, and that single parents as well as homosexual couples can support positive child outcomes. According to this set of research, children need at least one consistently responsible adult with whom the child can have a positive emotional connection. Having more than one of these figures contributes to a higher likelihood of positive child outcomes.

Another parental factor often debated in terms of its effects on child development is divorce. Divorce in itself is not a determining factor of negative child outcomes. In fact, the majority of children from divorcing families fall into the normal range on measures of psychological and cognitive functioning. A number of mediating factors play a role in determining the effects divorce has on a child, for example, divorcing families with young children often face harsher consequences in terms of demographic, social, and economic changes than do families with older children. Positive coparenting after divorce is part of a pattern associated with positive child coping, while hostile parenting behaviors lead to a destructive pattern leaving children at risk. Additionally, direct parental relationship with the child also affects the development of a child after a divorce. Overall, protective factors facilitating positive child development after a divorce are maternal warmth, positive father-child relationship, and cooperation between parents.Prominent journals in developmental psychology include:

Whilst Bowlby's early writings on maternal deprivation may be seen as part of the background to the later development of attachment theory, there are many significant differences between the two. At the time of the 1951 publication, there was little research in this area and no comprehensive theory on the development of early relationships. Aside from its central proposition of the importance of an early, continuous and sensitive relationship, the monograph concentrates mostly on social policy. For his subsequent development of attachment theory, Bowlby drew on concepts from ethology, cybernetics, information processing, developmental psychology and psychoanalysis. The first early formal statements of attachment theory were presented in three papers in 1958, 1959 and 1960. His major work "Attachment" was published in three volumes between 1969 and 1980. Attachment theory revolutionised thinking on the nature of early attachments and extensive research continues to be undertaken.

Maternal deprivation

The term maternal deprivation is a scientific term summarising the early work of psychiatrist and psychoanalyst, John Bowlby on the effects of separating infants and young children from their mother (or mother substitute) although the effect of loss of the mother on the developing child had been considered earlier by Freud and other theorists. Bowlby's work on delinquent and affectionless children and the effects of hospital and institutional care led to his being commissioned to write the World Health Organization's report on the mental health of homeless children in post-war Europe whilst he was head of the Department for Children and Parents at the Tavistock Clinic in London after World War II. The result was the monograph "Maternal Care and Mental Health" published in 1951, which sets out the maternal deprivation hypothesis.

Bowlby drew together such empirical evidence as existed at the time from across Europe and the US, including Spitz (1946) and Goldfarb (1943, 1945). His main conclusions, that "the infant and young child should experience a warm, intimate, and continuous relationship with his mother (or permanent mother substitute) in which both find satisfaction and enjoyment" and that not to do so might have significant and irreversible mental health consequences, were both controversial and influential. The monograph was published in 14 different languages and sold over 400,000 copies in the English version alone. Bowlby's work went beyond the suggestions of Otto Rank and Ian Suttie that mothering care was essential for development, and focused on the potential outcomes for children deprived of such care.

The 1951 WHO publication was highly influential in causing widespread changes in the practices and prevalence of institutional care for infants and children, and in changing practices relating to the stays of small children in hospitals so that parents were allowed more frequent and longer visits. Although the monograph was primarily concerned with the removal of children from their homes it was also used for political purposes to discourage women from working and leaving their children in daycare by governments concerned about maximising employment for returned and returning servicemen. The publication was also highly controversial with, amongst others, psychoanalysts, psychologists and learning theorists, and sparked significant debate and research on the issue of children's early relationships.

The limited empirical data and lack of comprehensive theory to account for the conclusions in "Maternal Care and Mental Health" led to the subsequent formulation of attachment theory by Bowlby. Following the publication of "Maternal Care and Mental Health" Bowlby sought new understanding from such fields as evolutionary biology, ethology, developmental psychology, cognitive science and control systems theory and drew upon them to formulate the innovative proposition that the mechanisms underlying an infant's ties emerged as a result of evolutionary pressure. Bowlby claimed to have made good the "deficiencies of the data and the lack of theory to link alleged cause and effect" in "Maternal Care and Mental Health" in his later work "Attachment and Loss" published between 1969 and 1980.

Although the central tenet of maternal deprivation theory—that children's experiences of interpersonal relationships are crucial to their psychological development and that the formation of an ongoing relationship with the child is as important a part of parenting as the provision of experiences, discipline and child care—has become generally accepted, "maternal deprivation" as a discrete syndrome is not a concept that is much in current use other than in relation to severe deprivation as in "failure to thrive". In the area of early relationships it has largely been superseded by attachment theory and other theories relating to even earlier infant–parent interactions. As a concept, parental deficiencies are seen as a vulnerability factor for, rather than a direct cause of, later difficulties. In relation to institutional care there has been a great deal of subsequent research on the individual elements of privation, deprivation, understimulation and deficiencies that may arise from institutional care.

Scientific research has stressed the grief of mothers over deprivation of their children but little has been said historically about young children's loss of their mothers; this may have been because loss of the mother in infancy frequently meant death for a breast-fed infant. In the 19th century, French society bureaucratised a system in which infants were breast-fed at the homes of foster mothers, returning to the biological family after weaning, and no concern was evinced at the possible effect of this double separation on the child.

Sigmund Freud may have been among the first to stress the potential effect of loss of the mother on the developing child, but his concern was less with the actual experience of maternal care than with the anxiety the child might feel about the loss of the nourishing breast. As little of Freud's theory was based on actual observations of infants, little effort was made to consider the effects of real experiences of loss.
Following Freud's early speculations about infant experience with the mother, Otto Rank suggested a powerful role in personality development for birth trauma. Rank stressed the traumatic experience of birth as a separation from the mother, rather than birth as an uncomfortable physical event. Not long after Rank's introduction of this idea, Ian Suttie, a British physician whose early death limited his influence, suggested that the child's basic need is for mother-love, and his greatest anxiety is that such love will be lost.

In the 1930s, David Levy noted a phenomenon he called "primary affect hunger" in children removed very early from their mothers and brought up in institutions and multiple foster homes. These children, though often pleasant on the surface, seemed indifferent underneath. He questioned whether there could be a "deficiency disease of the emotional life, comparable to a deficiency of vital nutritional elements within the developing organism". A few psychiatrists, psychologists and paediatricians were also concerned by the high mortality rate in hospitals and institutions obsessed with sterility to the detriment of any human or nurturing contact with babies. One rare paediatrician went so far as to replace a sign saying "Wash your hands twice before entering this ward" with one saying "Do not enter this nursery without picking up a baby".

In a series of studies published in the 1930s, psychologist Bill Goldfarb noted not only deficits in the ability to form relationships, but also in the IQ of institutionalised children as compared to a matched group in foster care. In another study conducted in the 1930s, Harold Skeels, noting the decline in IQ in young orphanage children, removed toddlers from a sterile orphanage and gave them to "feeble-minded" institutionalised older girls to care for. The toddlers' IQ rose dramatically. Skeels study was attacked for lack of scientific rigour though he achieved belated recognition decades later.

René Spitz, a psychoanalyst, undertook research in the 1930s and '40s on the effects of maternal deprivation and "hospitalism". His investigation focused on infants who had experienced abrupt, long-term separation from the familiar caregiver, as, for instance, when the mother was sent to prison. These studies and conclusions were thus different from the investigations of institutional rearing. Spitz adopted the term "anaclitic depression" to describe the child's reaction of grief, anger, and apathy to partial emotional deprivation (the loss of a loved object) and proposed that when the love object is returned to the child within three to five months, recovery is prompt but after five months, they will show the symptoms of increasingly serious deterioration. He called this reaction to total deprivation "hospitalism". He was also one of the first to undertake direct observation of infants. The conclusions were hotly disputed and there was no widespread acceptance.

During the years of World War II, evacuated and orphaned children were the subjects of studies that outlined their reactions to separation, including the ability to cope by forming relationships with other children. Some of this material remained unpublished until the post-war period and only gradually contributed to understanding of young children's reactions to loss.

Bowlby, who, unlike most psychoanalysts, had direct experience of working with deprived children through his work at the London Child Guidance Clinic, called for more investigation of children's early lives in a paper published in 1940. He proposed that two environmental factors were paramount in early childhood. The first was death of the mother, or prolonged separation from her. The second was the mother's emotional attitude towards her child. This was followed by a study on forty–four juvenile thieves collected through the Clinic. There were many problematic parental behaviours in the samples but Bowlby was looking at one environmental factor that was easy to document, namely prolonged early separations of child and mother. Of the forty-four thieves, fourteen fell into the category which Bowlby characterised as being of an "affectionless character". Of these fourteen, twelve had suffered prolonged maternal separations as opposed to only two of the control group.

An NIH study published in 2011 examined the impact of short, non-traumatic separation from the child's primary caregiver. The subjects were infants separated from their primary caregiver for at least a week. Controlling for various factors including income, stability, and parenting style, the study found increased aggressiveness at ages 3 and 5 in separated infants, but it did not find other cognitive impairment. Most infants in the study stayed with close relatives or the other parent, often in the infant's home, suggesting that even in ideal circumstances, maternal separation can have lasting detrimental impact on infant development.

Bowlby's work on delinquent and affectionless children and the effects of hospital and institutional care lead to his being commissioned to write the World Health Organization's report on the mental health of homeless children in post-war Europe whilst he was head of the Department for Children and Parents at the Tavistock Clinic in London after World War II. Bowlby travelled on the Continent and in America, communicating with social workers, paediatricians and child psychiatrists including those who had already published literature on the issue. These authors were mainly unaware of each other's work, and Bowlby was able to draw together the findings and highlight the similarities described, despite the variety of methods used, ranging from direct observation to retrospective analysis to comparison groups. In addition, there was work from England undertaken by Dorothy Burlingham and Anna Freud on children separated from their families due to wartime disruption, and Bowlby's own work. The result was the monograph "Maternal Care and Mental Health" published in 1951, which sets out the maternal deprivation hypothesis. The WHO report was followed by the publication of an abridged version for public consumption called "Child Care and the Growth of Love". This book sold over half a million copies worldwide. Bowlby tackled not only institutional and hospital care, but also policies of removing children from "unwed mothers" and untidy and physically neglected homes, and lack of support for families in difficulties. In a range of areas Bowlby cited the lack of adequate research and suggested the direction this could take.

The quality of parental care was considered by Bowlby to be of vital importance to the child's development and future mental health. It was believed to be essential that the infant and young child should experience a warm, intimate, and continuous relationship with his mother (or permanent mother substitute) in which both found satisfaction and enjoyment. Given this relationship, emotions of guilt and anxiety (characteristics of mental illness when in excess) would develop in an organised and moderate way. Naturally extreme emotions would be moderated and become amenable to the control of the child's developing personality. He stated, "It is this complex rich and rewarding relationship with the mother in the early years, varied in countless ways by relations with the father and with siblings, that child psychiatrists and many others now believe to underlie the development of character and mental health."
The state of affairs in which the child did not have this relationship he termed "maternal deprivation". This term covered a range from almost complete deprivation, not uncommon in institutions, residential nurseries and hospitals, to partial deprivation where the mother, or mother substitute, was unable to give the loving care a small child needs, to mild deprivation where the child was removed from the mother's care but was looked after by someone familiar whom he trusted. Complete or almost complete deprivation could "entirely cripple the capacity to make relationships". Partial deprivation could result in acute anxiety, depression, neediness and powerful emotions which the child could not regulate. The end product of such psychic disturbance could be neurosis and instability of character. However, the main focus of the monograph was on the more extreme forms of deprivation. The focus was the child's developing relationships with his mother and father and disturbed parent–child relationships in the context of almost complete deprivation rather than the earlier concept of the "broken home" as such.

In terms of social policy, Bowlby advised that parents should be supported by society as parents are dependent on a greater society for economic provision and "if a community values its children it must cherish its parents". Also "husbandless" mothers of children under 3 should be supported to care for the child at home rather than the child be left in inadequate care whilst the mother sought work. (It was assumed the mother of the illegitimate child would usually be left with the child). Fathers left with infants or small children on their hands without the mother should be provided with "housekeepers" so that the children could remain at home. Other proposals included the proper payment of foster homes and careful selection of foster carers, and frank, informative discussions with children about their parents and why they ended up in care and how they felt about it rather than the "least said, soonest mended" approach. The point that children were loyal to and loved even the worst of parents, and needed to have that fact understood non-judgementally, was strongly made.

On the issue of removal of children from their homes, Bowlby emphasised the strength of the tie that children feel towards their parents and discussed the reason why, as he put it, "children thrive better in bad homes than in good institutions". He was strongly in favour of support being provided to parents and extended families to improve the situation and provide care within the family rather than removal if possible.

Bowlby used the phrase "mother (or permanent mother substitute)". As it is commonly used, the term maternal deprivation is ambiguous as it is unclear whether the deprivation is that of the biological mother, of an adoptive or foster mother, a consistent caregiving adult of any gender or relationship to the child, of an emotional relationship, or of the experience of the type of care called "mothering" in many cultures. Questions about the exact meaning of this term are by no means new, as the following statement by Mary Ainsworth in 1962 indicates: "Although in the early months of life it is the mother who almost invariably interacts most with the child... the role of other figures, especially the father, is acknowledged to be significant... [P]aternal deprivation... has received scant attention... [In the case of] institutionalization... the term 'parental deprivation' would have been more accurate, for the child has been... deprived of interaction with a father-figure as well as a mother-figure... [It may be better to] discourage the use of [the term 'deprivation'] and encourage the substitution of the terms 'insufficiency', 'discontinuity', and 'distortion' instead." Ainsworth implies, neither the word "maternal" nor the word "deprivation" seems to be a literally correct definition of the phenomenon under consideration.

A contemporary of Ainsworth spoke of "the mother, a term by which we mean both the child's actual mother and/or any other person of either sex who may take the place of the child's physical mother during a significant period of time". However, another contemporary referred to "the quasi-mystical union of mother and child, of the dynamic union that mother and child represent".

The practical effects of the publication of "Maternal Care and Mental Health" were described in the preface to the WHO 1962 publication "Deprivation of Maternal Care: A Reassessment of its Effects" as "almost wholly beneficial" with reference to widespread changes in the institutional care of children.
The practice of allowing parents frequent visiting to hospitalised children became the norm and there was a move towards placing homeless children with foster carers, rather than in institutions, and a move towards the professionalisation of alternative carers. In hospitals, the change was given added impetus by the work of social worker and psychoanalyst James Robertson who filmed the distressing effects of separation on children in hospital and collaborated with Bowlby in making the 1952 documentary film "A Two-Year Old Goes to the Hospital".

According to Michael Rutter, the importance of Bowlby's initial writings on "maternal deprivation" lay in his emphasis that children's experiences of interpersonal relationships were crucial to their psychological development and that the formation of an ongoing relationship with the child was as important a part of parenting as the provision of experiences, discipline and child care. Although this view was rejected by many at the time, the argument focussed attention on the need to consider parenting in terms of consistency of caregivers over time and parental sensitivity to children's individuality and it is now generally accepted. Bowlby's theory sparked considerable interest and controversy in the nature of early relationships and gave a strong impetus to what Mary Ainsworth described as a "great body of research" in what was perceived as an extremely difficult and complex area.

Bowlby departed from psychoanalytical theory which saw the gratification of sensory needs as the basis for the relationship between infant and mother. Food was seen as the primary drive and the relationship, or "dependency" was secondary. He had already found himself in conflict with dominant Kleinian theories that children's emotional problems are almost entirely due to fantasies generated from internal conflict between aggressive and libidinal drives, rather than to events in the external world. (His breach with the psychoanalysts only became total and irreparable after his later development of attachment theory incorporating ethological and evolutionary principles, when he was effectively ostracised). Bowlby also broke with social learning theory's view of dependency and reinforcement. Bowlby proposed instead that to thrive emotionally, children needed a close and continuous caregiving relationship.

Bowlby later stated that he had concluded that, contrary to the focus of psychoanalysts on the internal fantasy world of the child, the important area to study was how a child was actually treated by his parents in real life and in particular the interaction between them. He chose the actual removal of children from the home at this particular time because it was a specific event, the effects of which could be studied, and because he believed it could have serious effects on a child's development and because it was preventable. In addition, views that he had already expressed about the importance of a child's real life experiences and relationship with carers had been met by "sheer incredulity" by colleagues before World War II. This led him to see that far more systematic knowledge was required of the effects on a child of early experiences. Bowlby and his colleagues were pioneers of the view that studies involving direct observation of infants and children were not merely of interest but were essential to the advancement of science in this area.

Researchers have for years studied depression, alcoholism, aggression, maternal-infant bonding and other conditions and phenomena in nonhuman primates and other laboratory animals using an experimental maternal deprivation paradigm. Most influentially, Harry Harlow would, in the mid-1950s, begin raising infant monkeys in his University of Wisconsin–Madison laboratory in total or partial isolation and with inanimate surrogate mothers in an attempt to study maternal-infant bonding as well as various states of mental illness.

In Harlow's laboratory, infant rhesus monkeys were immediately removed from their mothers and placed with cloth or wire surrogate mothers, sometimes called "iron maidens" by the researchers. Harlow found that the infants would become attached to their inanimate mothers—both those made of wire and those covered with cloth—and when removed from them they would "screech in terror". Harlow and his colleagues would later develop "evil artificial mothers" meant to "impart fear and insecurity to infant monkeys"—including one designed with brass spikes—but contrary to the researcher's hypothesis, these animals too demonstrated an attachment to their surrogates.

Subsequent experiments would study the effects of total and partial isolation on the animals' mental health and interpersonal bonding using a stainless steel vertical chamber designed by Harlow, named the "pit of despair", which was found to produce "profound and prolonged depression" in monkeys. Similarly, Harlow found that extended isolation in bare wire cages left monkeys with "profound behavioral abnormalities" including "self-clutching and rocking" and later "apathy and indifference to external stimulation". Harlow likened this behavior to catatonic schizophrenia.
Later experiments were devised to test the mother-child bond with mothers who had themselves been reared in isolation as infants. This early deprivation was found to have retarded the mothers' emotional development and her ability to engage in intercourse and in turn become pregnant. In response, Harlow and his colleagues created an apparatus to impregnate these mothers they named a "rape rack". Harlow found that once these monkeys gave birth, they cared little for their offspring writing, "these monkey mothers that had never experienced love of any kind were devoid of love for their infants". While some mothers simply ignored their children, Harlow characterized others as "evil" and abusive and in some instances reported them "crushing the infant's face to the floor, chewing off the infant's feet and fingers, and in one case... putting the infant's head in her mouth and crushing it like an eggshell".

Harlow's experiments have been heralded as revolutionary and also robustly criticized as scientifically invalid and sadistically cruel. Writing on the researcher's legacy, John Gluck, a former student of Harlow's opined, "On the one hand, his work on monkey cognition and social development fostered a view of the animals as having rich subjective lives filled with intention and emotion. On the other, he has been criticized for the conduct of research that seemed to ignore the ethical implantations of his own discoveries."

Maternal deprivation experiments on nonhuman primates have continued into the 21st century and remain controversial. Stephen Suomi, an early collaborator of Harlow, has continued to conduct maternal deprivation experiments on rhesus monkeys in his NIH laboratory and has been vigorously criticized by PETA, Members of Congress and others.

Aside from his profound differences with psychoanalytic ideas, the theoretical basis of Bowlby's monograph was controversial in a number of ways. Some profoundly disagreed with the necessity for maternal (or equivalent) love in order to function normally, or that the formation of an ongoing relationship with a child was an important part of parenting. The idea that early experiences have serious consequences for intellectual and psychosocial development was controversial in itself. Others questioned the extent to which his hypothesis was supported by the evidence. There was criticism of the confusion of the effects of "privation" (no primary attachment figure) and "deprivation" (loss of the primary attachment figure) and in particular, of the failure to distinguish between the effects of the lack of a primary attachment figure and the other forms of deprivation and understimulation that might affect children in institutions.

It was also pointed out that there was no explanation of how experiences subsumed under the broad heading of "maternal deprivation" could have effects on personality development of the kinds claimed. Bowlby explained in his 1988 work that the data were not at the time "accommodated by any theory then current and in the brief time of my employment by the World Health Organization there was no possibility of developing a new one". He then goes on to describe the subsequent development of attachment theory.

In addition to criticism, his ideas were often oversimplified, misrepresented, distorted or exaggerated for various purposes. This heightened the controversy. In 1962, the WHO published "Deprivation of Maternal Care: A Reassessment of its Effects" to which Mary Ainsworth, Bowlby's close colleague, contributed with his approval, to present the recent research and developments and to address misapprehensions.

Bowlby's work was misinterpreted to mean that "any" separation from the natural mother, "any" experience of institutional care or a multiplicity of "mothers" necessarily resulted in severe emotional deprivation and sometimes, that "all" children undergoing such experiences would develop into "affectionless children". As a consequence it was claimed that only 24-hour care by the same person (the mother) was good enough, day care and nurseries were not good enough and mothers should not go out to work. The WHO advised that day nurseries and creches could have a serious and permanent deleterious effect. Such strictures suited the policies of governments concerned about finding employment for returned and returning servicemen after World War II. In fact, although Bowlby was of the view that proper care could not be provided "by roster", he was also of the view that babies should be accustomed to regular periods of care by another and that the key to alternative care for working mothers was that it should be regular and continuous. He addressed this point in a 1958 publication called "Can I Leave My Baby?". Ainsworth in the WHO 1962 publication also attempted to address this misapprehension by pointing out that the requirement for continuity of care did not imply an exclusive mother–child pair relationship.

Bowlby's quotable remark, that children thrived better in bad homes than in good institutions, was often taken to extremes leading to reluctance on the part of Children's Officers (the equivalent of child care social workers) to remove children from homes however neglectful and inadequate. In fact, although Bowlby mentioned briefly the issue of "partial deprivation" within the family, this was not fully investigated in his monograph as the main focus was on the risks of complete or almost complete deprivation.

Michael Rutter made a significant contribution to the controversial issue of Bowlby's maternal deprivation hypothesis. His 1981 monograph and other papers comprise the definitive empirical evaluation and update of Bowlby's early work on maternal deprivation. He amassed further evidence, addressed the many different underlying social and psychological mechanisms and showed that Bowlby was only partially right and often for the wrong reasons. Rutter highlighted the other forms of deprivation found in institutional care and the complexity of separation distress; and suggested that anti-social behaviour was not linked to maternal deprivation as such but to family discord. The importance of these refinements of the maternal deprivation hypothesis was to reposition it as a "vulnerability factor" rather than a causative agent, with a number of varied influences determining which path a child would take.

Rutter has more recently advised attention to the complexity of development and the roles of genetic as well as experiential factors, noting that separation is only one of many risk factors related to poor cognitive and emotional development.

In accordance with the prevailing social realities of his time, namely the assumption that the daily care of infants and small children was undertaken by women and in particular, mothers, Bowlby referred primarily to mothers and "maternal" deprivation, although the words "parents" and "parental" are also used. Fathers are mentioned only in the context of the practical and emotional support they provide for the mother but the monograph contains no specific exploration of the father's role. Nor is there any discussion as to whether the maternal role had, of necessity, to be filled by "women" as such. Bowlby's work was misinterpreted by some to mean "natural" mothers only.

The 1962 WHO publication contains a chapter on the effect of "paternal deprivation", there having by 1962 been some limited research on the issue which illustrated the importance of the father's relationship with his children. The hope was expressed by Ainsworth that in the future there would be more such research and indeed her early research, which contributed significantly to attachment theory, covered infants relationships with all family members. It was also stated that in relation to institutional care, "parental deprivation" would have been more accurate, although Ainsworth preferred the terms "insufficiency", "discontinuity" and "distortion" to either.

Michael Rutter in "Maternal Deprivation Reassessed" (1972), described by New Society as a "classic in the field of child care", argued that research showed that it did not matter which parent the child got on well with as long as he got on well with one of them, that both parents influence their child's development and that which parent is more important varies with age, sex and temperamental development. He concluded, "For some aspects of development the same-sexed parent seems to have a special role, for some the person who plays and talks most with the child and for others the person who feeds the child. The father, the mother, brother and sisters, friends, school-teachers and others all affect development, but their influences and importance differ for different aspects of development. A less exclusive focus on the mother is required. Children also have fathers!"

Within attachment theory, Bowlby, in "Attachment and Loss", volume one of "Attachment" (1969), makes it quite clear that infants become attached to "carers" who are sensitive and responsive in their social interactions with them and that this does not have to be the mother or indeed a female. As a matter of social reality mothers are more often the primary carers of children and therefore are more likely to be the primary attachment figure, but the process of attachment applies to any carer and infants develop a number of attachments according to who relates to them and the intensity of the engagement. However, attachment theory relates to the development of attachment behaviours and relationships after about 7 months of age and there are other theories and research relating to earlier carer–infant interactions.

Schaffer in "Social Development" (1996) suggests that the father–child relationship is primarily a cultural construction shaped by the requirements of each society. In societies where the care of infants has been assigned to boys rather than girls, no difference in nurturing capacity was found. Other studies, however, point in the opposite direction.

There were three broad criticisms aimed at the idea of maternal deprivation from feminist critics. The first was that Bowlby overstated his case. The studies on which he based his conclusions involved almost complete lack of maternal care and it was unwarranted to generalise from this view that any separation in the first three years of life would be damaging. Subsequent research showed good quality care for part of the day to be harmless. The idea of "exclusive" care or exclusive attachment to a preferred figure, rather than a hierarchy (subsequently thought to be the case within developments of attachment theory) had not been borne out by research and this view placed too high an emotional burden on the mother. Secondly, they criticised Bowlby's historical perspective and saw his views as part of the idealisation of motherhood and family life after World War II. Certainly his hypothesis was used by governments to close down much needed residential nurseries although governments did not seem so keen to pay mothers to care for their children at home as advocated by Bowlby. Thirdly, feminists objected to the idea of anatomy as destiny and concepts of "naturalness" derived from ethnocentric observations. They argued that anthropology showed that it is normal for childcare to be shared by a stable group of adults of which maternal care is an important but not exclusive part.

Whilst Bowlby's early writings on maternal deprivation may be seen as part of the background to the later development of attachment theory, there are many significant differences between the two. At the time of the 1951 publication, there was little research in this area and no comprehensive theory on the development of early relationships. Aside from its central proposition of the importance of an early, continuous and sensitive relationship, the monograph concentrates mostly on social policy. For his subsequent development of attachment theory, Bowlby drew on concepts from ethology, cybernetics, information processing, developmental psychology and psychoanalysis. The first early formal statements of attachment theory were presented in three papers in 1958, 1959 and 1960. His major work "Attachment" was published in three volumes between 1969 and 1980. Attachment theory revolutionised thinking on the nature of early attachments and extensive research continues to be undertaken.

According to Zeanah, "ethological attachment theory, as outlined by John Bowlby... 1969 to 1980... has provided one of the most important frameworks for understanding crucial risk and protective factors in social and emotional development in the first 3 years of life. Bowlby's (1951) monograph, Maternal Care and Mental Health, reviewed the world literature on maternal deprivation and suggested that emotionally available caregiving was crucial for infant development and mental health." Beyond that broad statement, which is now generally accepted, little remains of the underlying detail of Bowlby's theory of maternal deprivation that has not been either discredited or superseded by attachment theory and other child development theories and research, except in the area of extreme deprivation.

The opening of East European orphanages in the early 1990s following the end of the Cold War provided substantial opportunities for research on attachment and other aspects of institutional rearing, however such research rarely mentions "maternal deprivation" other than in a historical context. Maternal deprivation as a discrete syndrome is a concept that is rarely used other than in connection with extreme deprivation and failure to thrive. Rather there is consideration of a range of different lacks and deficiencies in different forms of care, or lack of care, of which attachment is only one aspect, as well as consideration of constitutional and genetic factors in determining developmental outcome. Subsequent studies have however confirmed Bowlby's concept of "cycles of disadvantage" although not all children from unhappy homes reproduce the deficiencies in their own experience. Rather, it is now conceptualised as a series of pathways through childhood and a number of varied influences will determine which path a particular child takes.

The idea that separation from the female caregiver has profound effects is one with considerable resonance outside the conventional study of child development. In United States law, the "tender years" doctrine was long applied when custody of infants and toddlers was preferentially given to mothers. Over the last decade or so, some decisions appear to have been derived from the "tender years" concept, but others involve the contrary assumption that a 2-year-old is too young to have developed a relationship with either parent.

Concern with the harm of separation from the mother is characteristic of the belief systems behind some complementary and alternative (CAM) psychotherapies. Such belief systems are concerned not only with the effect of the young child's separation from the care of the mother, but with an emotional attachment between mother and child which advocates of these systems believe to develop prenatally. Such attachment is said to lead to emotional trauma if the child is separated from the birth mother and adopted, even if this occurs on the day of birth and even if the adoptive family provides all possible love and care. These beliefs were at one time in existence among psychologists of psychoanalytic background. Today, however, beliefs in prenatal communication between mothers and infants are largely confined to unconventional thinkers such as William Emerson.

Belief in prenatal fetal awareness, mental communication between mother and unborn child, and emotional attachment of child to mother as a prenatal phenomenon, are concepts that connect easily to the unfounded assumption that all adopted children suffer emotional disorders. These beliefs are also congruent with CAM psychotherapies such as attachment therapy (not based on attachment theory), which purport to bring about age regression and to recapitulate early development to produce a better outcome.

The broad theoretical framework for current versions of RAD is attachment theory, based on work conducted from the 1940s to the 1980s by John Bowlby, Mary Ainsworth and René Spitz. Attachment theory is a framework that employs psychological, ethological and evolutionary concepts to explain social behaviors typical of young children. Attachment theory focuses on the tendency of infants or children to "seek proximity" to a "particular attachment figure" (familiar caregiver), in situations of alarm or distress, behavior which appears to have survival value. This is known as a discriminatory or selective attachment. Subsequently, the child begins to use the caregiver as a base of security from which to explore the environment, returning periodically to the familiar person. Attachment is not the same as love and/or affection although they are often associated. Attachment and attachment behaviors tend to develop between the ages of six months and three years. Infants become attached to adults who are sensitive and responsive in social interactions with the infant, and who remain as consistent caregivers for some time. Caregiver responses lead to the development of patterns of attachment, that in turn lead to internal working models which will guide the individual's feelings, thoughts, and expectations in later relationships. For a diagnosis of reactive attachment disorder, the child's history and atypical social behavior must suggest the absence of formation of a discriminatory or selective attachment.

Reactive attachment disorder

Reactive attachment disorder (RAD) is described in clinical literature as a severe and relatively uncommon disorder that can affect children. RAD is characterized by markedly disturbed and developmentally inappropriate ways of relating socially in most contexts. It can take the form of a persistent failure to initiate or respond to most social interactions in a developmentally appropriate way—known as the "inhibited form". Due to recent revision in the DSM-5 the "disinhibited form" is now considered a separate diagnosis named "disinhibited attachment disorder".

RAD arises from a failure to form normal attachments to primary caregivers in early childhood. Such a failure could result from severe early experiences of neglect, abuse, abrupt separation from caregivers between the ages of six months and three years, frequent change of caregivers, or a lack of caregiver responsiveness to a child's communicative efforts. Not all, or even a majority of such experiences, result in the disorder. It is differentiated from pervasive developmental disorder or developmental delay and from possibly comorbid conditions such as intellectual disability, all of which can affect attachment behavior. The criteria for a diagnosis of a reactive attachment "disorder" are very different from the criteria used in assessment or categorization of attachment "styles" such as insecure or disorganized attachment.

Children with RAD are presumed to have grossly disturbed internal working models of relationships that may lead to interpersonal and behavioral difficulties in later life. There are few studies of long-term effects, and there is a lack of clarity about the presentation of the disorder beyond the age of five years. However, the opening of orphanages in Eastern Europe following the end of the Cold War in the early-1990s provided opportunities for research on infants and toddlers brought up in very deprived conditions. Such research broadened the understanding of the prevalence, causes, mechanism and assessment of disorders of attachment and led to efforts from the late-1990s onwards to develop treatment and prevention programs and better methods of assessment. Mainstream theorists in the field have proposed that a broader range of conditions arising from problems with attachment should be defined beyond current classifications.

Mainstream treatment and prevention programs that target RAD and other problematic early attachment behaviors are based on attachment theory and concentrate on increasing the responsiveness and sensitivity of the caregiver, or if that is not possible, placing the child with a different caregiver. Most such strategies are in the process of being evaluated. Mainstream practitioners and theorists have presented significant criticism of the diagnosis and treatment of alleged reactive attachment disorder or the theoretically baseless "attachment disorder" within the controversial form of psychotherapy commonly known as attachment therapy. Attachment therapy has a scientifically unsupported theoretical base and uses diagnostic criteria or symptom lists markedly different to criteria under ICD-10 or DSM-IV-TR, or to attachment behaviors. A range of treatment approaches are used in attachment "therapy", some of which are physically and psychologically coercive, and considered to be antithetical to attachment "theory". Many constitute abuse.

Pediatricians are often the first health professionals to assess and raise suspicions of RAD in children with the disorder. The initial presentation varies according to the child's developmental and chronological age, although it always involves a disturbance in social interaction. Infants up to about 18–24 months "may" present with non-organic failure to thrive and display abnormal responsiveness to stimuli. Laboratory investigations will be unremarkable barring possible findings consistent with malnutrition or dehydration, while serum growth hormone levels will be normal or elevated.

The core feature is severely inappropriate social relating by affected children. This can manifest itself in three ways:While RAD occurs in relation to neglectful and abusive treatment, automatic diagnoses on this basis alone cannot be made, as children can form stable attachments and social relationships despite marked abuse and neglect. However, the instances of that ability are rare.

The name of the disorder emphasizes problems with attachment but the criteria includes symptoms such as failure to thrive, a lack of developmentally appropriate social responsiveness, apathy, and onset before 8 months.

There is as yet no universally accepted diagnostic protocol for reactive attachment disorder. Often a range of measures is used in research and diagnosis. Recognized assessment methods of attachment styles, difficulties or disorders include the Strange Situation Procedure (devised by developmental psychologist Mary Ainsworth), the separation and reunion procedure and the Preschool Assessment of Attachment, the Observational Record of the Caregiving Environment, the Attachment Q-sort and a variety of narrative techniques using stem stories, puppets or pictures. For older children, actual interviews such as the Child Attachment Interview and the Autobiographical Emotional Events Dialogue can be used. Caregivers may also be assessed using procedures such as the Working Model of the Child Interview.

More recent research also uses the Disturbances of Attachment Interview (DAI) developed by Smyke and Zeanah (1999). The DAI is a semi-structured interview designed to be administered by clinicians to caregivers. It covers 12 items, namely "having a discriminated, preferred adult", "seeking comfort when distressed", "responding to comfort when offered", "social and emotional reciprocity", "emotional regulation", "checking back after venturing away from the care giver", "reticence with unfamiliar adults", "willingness to go off with relative strangers", "self-endangering behavior", "excessive clinging", "vigilance/hypercompliance" and "role reversal". This method is designed to pick up not only RAD but also the proposed new alternative categories of disorders of attachment.

Although increasing numbers of childhood mental health problems are being attributed to genetic defects, reactive attachment disorder is by definition based on a problematic history of care and social relationships. Abuse can occur alongside the required factors, but on its own does not explain attachment disorder. It has been suggested that types of temperament, or constitutional response to the environment, may make some individuals susceptible to the stress of unpredictable or hostile relationships with caregivers in the early years. In the absence of available and responsive caregivers it appears that most children are particularly vulnerable to developing attachment disorders.

While similar abnormal parenting may produce the two distinct forms of the disorder, inhibited and disinhibited, studies show that the abuse and neglect was far more prominent and severe in the cases of RAD, disinhibited type. The issue of temperament and its influence on the development of attachment disorders has yet to be resolved. RAD has never been reported in the absence of serious environmental adversity yet outcomes for children raised in the same environment are the same.

In discussing the neurobiological basis for attachment and trauma symptoms in a seven-year twin study, it has been suggested that the roots of various forms of psychopathology, including RAD, Borderline Personality Disorder (BPD), and post-traumatic stress disorder (PTSD), can be found in disturbances in affect regulation. The subsequent development of higher-order self-regulation is jeopardized and the formation of internal models is affected. Consequently, the "templates" in the mind that drive organized behavior in relationships may be impacted. The potential for "re-regulation" (modulation of emotional responses to within the normal range) in the presence of "corrective" experiences (normative caregiving) seems possible.

RAD is one of the least researched and most poorly understood disorders in the DSM. There is little systematic epidemiologic information on RAD, its course is not well established and it appears difficult to diagnose accurately. There is a lack of clarity about the presentation of attachment disorders over the age of five years and difficulty in distinguishing between aspects of attachment disorders, disorganized attachment or the consequences of maltreatment.

According to the American Academy of Child and Adolescent Psychiatry (AACAP), children who exhibit signs of reactive attachment disorder need a comprehensive psychiatric assessment and individualized treatment plan. The signs or symptoms of RAD may also be found in other psychiatric disorders and AACAP advises against giving a child this label or diagnosis without a comprehensive evaluation. Their practice parameter states that the assessment of reactive attachment disorder requires evidence directly obtained from serial observations of the child interacting with his or her primary caregivers and history (as available) of the child’s patterns of attachment behavior with these caregivers. It also requires observations of the child’s behavior with unfamiliar adults and a comprehensive history of the child’s early caregiving environment including, for example, pediatricians, teachers, or caseworkers. In the US, initial evaluations may be conducted by psychologists, psychiatrists, Licensed Marriage and Family Therapists, Licensed Professional Counselors, specialist Licensed Clinical Social Workers or psychiatric nurses.

In the UK, the British Association for Adoption and Fostering (BAAF) advise that only a psychiatrist can diagnose an attachment disorder and that any assessment must include a comprehensive evaluation of the child’s individual and family history.

According to the AACAP Practice Parameter (2005) the question of whether attachment disorders can reliably be diagnosed in older children and adults has not been resolved. Attachment behaviors used for the diagnosis of RAD change markedly with development and defining analogous behaviors in older children is difficult. There are no substantially validated measures of attachment in middle childhood or early adolescence. Assessments of RAD past school age may not be possible at all as by this time children have developed along individual lines to such an extent that early attachment experiences are only one factor among many that determine emotion and behavior.

ICD-10 describes reactive attachment disorder of childhood, known as RAD, and disinhibited attachment disorder, less well known as DAD. DSM-IV-TR also describes reactive attachment disorder of infancy or early childhood divided into two subtypes, inhibited type and disinhibited type, both known as RAD. The two classifications are similar and both include:

ICD-10 states in relation to the inhibited form only that the syndrome probably occurs as a direct result of severe parental neglect, abuse, or serious mishandling. DSM states in relation to both forms there must be a history of "pathogenic care" defined as persistent disregard of the child's basic emotional or physical needs or repeated changes in primary caregiver that prevents the formation of a discriminatory or selective attachment that is presumed to account for the disorder. For this reason, part of the diagnosis is the child's history of care rather than observation of symptoms.

In DSM-IV-TR the "inhibited" form is described as persistent failure to initiate or respond in a developmentally appropriate fashion to most social interactions, as manifest by excessively inhibited, hypervigilant, or highly ambivalent and contradictory responses (e.g., the child may respond to caregivers with a mixture of approach, avoidance, and resistance to comforting or may exhibit "frozen watchfulness", hypervigilance while keeping an impassive and still demeanour). Such infants do not seek or accept comfort at times of threat, alarm or distress, thus failing to maintain "proximity", an essential element of attachment behavior. The "disinhibited" form shows diffuse attachments as manifest by indiscriminate sociability with marked inability to exhibit appropriate selective attachments (e.g., excessive familiarity with relative strangers or lack of selectivity in choice of attachment figures). There is therefore a lack of "specificity" of attachment figure, the second basic element of attachment behavior.

The ICD-10 descriptions are comparable save that ICD-10 includes in its description several elements not included in DSM-IV-TR as follows:

The first of these is somewhat controversial, being a commission rather than omission and because abuse in and of itself does not lead to attachment disorder.

The inhibited form has a greater tendency to ameliorate with an appropriate caregiver, while the disinhibited form is more enduring. ICD-10 states the disinhibited form "tends to persist despite marked changes in environmental circumstances". Disinhibited and inhibited are not opposites in terms of attachment disorder and can coexist in the same child. The question of whether there are two subtypes has been raised. The World Health Organization acknowledges that there is uncertainty regarding the diagnostic criteria and the appropriate subdivision. One reviewer has commented on the difficulty of clarifying the core characteristics of and differences between atypical attachment styles and ways of categorizing more severe disorders of attachment.

, the American Psychiatric Association has proposed to redefine RAD into two distinct disorders in the DSM-V. Corresponding with the inhibited type, one disorder will be reclassified as "Reactive Attachment Disorder of Infancy and Early Childhood".

In regards to pathogenic care, or the type of care in which these behaviors are present, a new criterion for Disinhibited Social Engagement Disorder now includes chronically harsh punishment or other types of severely inept caregiving. Relating to pathogenic care for both proposed disorders, a new criterion is rearing in atypical environments such as institutions with high child/caregiver ratios that cut down on opportunities to form attachments with a caregiver.

The diagnostic complexities of RAD mean that careful diagnostic evaluation by a trained mental health expert with particular expertise in differential diagnosis is considered essential. Several other disorders, such as conduct disorders, oppositional defiant disorder, anxiety disorders, post traumatic stress disorder and social phobia share many symptoms and are often comorbid with or confused with RAD, leading to over and under diagnosis. RAD can also be confused with neuropsychiatric disorders such as autism, pervasive developmental disorder, childhood schizophrenia and some genetic syndromes. Infants with this disorder can be distinguished from those with organic illness by their rapid physical improvement after hospitalization. Autistic children are likely to be of normal size and weight and often exhibit a degree of intellectual disability. They are unlikely to improve upon being removed from the home.

In the absence of a standardized diagnosis system, many popular, informal classification systems or checklists, outside the DSM and ICD, were created out of clinical and parental experience within the field known as attachment therapy. These lists are unvalidated and critics state they are inaccurate, too broadly defined or applied by unqualified persons. Many are found on the websites of attachment therapists. Common elements of these lists such as lying, lack of remorse or conscience and cruelty do not form part of the diagnostic criteria under either DSM-IV-TR or ICD-10. Many children are being diagnosed with RAD because of behavioral problems that are outside the criteria. There is an emphasis within attachment therapy on aggressive behavior as a symptom of what they describe as attachment disorder whereas mainstream theorists view these behaviors as comorbid, externalizing behaviors requiring appropriate assessment and treatment rather than attachment disorders. However, knowledge of attachment relationships can contribute to the cause, maintenance and treatment of externalizing disorders.

The Randolph Attachment Disorder Questionnaire or RADQ is one of the better known of these checklists and is used by attachment therapists and others. The checklist includes 93 discrete behaviours, many of which either overlap with other disorders, like conduct disorder and oppositional defiant disorder, or are not related to attachment difficulties. Critics assert that it is unvalidated and lacks specificity.

Assessing the child's safety is an essential first step that determines whether future intervention can take place in the family unit or whether the child should be removed to a safe situation. Interventions may include psychosocial support services for the family unit (including financial or domestic aid, housing and social work support), psychotherapeutic interventions (including treating parents for mental illness, family therapy, individual therapy), education (including training in basic parenting skills and child development), and monitoring of the child's safety within the family environment

In 2005 the American Academy of Child and Adolescent Psychiatry laid down guidelines (devised by N.W. Boris and C.H. Zeanah) based on its published parameters for the diagnosis and treatment of RAD. Recommendations in the guidelines include the following:

Mainstream prevention programs and treatment approaches for attachment difficulties or disorders for infants and younger children are based on attachment theory and concentrate on increasing the responsiveness and sensitivity of the caregiver, or if that is not possible, placing the child with a different caregiver. These approaches are mostly in the process of being evaluated. The programs invariably include a detailed assessment of the attachment status or caregiving responses of the adult caregiver as attachment is a two-way process involving attachment behavior and caregiver response. Some of these treatment or prevention programs are specifically aimed at foster carers rather than parents, as the attachment behaviors of infants or children with attachment difficulties often do not elicit appropriate caregiver responses. Approaches include "Watch, wait and wonder," manipulation of sensitive responsiveness, modified "Interaction Guidance", "Clinician-Assisted Videofeedback Exposure Sessions (CAVES)", "Preschool Parent Psychotherapy", "Circle of Security", "Attachment and Biobehavioral Catch-up" (ABC), the New Orleans Intervention, and parent–child psychotherapy. Other treatment methods include Developmental, Individual-difference, and Relationship-based therapy (DIR, also referred to as Floor Time) by Stanley Greenspan, although DIR is primarily directed to treatment of pervasive developmental disorders.

The relevance of these approaches to intervention with fostered and adopted children with RAD or older children with significant histories of maltreatment is unclear.

The terms attachment disorder, attachment problems, and attachment therapy, although increasingly used, have no clear, specific, or consensus definitions. However, the terms and therapies often are applied to children who are maltreated, particularly those in the foster care, kinship care, or adoption systems, and related populations such as children adopted internationally from orphanages.

Outside the mainstream programs is a form of treatment generally known as attachment therapy, a subset of techniques (and accompanying novel diagnosis) for supposed attachment disorders including RAD. These "attachment disorders" use diagnostic criteria or symptom lists different to criteria under ICD-10 or DSM-IV-TR, or to attachment behaviors. Sufferers of "attachment disorder" are said to lack empathy and remorse.

Treatments of this pseudoscientific disorder are called "Attachment therapy". In general, these therapies are aimed at adopted or fostered children with a view to creating attachment in these children to their new caregivers. The theoretical base is broadly a combination of regression and catharsis, accompanied by parenting methods which emphasize obedience and parental control. There is considerable criticism of this form of treatment and diagnosis as it is largely unvalidated and has developed outside the scientific mainstream. There is little or no evidence base and techniques vary from non-coercive therapeutic work to more extreme forms of physical, confrontational and coercive techniques, of which the best known are holding therapy, rebirthing, rage-reduction and the Evergreen model. These forms of the therapy may well involve physical restraint, the deliberate provocation of rage and anger in the child by physical and verbal means including deep tissue massage, aversive tickling, enforced eye contact and verbal confrontation, and being pushed to revisit earlier trauma. Critics maintain that these therapies are not within the attachment paradigm, are potentially abusive, and are antithetical to attachment theory. The APSAC Taskforce Report of 2006 notes that many of these therapies concentrate on changing the child rather than the caregiver. Children may be described as "RADs", "Radkids" or "Radishes" and dire predictions may be made as to their supposedly violent futures if they are not treated with attachment therapy. The Mayo Clinic, a well known U.S. non-profit medical practice and medical research group, cautions against consulting with mental health providers who promote these types of methods and offer evidence to support their techniques; to date, this evidence base is not published within reputable medical or mental health journals.

The AACAP guidelines state that children with reactive attachment disorder are presumed to have grossly disturbed internal models for relating to others. However, the course of RAD is not well studied and there have been few efforts to examine symptom patterns over time. The few existing longitudinal studies (dealing with developmental change with age over a period of time) involve only children from poorly run Eastern European institutions.

Findings from the studies of children from Eastern European orphanages indicate that persistence of the inhibited pattern of RAD is rare in children adopted out of institutions into normative care-giving environments. However, there is a close association between duration of deprivation and severity of attachment disorder behaviors. The quality of attachments that these children form with subsequent care-givers may be compromised, but they probably no longer meet criteria for inhibited RAD. The same group of studies suggests that a minority of adopted, institutionalized children exhibit persistent indiscriminate sociability even after more normative caregiving environments are provided. Indiscriminate sociability may persist for years, even among children who subsequently exhibit preferred attachment to their new caregivers. Some exhibit hyperactivity and attention problems as well as difficulties in peer relationships. In the only longitudinal study that has followed children with indiscriminate behavior into adolescence, these children were significantly more likely to exhibit poor peer relationships.

Studies of children who were reared in institutions have suggested that they are inattentive and overactive, no matter what quality of care they received. In one investigation, some institution-reared boys were reported to be inattentive, overactive, and markedly unselective in their social relationships, while girls, foster-reared children, and some institution-reared children were not. It is not yet clear whether these behaviors should be considered as part of disordered attachment.

There is one case study on maltreated twins published in 1999 with a follow-up in 2006. This study assessed the twins between the ages of 19 and 36 months, during which time they suffered multiple moves and placements. The paper explores the similarities, differences and comorbidity of RAD, disorganized attachment and post traumatic stress disorder. The girl showed signs of the inhibited form of RAD while the boy showed signs of the indiscriminate form. It was noted that the diagnosis of RAD ameliorated with better care but symptoms of post traumatic stress disorder and signs of disorganized attachment came and went as the infants progressed through multiple placement changes. At age three, some lasting relationship disturbance was evident.

In the follow-up case study when the twins were aged three and eight years, the lack of longitudinal research on maltreated as opposed to institutionalized children was again highlighted. The girl's symptoms of disorganized attachment had developed into controlling behaviors—a well-documented outcome. The boy still exhibited self-endangering behaviors, not within RAD criteria but possibly within "secure base distortion", (where the child has a preferred familiar caregiver, but the relationship is such that the child cannot use the adult for safety while gradually exploring the environment). At age eight the children were assessed with a variety of measures including those designed to access representational systems, or the child's "internal working models". The twins' symptoms were indicative of different trajectories. The girl showed externalizing symptoms (particularly deceit), contradictory reports of current functioning, chaotic personal narratives, struggles with friendships, and emotional disengagement with her caregiver, resulting in a clinical picture described as "quite concerning". The boy still evidenced self-endangering behaviors as well as avoidance in relationships and emotional expression, separation anxiety and impulsivity and attention difficulties. It was apparent that life stressors had impacted each child differently. The narrative measures used were considered helpful in tracking how early attachment disruption is associated with later expectations about relationships.

One paper using questionnaires found that children aged three to six, diagnosed with RAD, scored lower on empathy but higher on self-monitoring (regulating your behavior to "look good"). These differences were especially pronounced based on ratings by parents, and suggested that children with RAD may systematically report their personality traits in overly positive ways. Their scores also indicated considerably more behavioral problems than scores of the control children.

Epidemiological data are limited, but reactive attachment disorder appears to be very uncommon. The prevalence of RAD is unclear but it is probably quite rare, other than in populations of children being reared in the most extreme, deprived settings such as some orphanages. There is little systematically gathered epidemiologic information on RAD. A cohort study of 211 Copenhagen children to the age of 18 months found a prevalence of 0.9%.

Attachment disorders tend to occur in a definable set of contexts such as within some types of institutions, in the presence of repeated changes of primary caregiver or of extremely neglectful identifiable primary caregivers who show persistent disregard for the child's basic attachment needs, but not all children raised in these conditions develop an attachment disorder. Studies undertaken on children from Eastern European orphanages from the mid-1990s showed significantly higher levels of both forms of RAD and of insecure patterns of attachment in the institutionalized children, regardless of how long they had been there. It would appear that children in institutions like these are unable to form selective attachments to their caregivers. The difference between the institutionalized children and the control group had lessened in the follow-up study three years later, although the institutionalized children continued to show significantly higher levels of indiscriminate friendliness. However, even among children raised in the most deprived institutional conditions the majority did not show symptoms of this disorder.

A 2002 study of children in residential nurseries in Bucharest, in which the DAI was used, challenged the current DSM and ICD conceptualizations of disordered attachment and showed that inhibited and disinhibited disorders could coexist in the same child.

There are two studies on the incidence of RAD relating to high risk and maltreated children in the U.S. Both used ICD, DSM and the DAI. The first, in 2004, reported that children from the maltreatment sample were significantly more likely to meet criteria for one or more attachment disorders than children from the other groups, however this was mainly the proposed new classification of disrupted attachment disorder rather than the DSM or ICD classified RAD or DAD. The second study, also in 2004, attempted to ascertain the prevalence of RAD and whether it could be reliably identified in "maltreated" rather than "neglected" toddlers. Of the 94 maltreated toddlers in foster care, 35% were identified as having ICD RAD and 22% as having ICD DAD, and 38% fulfilled the DSM criteria for RAD. This study found that RAD could be reliably identified and also that the inhibited and disinhibited forms were not independent. However, there are some methodological concerns with this study. A number of the children identified as fulfilling the criteria for RAD did in fact have a preferred attachment figure.

It has been suggested by some within the field of attachment therapy that RAD may be quite prevalent because severe child maltreatment, which is known to increase risk for RAD, is prevalent and because children who are severely abused may exhibit behaviors similar to RAD behaviors. The APSAC Taskforce consider this inference to be flawed and questionable. Severely abused children may exhibit similar behaviors to RAD behaviors but there are several far more common and demonstrably treatable diagnoses which may better account for these difficulties. Further, many children experience severe maltreatment and do not develop clinical disorders. Resilience is a common and normal human characteristic. RAD does not underlie all or even most of the behavioral and emotional problems seen in foster children, adoptive children, or children who are maltreated and rates of child abuse and/or neglect or problem behaviors are not a benchmark for estimates of RAD.

There are few data on comorbid conditions, but there are some conditions that arise in the same circumstances in which RAD arises, such as institutionalization or maltreatment. These are principally developmental delays and language disorders associated with neglect. Conduct disorders, oppositional defiant disorder, anxiety disorders, post-traumatic stress disorder and social phobia share many symptoms and are often comorbid with or confused with RAD. Attachment disorder behaviors amongst institutionalized children are correlated with attentional and conduct problems and cognitive levels but nonetheless appear to index a distinct set of symptoms and behaviors.

Reactive attachment disorder first made its appearance in standard nosologies of psychological disorders in DSM-III, 1980, following an accumulation of evidence on institutionalized children. The criteria included a requirement of onset before the age of 8 months and was equated with failure to thrive. Both these features were dropped in DSM-III-R, 1987. Instead, onset was changed to being within the first 5 years of life and the disorder itself was divided into two subcategories, inhibited and disinhibited. These changes resulted from further research on maltreated and institutionalized children and remain in the current version, DSM-IV, 1994, and its 2000 text revision, DSM-IV-TR, as well as in ICD-10, 1992. Both nosologies focus on young children who are not merely at increased risk for subsequent disorders but are already exhibiting clinical disturbance.

The pathological absence of a discriminatory or selective attachment needs to be differentiated from the existence of attachments with either typical or somewhat atypical behavior patterns, known as "styles" or "patterns". There are four attachment styles ascertained and used within developmental attachment research. These are known as "secure", "anxious-ambivalent", "anxious-avoidant", (all "organized") and "disorganized". The latter three are characterised as "insecure". These are assessed using the Strange Situation Procedure, designed to assess the quality of attachments rather than whether an attachment exists at all.

A securely attached toddler will explore freely while the caregiver is present, engage with strangers, be visibly upset when the caregiver departs, and happy to see the caregiver return. The anxious-ambivalent toddler is anxious of exploration, extremely distressed when the caregiver departs but ambivalent when the caregiver returns. The anxious-avoidant toddler will not explore much, avoid or ignore the parent—showing little emotion when the parent departs or returns—and treat strangers much the same as caregivers with little emotional range shown. The disorganized/disoriented toddler shows a lack of a coherent style or pattern for coping. Evidence suggests this occurs when the caregiving figure is also an object of fear, thus putting the child in an irresolvable situation regarding approach and avoidance. On reunion with the caregiver, these children can look dazed or frightened, freezing in place, backing toward the caregiver or approaching with head sharply averted, or showing other behaviors implying fear of the person who is being sought. It is thought to represent a breakdown of an inchoate attachment strategy and it appears to affect the capacity to regulate emotions.

Although there are a wide range of attachment difficulties within the styles which may result in emotional disturbance and increase the risk of later psychopathologies, particularly the disorganized style, none of the styles constitute a disorder in themselves and none equate to criteria for RAD as such. A disorder in the clinical sense is a condition requiring treatment, as opposed to risk factors for subsequent disorders. Reactive attachment disorder denotes a lack of typical attachment behaviors rather than an attachment style, however problematic that style may be, in that there is an unusual lack of discrimination between familiar and unfamiliar people in both forms of the disorder. Such discrimination does exist as a feature of the social behavior of children with atypical attachment styles. Both DSM-IV and ICD-10 depict the disorder in terms of socially aberrant behavior in general rather than focusing more specifically on attachment behaviors as such. DSM-IV emphasizes a failure to initiate or respond to social interactions across a range of relationships and ICD-10 similarly focuses on contradictory or ambivalent social responses that extend across social situations. The relationship between patterns of attachment in the Strange Situation and RAD is not yet clear.

There is a lack of consensus about the precise meaning of the term "attachment disorder". The term is frequently used both as an alternative to reactive attachment disorder and in discussions about different proposed classifications for disorders of attachment beyond the limitations of the ICD and DSM classifications. It is also used within the field of attachment therapy, as is the term reactive attachment disorder, to describe a range of problematic behaviors not within the ICD or DSM criteria or not related directly to attachment styles or difficulties at all.

Research from the late 1990s indicated there were disorders of attachment not captured by DSM or ICD and showed that RAD could be diagnosed reliably without evidence of pathogenic care, thus illustrating some of the conceptual difficulties with the rigid structure of the current definition of RAD. Research published in 2004 showed that the disinhibited form can endure alongside structured attachment behavior (of any style) towards the child's permanent caregivers.

Some authors have proposed a broader continuum of definitions of attachment disorders ranging from RAD through various attachment difficulties to the more problematic attachment styles. There is as yet no consensus, on this issue but a new set of practice parameters containing three categories of attachment disorder has been proposed by C.H. Zeanah and N. Boris. The first of these is "disorder of attachment," in which a young child has no preferred adult caregiver. The proposed category of disordered attachment is parallel to RAD in its inhibited and disinhibited forms, as defined in DSM and ICD. The second category is "secure base distortion", where the child has a preferred familiar caregiver, but the relationship is such that the child cannot use the adult for safety while gradually exploring the environment. Such children may endanger themselves, cling to the adult, be excessively compliant, or show role reversals in which they care for or punish the adult. The third type is "disrupted attachment". Disrupted attachment is not covered under ICD-10 and DSM criteria, and results from an abrupt separation or loss of a familiar caregiver to whom attachment has developed. This form of categorisation may demonstrate more clinical accuracy overall than the current DSM-IV-TR classification, but further research is required. The practice parameters would also provide the framework for a diagnostic protocol. Most recently, Daniel Schechter and Erica Willheim have shown a relationship between some maternal violence-related posttraumatic stress disorder and secure base distortion (see above) which is characterized by child recklessness, separation anxiety, hypervigilance, and role-reversal.

Some research indicates there may be a significant overlap between behaviors of the inhibited form of RAD or DAD and aspects of disorganized attachment where there is an identified attachment figure.

An ongoing question is whether RAD should be thought of as a disorder of the child's personality or a distortion of the relationship between the child and a specific other person. It has been noted that as attachment disorders are by their very nature relational disorders, they do not fit comfortably into nosologies that characterize the disorder as centered on the person. Work by C.H. Zeanah indicates that atypical attachment-related behaviors may occur with one caregiver but not with another. This is similar to the situation reported for attachment styles, in which a particular parent's frightened expression has been considered as possibly responsible for disorganized/disoriented reunion behavior during the Strange Situation Procedure.

The draft of the proposed DSM-V suggests dividing RAD into two disorders, Reactive Attachment Disorder for the current inhibited form of RAD, and Disinhibited Social Engagement Disorder for what is currently the disinhibited form of RAD, with some alterations in the proposed DSM definition.

Attachment theory, originating in the work of John Bowlby and developed by Mary Ainsworth, is a psychological, evolutionary and ethological theory that provides a descriptive and explanatory framework for understanding interpersonal relationships between human beings. Bowlby's observations of close attachments led him to believe that close emotional bonds or “attachments” between an infant and their primary caregiver is an important requirement that is necessary to form “normal social and emotional development”.

Child development

Child development entails the biological, psychological and emotional changes that occur in human beings between birth and the conclusion of adolescence, as the individual progresses from dependency to increasing autonomy. It is a continuous process with a predictable sequence, yet having a unique course for every child. It does not progress at the same rate and each stage is affected by the preceding developmental experiences. Because these developmental changes may be strongly influenced by genetic factors and events during prenatal life, genetics and prenatal development are usually included as part of the study of child development. Related terms include developmental psychology, referring to development throughout the lifespan, and pediatrics, the branch of medicine relating to the care of children. Developmental change may occur as a result of genetically-controlled processes known as maturation, or as a result of environmental factors and learning, but most commonly involves an interaction between the two. It may also occur as a result of human nature and our ability to learn from our environment.

There are various definitions of periods in a child's development, since each period is a continuum with individual differences regarding start and ending. Some age-related development periods and examples of defined intervals are: newborn (ages 0–4 weeks); infant (ages 4 weeks – 1 year); toddler (ages 1–3 years); preschooler (ages 4–6 years); school-aged child (ages 6–11 years); adolescent (ages 12–19).

Promoting child development through parental training, among other factors, promotes excellent rates of child development.
Parents play a large role in a child's life, socialization, and development. Having multiple parents can add stability to the child's life and therefore encourage healthy development. Another influential factor in a child's development is the quality of their care. Child care programs present a critical opportunity for the promotion of child development.

The optimal development of children is considered vital to society and so it is important to understand the social, cognitive, emotional, and educational development of children. Increased research and interest in this field has resulted in new theories and strategies, with specific regard to practice that promotes development within the school system. There are also some theories that seek to describe a sequence of states that compose child development.

Also called "development in context" or "human ecology" theory, ecological systems theory, originally formulated by Urie Bronfenbrenner specifies four types of nested environmental systems, with bi-directional influences within and between the systems. The four systems are microsystem, mesosystem, exosystem, and macrosystem. Each system contains roles, norms and rules that can powerfully shape development. Since its publication in 1979, Bronfenbrenner's major statement of this theory, "The Ecology of Human Development" has had widespread influence on the way psychologists and others approach the study of human beings and their environments. As a result of this influential conceptualization of development, these environments — from the family to economic and political structures — have come to be viewed as part of the life course from childhood through adulthood.

Jean Piaget was a Swiss scholar who began his studies in intellectual development in the 1920s. Piaget's first interests were those that dealt with the ways in which animals adapt to their environments and his first scientific article about this subject was published when he was 10 years old. This eventually led him to pursue a Ph.D. in Zoology, which then led him to his second interest in epistemology. Epistemology branches off from philosophy and deals with the origin of knowledge. Piaget believed the origin of knowledge came from Psychology, so he traveled to Paris and began working on the first “standardized intelligence test” at Alfred Binet laboratories; this influenced his career greatly. As he carried out this intelligence testing he began developing a profound interest in the way children's intellectualism works. As a result, he developed his own laboratory and spent years recording children's intellectual growth and attempted to find out how children develop through various stages of thinking. This led to Piaget develop four important stages of cognitive development: sensorimotor stage (birth to age 2), preoperational stage (age 2 to 7), concrete-operational stage (ages 7 to 12), and formal-operational stage (ages 11 to 12, and thereafter). Piaget concluded that adaption to an environment (behaviour) is managed through schemes and adaption occurs through "assimilation" and "accommodation".

Sensorimotor: (birth to about age 2)

This is the first stage in Piaget's theory, where infants have the following basic senses: vision, hearing, and motor skills. In this stage, knowledge of the world is limited but is constantly developing due to the child's experiences and interactions. According to Piaget, when an infant reaches about 7–9 months of age they begin to develop what he called object permanence, this means the child now has the ability to understand that objects keep existing even when they cannot be seen. An example of this would be hiding the child's favorite toy under a blanket, although the child cannot physically see it they still know to look under the blanket.

Preoperational: (begins about the time the child starts to talk, about age 2)

During this stage of development, young children begin analyzing their environment using mental symbols. These symbols often include words and images and the child will begin to apply these various symbols in their everyday lives as they come across different objects, events, and situations. However, Piaget's main focus on this stage and the reason why he named it “preoperational” is because children at this point are not able to apply specific cognitive operations, such as mental math. In addition to symbolism, children start to engage in pretend play in which they pretend to be people they are not (teachers, superheroes). In addition, they sometimes use different props to make this pretend play more real. Some deficiencies in this stage of development are that children who are about 3–4 years old often display what is called egocentrism, which means the child is not able to see someone else's point of view, they feel as if every other person is experiencing the same events and feelings that they are experiencing. However, at about 7, thought processes of children are no longer egocentric and are more intuitive, meaning they now think about the way something looks instead of rational thinking.

Concrete: (about first grade to early adolescence)

During this stage, children between the age of 7 and 11 use appropriate logic to develop cognitive operations and begin applying this new thinking to different events they may encounter. Children in this stage incorporate inductive reasoning, which involves drawing conclusions from other observations in order to make a generalization. Unlike the preoperational stage, children can now change and rearrange mental images and symbols to form a logical thought, an example of this is reversibility in which the child now has the ability to reverse an action just by doing the opposite.

Formal operations: (about early adolescence to mid/late adolescence)

The final stage of Piaget's cognitive development defines a child as now having the ability to “think more rationally and systematically about abstract concepts and hypothetical events”. Some positive aspects during this time is that child or adolescent begins forming their identity and begin understanding why people behave the way they behave. However, there are also some negative aspects which include the child or adolescent developing some egocentric thoughts which include the imaginary audience and the personal fable. An imaginary audience is when an adolescent feels that the world is just as concerned and judgemental of anything the adolescent does as they are; an adolescent may feel as if they are “on stage” and everyone is a critic and they are the ones being critiqued. A personal fable is when the adolescent feels that he or she is a unique person and everything they do is unique. They feel as if they are the only ones that have ever experienced what they are experiencing and that they are invincible and nothing bad will happen to them, it will only happen to others.

Vygotsky was a Russian theorist, who proposed the sociocultural theory. During the 1920s–1930s while Piaget was developing his own theory, Vygotsky was an active scholar and at that time his theory was said to be “recent” because it was translated out of Russian language and began influencing Western thinking. He posited that children learn through hands-on experience, as Piaget suggested. However, unlike Piaget, he claimed that timely and sensitive intervention by adults when a child is on the edge of learning a new task (called the zone of proximal development) could help children learn new tasks. This technique is called "scaffolding," because it builds upon knowledge children already have with new knowledge that adults can help the child learn. An example of this might be when a parent "helps" an infant clap or roll her hands to the pat-a-cake rhyme, until she can clap and roll her hands herself.

Vygotsky was strongly focused on the role of culture in determining the child's pattern of development. He argued that "Every function in the child's cultural development appears twice: first, on the social level, and later, on the individual level; first, between people (interpsychological) and then inside the child (intrapsychological). This applies equally to voluntary attention, to logical memory, and to the formation of concepts. All the higher functions originate as actual relationships between individuals."

Vygotsky felt that development was a process and saw periods of crisis in child development during which there was a qualitative transformation in the child's mental functioning.

Attachment theory, originating in the work of John Bowlby and developed by Mary Ainsworth, is a psychological, evolutionary and ethological theory that provides a descriptive and explanatory framework for understanding interpersonal relationships between human beings. Bowlby's observations of close attachments led him to believe that close emotional bonds or “attachments” between an infant and their primary caregiver is an important requirement that is necessary to form “normal social and emotional development”.

Erikson, a follower of Freud's, synthesized both Freud's and his own theories to create what is known as the "psychosocial" stages of human development, which span from birth to death, and focuses on "tasks" at each stage that must be accomplished to successfully navigate life's challenges.

Erikson's eight stages consist of the following:

John B. Watson’s behaviorism theory forms the foundation of the behavioral model of development 1925. Watson was able to explain the aspects of human psychology through the process of classical conditioning. With this process, Watson believed that all individual differences in behavior were due to different learning experiences. He wrote extensively on child development and conducted research (see Little Albert experiment). This experiment had shown that phobia could be created by classical conditioning. Watson was instrumental in the modification of William James’ stream of consciousness approach to construct a stream of behavior theory. Watson also helped bring a natural science perspective to child psychology by introducing objective research methods based on observable and measurable behavior. Following Watson's lead, B.F. Skinner further extended this model to cover operant conditioning and verbal behavior. Skinner used the operant chamber, or Skinner box, to observe the behavior of small organisms in a controlled situation and proved that organisms' behaviors are influenced by the environment. Furthermore, he used reinforcement and punishment to shape in desired behavior.

In accordance with his view that the sexual drive is a basic human motivation, Sigmund Freud developed a psychosexual theory of human development from infancy onward, divided into five stages. Each stage centered around the gratification of the libido within a particular area, or erogenous zone, of the body. He also argued that as humans develop, they become fixated on different and specific objects through their stages of development. Each stage contains conflict which requires resolution to enable the child to develop.

The use of dynamical systems theory as a framework for the consideration of development began in the early 1990s and has continued into the present century. Dynamic systems theory stresses nonlinear connections (e.g., between earlier and later social assertiveness) and the capacity of a system to reorganize as a phase shift that is stage-like in nature. Another useful concept for developmentalists is the attractor state, a condition (such as teething or stranger anxiety) that helps to determine apparently unrelated behaviors as well as related ones. Dynamic systems theory has been applied extensively to the study of motor development; the theory also has strong associations with some of Bowlby's views about attachment systems. Dynamic systems theory also relates to the concept of the transactional process, a mutually interactive process in which children and parents simultaneously influence each other, producing developmental change in both over time.

The "core knowledge perspective" is an evolutionary theory in child development that proposes "infants begin life with innate, special-purpose knowledge systems referred to as core domains of thought" There are five core domains of thought, each of which is crucial for survival, which simultaneously prepare us to develop key aspects of early cognition; they are: physical, numerical, linguistic, psychological, and biological.

Although the identification of developmental milestones is of interest to researchers and to children's caregivers, many aspects of developmental change are continuous and do not display noticeable milestones of change. Continuous developmental changes, like growth in stature, involve fairly gradual and predictable progress toward adult characteristics. When developmental change is discontinuous, however, researchers may identify not only milestones of development, but related age periods often called stages. A stage is a period of time, often associated with a known chronological age range, during which a behavior or physical characteristic is qualitatively different from what it is at other ages. When an age period is referred to as a stage, the term implies not only this qualitative difference, but also a predictable sequence of developmental events, such that each stage is both preceded and followed by specific other periods associated with characteristic behavioral or physical qualities.

Stages of development may overlap or be associated with specific other aspects of development, such as speech or movement. Even within a particular developmental area, transition into a stage may not mean that the previous stage is completely finished. For example, in Erikson's discussion of stages of personality, this theorist suggests that a lifetime is spent in reworking issues that were originally characteristic of a childhood stage. Similarly, the theorist of cognitive development, Piaget, described situations in which children could solve one type of problem using mature thinking skills, but could not accomplish this for less familiar problems, a phenomenon he called horizontal decalage.

Although developmental change runs parallel with chronological age, age itself cannot cause development. The basic mechanisms or causes of developmental change are genetic factors and environmental factors. Genetic factors are responsible for cellular changes like overall growth, changes in proportion of body and brain parts, and the maturation of aspects of function such as vision and dietary needs. Because genes can be "turned off" and "turned on", the individual's initial genotype may change in function over time, giving rise to further developmental change. Environmental factors affecting development may include both diet and disease exposure, as well as social, emotional, and cognitive experiences. However, examination of environmental factors also shows that young human beings can survive within a fairly broad range of environmental experiences.

Rather than acting as independent mechanisms, genetic and environmental factors often interact to cause developmental change. Some aspects of child development are notable for their plasticity, or the extent to which the direction of development is guided by environmental factors as well as initiated by genetic factors. When an aspect of development is strongly affected by early experience, it is said to show a high degree of plasticity; when the genetic make-up is the primary cause of development, plasticity is said to be low. Plasticity may involve guidance by endogenous factors like hormones as well as by exogenous factors like infection.

One kind of environmental guidance of development has been described as experience-dependent plasticity, in which behavior is altered as a result of learning from the environment. Plasticity of this type can occur throughout the lifespan and may involve many kinds of behavior, including some emotional reactions. A second type of plasticity, experience-expectant plasticity, involves the strong effect of specific experiences during limited sensitive periods of development. For example, the coordinated use of the two eyes, and the experience of a single three-dimensional image rather than the two-dimensional images created by light in each eye, depend on experiences with vision during the second half of the first year of life. Experience-expectant plasticity works to fine-tune aspects of development that cannot proceed to optimum outcomes as a result of genetic factors working alone.

In addition to the existence of plasticity in some aspects of development, genetic-environmental correlations may function in several ways to determine the mature characteristics of the individual. Genetic-environmental correlations are circumstances in which genetic factors make certain experiences more likely to occur. For example, in passive genetic-environmental correlation, a child is likely to experience a particular environment because his or her parents' genetic make-up makes them likely to choose or create such an environment. In evocative genetic-environmental correlation, the child's genetically-caused characteristics cause other people to respond in certain ways, providing a different environment than might occur for a genetically-different child; for instance, a child with Down syndrome may be treated more protectively and less challengingly than a non-Down child. Finally, an active genetic-environmental correlation is one in which the child chooses experiences that in turn have their effect; for instance, a muscular, active child may choose after-school sports experiences that create increased athletic skills, but perhaps preclude music lessons. In all of these cases, it becomes difficult to know whether child characteristics were shaped by genetic factors, by experiences, or by a combination of the two.Empirical research that attempts to answer these questions may follow a number of patterns. Initially, observational research in naturalistic conditions may be needed to develop a narrative describing and defining an aspect of developmental change, such as changes in reflex reactions in the first year. This type of work may be followed by correlational studies, collecting information about chronological age and some type of development such as vocabulary growth; correlational statistics can be used to state change. Such studies examine the characteristics of children at different ages. These methods may involve longitudinal studies, in which a group of children are re-examined on a number of occasions as they get older, or cross-sectional studies, in which groups of children of different ages are tested once and compared with each other, or there may be a combination of these approaches. Some child development studies examine the effects of experience or heredity by comparing characteristics of different groups of children in a necessarily non-randomized design. Other studies can use randomized designs to compare outcomes for groups of children who receive different interventions or educational treatments.

Milestones are changes in specific physical and mental abilities (such as walking and understanding language) that mark the end of one developmental period and the beginning of another. For stage theories, milestones indicate a stage transition. Studies of the accomplishment of many developmental tasks have established typical chronological ages associated with developmental milestones. However, there is considerable variation in the achievement of milestones, even between children with developmental trajectories within the typical range. Some milestones are more variable than others; for example, receptive speech indicators do not show much variation among children with typical hearing, but expressive speech milestones can be quite variable.

A common concern in child development is developmental delay involving a delay in an age-specific ability for important developmental milestones. Prevention of and early intervention in developmental delay are significant topics in the study of child development. Developmental delays should be diagnosed by comparison with characteristic variability of a milestone, not with respect to average age at achievement. An example of a milestone would be eye-hand coordination, which includes a child's increasing ability to manipulate objects in a coordinated manner. Increased knowledge of age-specific milestones allows parents and others to keep track of appropriate development.

There is a phenomenal growth or exponential increase of child development from the age of 4 to 15 years old especially during the age of 4 to 7 years old based on the Yamana chart ). The Heckman's chart shows that the highest return of investment in education is maximum during the early years (age 1 to 3 years old) and decreases to a plateau during the school-aged years and adolescence. There are various child development tables or charts e.g. the PILES table where PILES stands for Physical, Intellectual, Language, Emotional and Social development aspects.

Child development is not a matter of a single topic, but progresses somewhat differently for different aspects of the individual. Here are descriptions of the development of a number of physical and mental characteristics.

Physical growth in stature and weight occurs over the 15–20 years following birth, as the individual changes from the average weight of 3.5 kg and length of 50 cm at full term birth to full adult size. As stature and weight increase, the individual's proportions also change, from the relatively large head and small torso and limbs of the neonate, to the adult's relatively small head and long torso and limbs. The child's pattern of growth is in a head-to-toe direction, or cephalocaudal, and in an inward to outward pattern (center of the body to the peripheral) called proximodistal.

The speed of physical growth is rapid in the months after birth, then slows, so birth weight is doubled in the first four months, tripled by age 12 months, but not quadrupled until 24 months. Growth then proceeds at a slow rate until shortly before puberty (between
about 9 and 15 years of age), when a period of rapid growth occurs.
Growth is not uniform in rate and timing across all body parts. At birth, head size is already relatively near to that of an adult, but the lower parts of the body are much smaller than adult size. In the course of development, then, the head grows relatively little, and torso and limbs undergo a great deal of growth.

Genetic factors play a major role in determining the growth rate, and particularly the changes in proportion characteristic of early human development. However, genetic factors can produce the maximum growth only if environmental conditions are adequate. Poor nutrition and frequent injury and disease can reduce the individual's adult stature, but the best environment cannot cause growth to a greater stature than is determined by heredity.

Individual differences in height and weight during childhood are considerable. Some of these differences are due to family genetic factors, others to environmental factors, but at some points in development they may be strongly influenced by individual differences in reproductive maturation.

The American Association of Clinical Endocrinologists defines short stature as height more than 2 standard deviations below the mean for age and gender, which corresponds to the shortest 2.3% of individuals. In contrast, failure to thrive is usually defined in terms of weight, and can be evaluated either by a low weight for the child's age, or by a low rate of increase in the weight. A similar term, stunted growth, generally refers to reduced growth rate as a manifestation of malnutrition in early childhood.

Abilities for physical movement change through childhood from the largely reflexive (unlearned, involuntary) movement patterns of the young infant to the highly skilled voluntary movements characteristic of later childhood and adolescence.

"Motor learning refers to the increasing spatial and temporal accuracy of movements with practice".
Motor skills can be divided into two categories: first as basic skills necessary for everyday life and secondly, as recreational skills such as skills for employment or certain specialties based on interest.

The speed of motor development is rapid in early life, as many of the reflexes of the newborn alter or disappear within the first year, and slows later. Like physical growth, motor development shows predictable patterns of cephalocaudal (head to foot) and proximodistal (torso to extremities) development, with movements at the head and in the more central areas coming under control before those of the lower part of the body or the hands and feet. Types of movement develop in stage-like sequences; for example, locomotion at 6–8 months involves creeping on all fours, then proceeds to pulling to stand, "cruising" while holding on to an object, walking while holding an adult's hand, and finally walking independently. Older children continue the sequence by walking sideways or backward, galloping, hopping, skipping with one foot and walking with the other, and finally skipping. By middle childhood and adolescence, new motor skills are acquired by instruction or observation rather than in a predictable sequence. There are executive functions of the brain (working memory, timing measure of inhibition and switching) which are important to motor skills. Critiques to the order of Executive Functioning leads to Motor Skills, suggesting Motor Skills can support Executive Functioning in the brain.

The mechanisms involved in motor development involve some genetic components that determine the physical size of body parts at a given age, as well as aspects of muscle and bone strength. The main areas of the brain involved in motor skills are the frontal cortex, parietal cortex and basal ganglia. The dorsolateral frontal cortex is responsible for strategic processing. The parietal cortex is important in controlling perceptual-motor integration and the basal ganglia and supplementary motor cortex are responsible for motor sequences.

According to a study showing the different relationships between limbs of the body and coordination in infants, genetic components have a huge impact on motor development( Piek, Gasson, Barrett, & Case (2002)). Intra-limb correlations, like the strong relationship and distance between hip and knee joints, were studied and proved to affect the way an infant will walk. There are also bigger genetic factors like the tendency to use the left or right side of the body more, predicting the dominant hand early. Sample t-tests proved that there was a significant difference between both sides at 18 weeks for girls and the right side was considered to be more dominant( Piek et al. (2002)). Some factors, like the fact that boys tend to have larger and longer arms are biological constraints that we cannot control, yet have an influence for example, on when an infant will reach
sufficiently. Overall, there are sociological factors and genetic factors that influence motor development.
Nutrition and exercise also determine strength and therefore the ease and accuracy with which a body part can be moved. Flexibility is also affected by nutrition and exercise as well. It has also been shown that the frontal lobe develops posterio-anteriorally (from back to front). This is significant in motor development because the hind portion of the frontal lobe is known to control motor functions. This form of development is known as "Portional Development" and explains why motor functions develop relatively quickly during typical childhood development, while logic, which is controlled by the middle and front portions of the frontal lobe, usually will not develop until late childhood and early adolescence. Opportunities to carry out movements help establish the abilities to flex (move toward the trunk) and extend body parts, both capacities are necessary for good motor ability. Skilled voluntary movements such as passing objects from hand to hand develop as a result of practice and learning. Mastery Climate is a suggested successful learning environment for children to promote motor skills by their own motivation. This promotes participation and active learning in children, which according to Piaget's theory of cognitive development is extremely important in early childhood rule.

Typical individual differences in motor ability are common and depend in part on the child's weight and build. Infants with smaller, slimmer, and more maturely proportionated infants tended to belly crawl and crawl earlier than the infants with larger builds. Infants with more motor experience have been shown to belly crawl and crawl sooner. Not all infants go through the stages of belly crawling. However, those who skip the stage of belly crawling are not as proficient in their ability to crawl on their hands and knees. After the infant period, typical individual differences are strongly affected by opportunities to practice, observe, and be instructed on specific movements. Atypical motor development such as persistent primitive reflexis beyond 4–6 months or delayed walking may be an indication of developmental delays or conditions such as autism, cerebral palsy, or down syndrome. Lower motor coordination results in difficulties with speed accuracy and trade-off in complex tasks.

Children with Down syndrome or Developmental coordination disorder are late to reach major motor skills milestones. A few examples of these milestones are sucking, grasping, rolling, sitting up and walking, talking. Children with Down syndrome sometimes have heart problems, frequent ear infections, hypotonia, or undeveloped muscle mass. This syndrome is caused by atypical chromosomal development. Along with Down syndrome, children can also be diagnosed with a learning disability. Learning Disabilities include disabilities in any of the areas related to language, reading, and mathematics. Basic reading skills is the most common learning disability in children, which, like other disabilities, focuses on the difference between a child's academic achievement and his or her apparent capacity to learn.

Regardless of the culture a baby is born into, they are born with a few core domains of knowledge. These principals allow him or her to make sense of their environment and learn upon previous experience by using motor skills such as grasping or crawling. There are some population differences in motor development, with girls showing some advantages in small muscle usage, including articulation of sounds with lips and tongue. Ethnic differences in reflex movements of newborn infants have been reported, suggesting that some biological factor is at work. Cultural differences may encourage learning of motor skills like using the left hand only for sanitary purposes and the right hand for all other uses, producing a population difference. Cultural factors are also seen at work in practiced voluntary movements such as the use of the foot to dribble a soccer ball or the hand to dribble a basketball.

Cognitive development is primarily concerned with ways in which young children acquire, develop, and use internal mental capabilities such as problem solving, memory, and language.

The capacity to learn, remember, and symbolise information, and to solve problems, exists at a simple level in young infants, who can perform cognitive tasks such as discriminating animate and inanimate beings or recognizing small numbers of objects. During childhood, learning and information-processing increase in speed, memory becomes increasingly longer, and symbol use and the capacity for abstraction develop, until a near-adult level is reached by adolescence.

Cognitive development has genetic and other biological mechanisms, as is seen in the many genetic causes of intellectual disability. Environmental factors including food and nutrition, responsiveness of parents, daily experiences, physical activity and love can influence early brain development of children. However, although it is assumed that brain functions cause cognitive events, it has not been possible to measure specific brain changes and show that they cause cognitive change. Developmental advances in cognition are also related to experience and learning, and this is particularly the case for higher-level abilities like abstraction, which depend to a considerable extent on formal education.

The ability to learn temporal patterns in sequenced actions was investigated in elementary-school age children. Temporal learning depends upon a process of integrating timing patterns with action sequences. Children ages 6–13 and young adults performed a serial response time task in which a response and a timing sequence were presented repeatedly in a phase-matched manner, allowing for integrative learning. The degree of integrative learning was measured as the slowing in performance that resulted when phase-shifting the sequences. Learning was similar for the children and adults on average but increased with age for the children. Executive function measured by Wisconsin Card Sorting Test (WCST) performance as well as a measure of response speed also improved with age. Finally, WCST performance and response speed predicted temporal learning. Taken together, the results indicate that temporal learning continues to develop in pre-adolescents and that maturing executive function or processing speed may play an important role in acquiring temporal patterns in sequenced actions and the development of this ability.

There are typical individual differences in the ages at which specific cognitive abilities are achieved, but schooling for children in industrialized countries is based on the assumption that these differences are not large. Atypical delays in cognitive development are problematic for children in cultures that demand advanced cognitive skills for work and for independent living.

There are few population differences in cognitive development. Boys and girls show some differences in their skills and preferences, but there is a great deal of overlap between the groups. Differences in cognitive achievement of different ethnic groups appears to result from cultural or other environmental factors.

Newborn infants do not seem to experience fear or have preferences for contact with any specific people. In the first few months they only experience happiness, sadness, and anger. A baby's first smile usually occurs between 6 and 10 weeks. It is called a ‘social smile’ because it usually occurs during social interactions. By about 8–12 months, they go through a fairly rapid change and become fearful of perceived threats; they also begin to prefer familiar people and show anxiety and distress when separated from them or approached by strangers.

Separation anxiety is a typical stage of development to an extent. Kicking, screaming, and throwing temper tantrums are perfectly typical symptoms for separation anxiety. Depending on the level of intensity, one may determine whether or not a child has separation anxiety disorder. This is when a child constantly refuses to separate from the parent, but in an intense manner. This can be given special treatment but the parent usually cannot do anything about the situation.

The capacity for empathy and the understanding of social rules begin in the preschool period and continue to develop into adulthood. Middle childhood is characterized by friendships with age-mates, and adolescence by emotions connected with sexuality and the beginnings of romantic love. Anger seems most intense during the toddler and early preschool period and during adolescence.

Some aspects of social-emotional development, like empathy, develop gradually, but others, like fearfulness, seem to involve a rather sudden reorganization of the child's experience of emotion. Sexual and romantic emotions develop in connection with physical maturation.

Genetic factors appear to regulate some social-emotional developments that occur at predictable ages, such as fearfulness, and attachment to familiar people. Experience plays a role in determining which people are familiar, which social rules are obeyed, and how anger is expressed.

Parenting practices have been shown to predict children's emotional intelligence. The objective is to study the time mothers and children spent together in joint activity, the types of activities that they develop when they are together, and the relation that those activities have with the children's trait emotional intelligence. Data was collected for both mothers and children (N = 159) using self-report questionnaires. Correlations between time variables and trait emotional intelligence dimensions were computed using Pearson's Product-Moment Correlation Coefficient. Partial correlations between the same variables controlling for responsive parenting were also computed. The amount of time mothers spent with their children and the quality of their interactions are important in terms of children's trait emotional intelligence, not only because those times of joint activity reflect a more positive parenting, but because they are likely to promote modeling, reinforcement, shared attention, and social cooperation.

Population differences may occur in older children, if, for example, they have learned that it is appropriate for boys to express emotion or behave differently from girls, or if customs learned by children of one ethnic group are different from those learned in another. Social and emotional differences between boys and girls of a given age may also be associated with differences in the timing of puberty characteristic of the two sexes.

Gender identity is how a person perceives themselves as male, female, or a variation of the two. Studies have found that children can identify themselves as belonging to a certain gender as early as two years old, but how gender identity is developed is a current topic of scientific debate. It is believed that several factors work in conjunction with one another to produce an individual's gender, including: neonatal hormones, postnatal socialization, and genetic influences. However, even the timeline for developing gender is under debate. Some believe that gender is malleable until late childhood, while others argue that gender is established early and gender-typed socialization patterns either reinforce or soften the individual's notion of gender. Since most people identify as the gender that is typically associated to their genitalia, studying the impact of these factors is difficult. Evidence suggests that neonatal androgens, male sex hormones produced in the womb during gestation, play an important role. Testosterone in the womb directly codes the brain for either male or female-typical development. This includes both the physical structure of the brain and the characteristics the person expresses because of it. Persons exposed to high levels of testosterone during gestation typically develop a male gender identity while those who are not or those who do not possess the receptors necessary to interact with these hormones typically develop a female gender identity. An individual's genes are also hypnotized to interact with the hormones during gestation and in turn affect gender identity, but the genes responsible for this and their effects have not been precisely documented and evidence is limited. Postnatal, there is debate on whether socialization plays a part in determining gender identity. It is well documented that children actively seek out information on how to properly interact with others based on their gender, but the extent to which these role models, which can include parents, friends, and TV characters, influence gender identity is less clear and no consensus has been reached in the scientific field.

Language serves the purpose of communication to express oneself through a systematic and traditional use of sounds, signs, or written symbols. There are four subcomponents in which the child must attain in order to acquire language competence. They include phonology, lexicon, morphology and syntax, and pragmatics. These subcomponents of language development are combined to form the components of language, which are sociolinguistics and literacy. Currently, there is no single accepted theory of language acquisition but various explanations of language development have been accumulated.

The four components of language development include:

Children's development of language also includes semantics which is the attachment of meaning to words. This happens in three stages. First, each word means an entire sentence. For example, a young child may say “mama” but the child may mean “Here is Mama”, “Where is Mama?”, or “I see Mama.” In the second stage, words have meaning but do not have complete definitions. This stage occurs around age two or three. Third, around age seven or eight, words have adult-like definitions and their meanings are more complete.

A child learns the syntax of their language when they are able to join words together into sentences and understand multiple-word sentences said by other people. There appear to be six major stages in which a child's acquisition of syntax develops. First, is the use of sentence-like words in which the child communicates using one word with additional vocal and bodily cues. This stage usually occurs between 12 and 18 months of age. Second, between 18 months to two years, there is the modification stage where children communicate relationships by modifying a topic word. The third stage, between two and three years old, involves the child using complete subject-predicate structures to communicate relationships. Fourth, children make changes on basic sentence structure that enables them to communicate more complex relationships. This stage occurs between the ages of two and a half years to four years. The fifth stage of categorization involves children aged three and a half to seven years refining their sentences with more purposeful word choice that reflects their complex system of categorizing word types. Finally, children use structures of language that involve more complicate syntactic relationships between the ages of five years old to ten years old.
Infants begin with cooing and soft vowel sounds. Shortly after birth, this system is developed as the infants begin to understand that their noises, or non-verbal communication, lead to a response from their caregiver. This will then progress into babbling around 5 months of age, with infants first babbling consonant and vowel sounds together that may sound like "ma" or "da". At around 8 months of age, babbling increases to include repetition of sounds, such as "da-da" and infants learn the forms for words and which sounds are more likely to follow other sounds. At this stage, much of the child's communication is open to interpretation. For example, if a child says “bah” when they’re in a toy room with their guardian, it is likely to be interpreted as “ball” because the toy is in sight. However, if you were to listen to the same ‘word’ on a recorded tape without knowing the context, one might not be able to figure out what the child was trying to say. A child's receptive language, the understanding of others' speech, has a gradual development beginning at about 6 months. However, expressive language, the production of words, moves rapidly after its beginning at about a year of age, with a "vocabulary explosion" of rapid word acquisition occurring in the middle of the second year. Grammatical rules and word combinations appear at about age two. Between 20 and 28 months, children move from understanding the difference between high and low, hot and cold and begin to change “no” to “wait a minute”, “not now” and “why”. Eventually, they are able to add pronouns to words and combine them to form short sentences. Mastery of vocabulary and grammar continue gradually through the preschool and school years. Adolescents still have smaller vocabularies than adults and experience more difficulty with constructions such as the passive voice.

By age 1, the child is able to say 1–2 words, responds to its name, imitates familiar sounds and can follow simple instructions. Between 1–2 years old, the child uses 5–20 words, is able to say 2-word sentences and is able to express their wishes by saying words like "more" or "up", and they understand the word "no". During 2 and 3 years of age, the child is able to refer to itself as "me", combine nouns and verbs, has a vocabulary of about 450 words, use short sentences, use some simple plurals and is able to answer "where" questions. By age 4, children are able to use sentences of 4–5 words and has a vocabulary of about 1000 words. Children between the ages of 4 and 5 years old are able to use past tense, have a vocabulary of about 1,500 words, and ask questions like "why?" and "who?". By age 6, the child has a vocabulary of 2,600 words, is able to form sentences of 5–6 words and use a variety of different types of sentences. By the age of 5 or 6 years old, the majority of children have mastered the basics of their native language. Infants, 15 month-olds, are initially unable to understand familiar words in their native language pronounced using an unfamiliar accent. This means that a Canadian-English speaking infant cannot recognize familiar words pronounced with an Australian-English accent. This skill develops close to their second birthdays. However, this can be overcome when a highly familiar story is read in the new accent prior to the test, suggesting the essential functions of underlying spoken language is in place before previously thought.

Vocabulary typically grows from about 20 words at 18 months to around 200 words at 21 months. From around 18 months the child starts to combine words into two-word sentences. Typically the adult expands it to clarify meaning. By 24–27 months the child is producing three or four-word sentences using a logical, if not strictly correct, syntax. The theory is that children apply a basic set of rules such as adding's' for plurals or inventing simpler words out of words too complicated to repeat like "choskit" for chocolate biscuit. Following this there is a rapid appearance of grammatical rules and ordering of sentences. There is often an interest in rhyme, and imaginative play frequently includes conversations. Children's recorded monologues give insight into the development of the process of organizing information into meaningful units.

By three years the child begins to use complex sentences, including relative clauses, although still perfecting various linguistic systems. By five years of age the child's use of language is very similar to that of an adult. From the age of about three children can indicate fantasy or make-believe linguistics, produce coherent personal stories and fictional narrative with beginnings and endings. It is argued that children devise narrative as a way of understanding their own experience and as a medium for communicating their meaning to others. The ability to engage in extended discourse emerges over time from regular conversation with adults and peers. For this, the child needs to learn to combine his perspective with that of others and with outside events and learn to use linguistic indicators to show he is doing this. They also learn to adjust their language depending on to whom they are speaking. Typically by the age of about 9 a child can recount other narratives in addition to their own experiences, from the perspectives of the author, the characters in the story and their own views.

Although the role of adult discourse is important in facilitating the child's learning, there is considerable disagreement among theorists about the extent to which children's early meanings and expressive words arise. Findings about the initial mapping of new words, the ability to decontextualize words, and refine meaning of words are diverse. One hypothesis is known as the syntactic bootstrapping hypothesis which refers to the child's ability to infer meaning from cues, using grammatical information from the structure of sentences. Another is the multi-route model in which it is argued that context-bound words and referential words follow different routes; the first being mapped onto event representations and the latter onto mental representations. In this model, parental input has a critical role but the children ultimately rely on cognitive processing to establish subsequent use of words. However, naturalistic research on language development has indicated that preschoolers' vocabularies are strongly associated with the number of words addressed to them by adults.

There is no single accepted theory of language acquisition. Instead, there are current theories that help to explain theories of language, theories of cognition, and theories of development. They include the generativist theory, social interactionist theory, usage-based theory (Tomasello), connectionist theory, and behaviorist theory (Skinner). Generativist theories refer to Universal Grammar being innate where language experience activates innate knowledge. Social interactionist theories define language as a social phenomenon. This theory states that children acquire language because they want to communicate with others; this theory is heavily based on social-cognitive abilities that drive the language acquisition process. Usage-based theories define language as a set of formulas that emerge from the child's learning abilities in correspondence with its social cognitive interpretation and understanding of the speakers’ intended meanings. Connectionist theories is a pattern-learning procedure and defines language as a system composed of smaller subsystems or patterns of sound or meaning. Behaviorist theories define language as the establishment of positive reinforcement, but is now regarded a theory of historical interest.

Communication can be defined as the exchange and negotiation of information between two or more individuals through verbal and nonverbal symbols, oral and written (or visual) modes, and the production and comprehension processes of communication. According to First International Congress for the Study of Child Language, “the general hypothesis [is that] access to social interaction is a prerequisite to normal language acquisition”. Principles of conversation include two or more people focusing on one topic. All questions in a conversation should be answered, comments should be understood or acknowledged and any form of direction should, in theory, be followed. In the case of young, undeveloped children, these conversations are expected to be basic or redundant. The role of a guardians during developing stages is to convey that conversation is meant to have a purpose, as well as teaching them to recognize the other speaker's emotions. Communicative language is nonverbal and/or verbal, and to achieve communication competence, four components must be met. These four components of communication competence include: grammatical competence (vocabulary knowledge, rules of word sentence formation, etc.), sociolinguistic competence (appropriateness of meanings and grammatical forms in different social contexts), discourse competence (knowledge required to combine forms and meanings), and strategic competence (knowledge of verbal and nonverbal communication strategies). The attainment of communicative competence is an essential part of actual communication.

Language development is viewed as a motive to communication, and the communicative function of language in-turn provides the motive for language development. Jean Piaget uses the term “acted conversations” to explain a child's style of communication that rely more heavily on gestures and body movements, rather than words. Younger children depend on gestures for a direct statement of their message. As they begin to acquire more language, body movements take on a different role and begin to complement the verbal message. These nonverbal bodily movements allow children to express their emotions before they can express them verbally. The child's nonverbal communication of how they’re feeling is seen in babies 0 to 3 months who use wild, jerky movements of the body to show excitement or distress. This develops to more rhythmic movements of the entire body at 3 to 5 months to demonstrate the child's anger or delight. Between 9–12 months of age, children view themselves as joining the communicative world. Before 9–12 months, babies interact with objects and interact with people, but they do not interact with people about objects. This developmental change is the change from primary intersubjectivity (capacity to share oneself with others) to secondary intersubjectivity (capacity to share one's experience), which changes the infant from an unsociable to socially engaging creature. Around 12 months of age a communicative use of gesture is used. This gesture includes communicative pointing where an infant points to request something, or to point to provide information. Another gesture of communication is presented around the age of 10 and 11 months where infants start gaze-following; they look where another person is looking. This joint attention result in changes to their social cognitive skills between the ages of 9 and 15 months as their time is spent increasingly with others. Children's use of non-verbal communicative gestures foretells future language development. The use of non-verbal communication in the form of gestures indicate the child's interest in communication development, and the meanings they choose to convey that are soon revealed through the verbalization of language.

Language acquisition and development contribute to the verbal form of communication. Children originate with a linguistic system where words they learn, are the words used for functional meaning. This instigation of speech has been termed pragmatic bootstrapping. According to this, children view words as a means of social construction, and that words are used to connect the understanding of communicative intentions of the speaker who speaks a new word. Hence, the competence of verbal communication through language is achieved through the attainability of syntax or grammar. Another function of communication through language is pragmatic development. Pragmatic development includes the child's intentions of communication before he/she knows how to express these intentions, and throughout the first few years of life both language and communicative functions develop.

When children acquire language and learn to use language for communicative functions (pragmatics), children also gain knowledge about the participation in conversations and relating to past experiences/events (discourse knowledge), and how to use language appropriately in congruence with their social situation or social group (sociolinguistic knowledge). Within the first two years of life, a child's language ability progresses and conversational skills, such as the mechanics of verbal interaction, develop. Mechanics of verbal interaction include taking turns, initiating topics, repairing miscommunication, and responding to lengthen or sustain dialogue. Conversation is asymmetrical when a child interacts with an adult because the adult is the one to create structure in the conversation, and to build upon the child's contributions. In accordance to the child's developing conversational skills, asymmetrical conversation between adult and child modulate to an equal temperament of conversation. This shift in balance of conversation suggests a narrative discourse development in communication. Ordinarily, the development of communicative competence and the development of language are positively correlated with one another, however, the correlation is not flawless.

Delays in language is the most frequent type of developmental delay. According to demographics 1 out of 5 children will learn to talk or use words later than other children their age. Speech/language delay is three to four times more common in boys than in girls. Some children will also display behavioral problems due to their frustration of not being able to express what they want or need.

Simple speech delays are usually temporary. Most cases are solved on their own or with a little extra attribution from the family. It's the parent's duty to encourage their baby to talk to them with gestures or sounds and for them to spend a great amount of time playing with, reading to, and communicating with their baby. In certain circumstances, parents will have to seek professional help, such as a speech therapist.

It is important to take into considerations that sometimes delays can be a warning sign of more serious conditions that could include auditory processing disorders, hearing loss, developmental verbal dyspraxia, developmental delay in other areas, or even an autism spectrum disorder (ASD).

There are many environmental causes that are linked to language delays and they include situations such as, the child is having their full attention on other skills, such as walking perfectly, rather than on language. The child may have a twin or a sibling in which their age are relatively close, and may not be receiving the parent's full attention. Another circumstance could be a child that is in a daycare that provides few adults to be able to administer individual attention. Perhaps the most obvious component would be a child that suffers from psychosocial deprivation such as poverty, malnutrition, poor housing, neglect, inadequate linguistic stimulation, or emotional stress.

Language delay can be caused by a substantial amount of underlying disorders, such as intellectual disability. Intellectual disability takes part for more than 50 percent of language delays. Language delay is usually more rigorous than other developmental delays in intellectually disabled children, and it is usually the first obvious symptom of intellectual disability. Intellectual disability accounts to global language delay, including delayed auditory comprehension and use of gestures.

Impaired hearing is one of the most common causes of language delay. A child who can not hear or process speech in a clear and consistent manner will have a language delay. Even the most minimum hearing impairment or auditory processing deficit can considerably affect language development. Essentially, the more the severe the impairment, the more serious the language delay. Nevertheless, deaf children that are born to families who use sign language develop infant babble and use a fully expressive sign language at the same pace as hearing children.

Developmental Dyslexia is a developmental reading disorder that occurs when the brain does not properly recognize and process the graphic symbols chosen by society to represent the sounds of speech. Children with dyslexia may encounter problems in rhyming and separating sounds that compose words. These abilities are essential in learning to read. Early reading skills rely heavily on word recognition. When using an alphabet writing system this involves in having the ability to separate out the sounds in words and be able to match them with letter and groups of letters. Because they have trouble in connecting sounds of language to the letter of words, this may result difficulty in understanding sentences. They have confusion in mistaking letters such as "b" and "d". For the most part, symptoms of dyslexia may include, difficulty in determining the meaning of a simple sentence, learning to recognize written words, and difficulty in rhyming.

Autism and speech delay are usually correlated. Problems with verbal language are the most common signs seen in autism. Early diagnosis and treatment of autism can significantly help the child improve their speech skills. Autism is recognized as one of the five pervasive developmental disorders, distinguished by problems with language, speech, communication and social skills that present in early childhood. Some common autistic syndromes are the following, being limited to no verbal speech, echolalia or repeating words out of context, problems responding to verbal instruction and may ignore others who speak directly.

Malnutrition, maternal depression and maternal substance abuse are three of these factors which have received particular attention by researchers, however, many more factors have been considered.

Although there are a large number of studies contemplating the effect of maternal depression and postnatal depression of various areas of infant development, they are yet to come to a consensus regarding the true effects. There are numerous studies indicating impaired development, and equally, there are many proclaiming no effect of depression on development.
A study of 18-month-olds whose mothers suffered depressive symptoms while they were 6 weeks and/or 6 months old indicated that maternal depression had no effect on the child's cognitive development at 18 months. Furthermore, the study indicates that maternal depression combined with a poor home environment is more likely to have an effect on cognitive development. However, the authors conclude that it may be that short term depression has no effect, where as long term depression could cause more serious problems. A further longitudinal study spanning 7 years again indicate no effect of maternal depression on cognitive development as a whole, however it found a gender difference in that boys are more susceptible to cognitive developmental issues when their mothers suffer depression.
This thread is continued in a study of children up to 2 years old. The study reveals a significant difference on cognitive development between genders, with girls having a higher score, however this pattern is found regardless of the child's mother's history of depression. Infants with chronically depressed mothers showed significantly lower scores on the motor and mental scales within the Bayley Scales of Infant Development, contrasting with many older studies. A similar effect has been found at 11 years: male children of depressed mothers score an average of 19.4 points lower on an Intelligence Quotient IQ test than those with healthy mothers, although this difference is much lower in girls. 3 month olds with depressed mothers show significantly lower scores on the Griffiths Mental Development Scale, which covers a range of developmental areas including cognitive, motor and social development. It has been suggested that interactions between depressed mothers and their children may affect social and cognitive abilities in later life.
Maternal depression has been shown to influence the mothers’ interaction with her child. When communicating with their child, depressed mothers fail to make changes to their vocal behaviour, and tend use unstructured vocal behaviours. Furthermore, when infants interact with depressed mothers they show signs of stress, such as increased pulse and raised cortisol levels, and make more use of avoidance behaviours, for example looking away, compared to those interacting with healthy mothers. The effect of mother-infant interaction at 2 months has been shown to affect the child's cognitive performance at 5 years. Recent studies have begun to identify that other forms of psychopathology that may or may not be co-morbidly occurring with maternal depression can independently influence infants' and toddlers' subsequent social-emotional development through effects on regulatory processes within the child-parent attachment. Maternal interpersonal violence-related post-traumatic stress disorder (PTSD), for example, has been associated with subsequent dysregulation of emotion and aggression by ages 4–7 years.

Research has provided conflicting evidence regarding the effect of maternal substance abuse during and after pregnancy on children's development. Children exposed to cocaine weigh less than those not exposed at numerous ages ranging from 6 to 30 months. Furthermore, studies indicate that the head circumference of children exposed to cocaine is lower than those unexposed. On the other hand, two more recent studies found no significant differences between those exposed to cocaine and those who were not in either measure.
Maternal cocaine use may also affect the child's cognitive development, with exposed children achieving lower scores on measures of psychomotor and mental development. However, again there is conflicting evidence, and a number of studies indicate no effect of maternal cocaine use on their child's cognitive development.
Motor development can be imapired by maternal cocaine abuse. As is the case for cognitive and physical development, there are also studies showing no effect of cocaine use on motor development.

The use of cocaine by pregnant women is not the only drug that can have a negative effect on the fetus. Tobacco, marijuana, and opiates are also the types of drugs that can effect an unborn child's cognitive and behavioral development. Smoking tobacco increases pregnancy complications including low birth rate, prematurity, placental abruption, and intrauterine death. It can also cause disturbed maternal-infant interaction; reduced IQ, ADHD, and it can especially cause tobacco use in the child. Parental marijuana exposure may have long-term emotional and behavioral consequences. A ten-year-old child who had been exposed to the drug during pregnancy reported more depressive symptoms than fetuses unexposed. Some short-term effects include executive function impairment, reading difficulty, and delayed state regulation. An opiate drug, such as heroin, decreases birth weight, birth length, and head circumference when exposed to the fetus. Parental opiate exposure has greater conflicting impact than parental cocaine exposure on the infant's Central Nervous System and autonomic nervous system. There are also some negative consequences on a child that you wouldn’t think of with opiates, such as: less rhythmic swallowing, strabismus, and feelings of rejection.

Poor nutrition early in life contributes to stunting, and by the age of two or three can be associated with cognitive deficits, poor school achievement, and poor social relationships later in life Malnutrition is a large problem in developing nations, and has an important effect on young children's weight and height.Children suffering malnutrition in Colombia weighed less than those living in upper class conditions at the age of 36 months (11.88 kg compared to 14 kg), similarly, malnourished children were shorter than well-nourished children, again at 36 months (85.3 cm in malnourished children; 94 cm in well-nourished children
Malnutrition has been indicated as a negative influence on childhood Intelligence Quotient IQ. Although it is now suggested that this effect is nullified when parental IQ is considered, implying that this difference is genetic.

The effect of low iron levels on cognitive development and IQ is a subject still to reach consensus. Some evidence suggests that well-nourished children with lower levels of iron and folate (although not at such a level to be considered deficient) have a lower IQ than those with higher levels of iron and folate. Furthermore, anaemic children perform worse on cognitive measures than non-anaemic children. These nutrients have been strongly implicated in brain development, along with iodine and zinc. Iodine is required for the generation of thyroid hormones necessary for brain development. Iodine deficiency may reduce IQ by an average of 13.5 points compared to healthy individual. Zinc deficiency has also been shown to slow childhood growth and development.

Socioeconomic status is measured primarily based on the factors of income, educational attainment and occupation. Current investigations into the role of socioeconomic factors on child development repeatedly show that continual poverty is more harmful on Intelligence Quotient IQ, and cognitive abilities than short-lived poverty.
Children in families who experience persistent financial hardships and poverty have significantly impaired cognitive abilities compared to those in families who do not face this issue. Low income poverty can cause a number of further issues shown to effect child development, such as poor academic success, less family involvement, iron deficiency, infections, a lack of stimulation, malnutrition and lead poisoning due to lead paint found on the walls of some houses. Child blood levels of lead increase as income decreases. Income poverty is associated with a 6–13 point reduction in IQ for those earning half of the poverty threshold compared to those earning twice the poverty threshold. That being said, children coming from households featuring continual or temporary poverty still perform lower than children in middle-class families.

Parental educational attainment is the most significant socioeconomic factor in predicting the child's cognitive abilities, those with a mother with high IQ are likely to have higher IQs themselves. Similarly, maternal occupation is associated with better cognitive achievement. Those whose mothers’ job entails problem-solving are more likely to be given stimulating tasks and games, and are likely to achieve more advanced verbal competency.

Mother's employment is associated with slightly lower test scores, regardless of socioeconomic status. However, those whose working mother is of a higher socioeconomic status experience more disadvantages because they are being removed from a more enriching environment than a child care. Obviously, the quality of child care is a factor to be considered. Low income children tend to be cared for by grandparents or extended family and therefore form strong bonds with family. High income children tend to be cared for in a child care setting or in home care such as a nanny. If the mother is highly educated, this can be a disadvantage to the child. Even with quality of care controlled for, studies still found a negative correlation between full-time work within the first year and child development. Children whose mothers work are also less likely to receive regular well-baby doctor visits and less likely to be breastfed, which has been proven to improve developmental factors. Effects are felt more strongly when women resume full-time work within the first year of the child's life. These effects may be due in part to pre-existing differences between mothers who return to work and those who do not such as differences in character or reason for returning to work.

Low-income families are less likely to provide a stimulating home learning environment to their children due to time constraints and financial stress. Compared to two-parent households, children with a single-parent generally don't have better social, behavioral, educational, or cognitive outcomes than those with two parents because of economic vulnerability and a lack of parental involvement. A child's academic achievement is influenced by parents' educational attainment, parenting style, and parental investment in their child's cognitive and educational success. Upper-income families are able to afford learning opportunities inside and outside of the classroom. Poverty-stricken children are subjected to fewer stimulating recreational activities, often missing out on trips to libraries or museums, and are unable to access a tutor to help with problematic academic areas.

A further factor in a child's educational attainment involves the school environment, more specifically teacher expectations and attitudes. It has been argued that teachers perceive low-SES children as being less academically able and as such provide them with less attention and reinforcement. On the other hand, it has been found that when schools make an effort to increases family and school involvement, children perform better on state tests.

Diarrhea caused by the parasitic disease Giardiasis is associated with lower IQ. Parasitic worms (helminths) are associated with nutritional deficiencies that are known to be a risk to child development. In particular, intestinal parasitism being one of the most neglected tropical diseases in the developed world. Harboring of this parasite could adverse several health implications in children affecting childhood development and morbidity. Reducing the prevalence of the parasite can be a benefit in child growth, development, and educational outcome.

High levels of lead in the blood is associated with attention deficits, while arsenic poisoning has a negative effect on verbal and full Intelligence Quotient IQ. Manganese poisoning due to levels in drinking water is also associated with a reduced IQ of 6.2 points between the highest and lowest level of poisoning.
Prenatal exposure to various pesticides including organophosphates, and chlorpyrifos has also been linked to reduced IQ score. Organophosphates have been specifically linked to poorer working memory, verbal comprehension, perceptual reasoning and processing speed.

Cognitive development is related to childhood exposure to violence and trauma, including spousal abuse between the parents and sexual abuse.
Intrauterine growth retardation is associated with learning deficits in childhood, and as such, is related to lower IQ.

When a child is unable to meet their developmental goals, because they have not been provided with the correct amount of care, stimulation or nutrition this situation is commonly referred to as child neglect. It is the most widespread form of child abuse. Neglect accounted for 78% of all child abuse cases in the United States in 2010 alone. Scientific Studies show that exposure to child neglect can have lifelong consequences for children.

Assessing and identifying neglect pose a number of challenges for practitioners. Given that neglect is a dynamic between the child's development and levels of nurturance, the question in identifying neglect, becomes one of where do you start, with the child's development or with the levels of nurturance?

Some professionals identify neglect by measuring the developmental levels of a child, for if those developmental levels are normal, one can, by definition, conclude that a child is not being neglected. Areas of development that could be measured include weight, height, stamina, social & emotional responses, speech and motor development. All these features go up to make a medical assessment of whether a child is thriving, so that a professional looking to start an assessment of neglect, might reasonably start with information collected by a doctor. Infants are often weighed and measured when seen by their physicians for well-baby check-ups. The physician initiates a more complete evaluation when the infant's development and functioning are found to be delayed. What this suggests is that social work staff could consult medical notes to establish if the baby or child is failing to thrive, as a first step in a pathway towards identifying neglect. If developmental levels are subnormal, then the identification of neglect then requires the professional establish if those subnormal levels of development can be put down to the level of nurturance experienced by the child. One needs to discount that the developmental delay was caused by some genetic condition or disease, which do not have their basis in a lack of nurturance.

Another way of starting a process for identifying neglect is to identify if the child in question is experiencing a level of nurturance lower than that considered necessary to support normal development. In part this requires a knowledge of the level of nurturance required by the child to sustain normal development, which might be particular to his or her age, gender and other factors. However quite how one ascertains what a particular child needs, without referring back to their level of development, is not something theory and policy on neglect is clear about. Furthermore, ascertaining whether a child is getting the requisite level of nurturance needs to take into account not just the intensity of the nurturance, but also, given that the intensity of certain forms of nurturance can vary across time, the duration and frequency of the nurturance. It is acceptable for a child to experience varying and low levels of certain types of nurturance across a day and from time to time, however, the levels of nurturance should never cross thresholds of intensity, duration and frequency. For this reason, professionals are minded to keep detailed histories of care provision, which demonstrate the duration to which the child is exposed to periods of subnormal exposure to care, stimulation, and nutrition.

It is most common for guidance to suggest professionals should focus on the levels of nurturance provided by the carers of the child, where neglect is understood as an issue of the parents' behaviour towards the child. Some authors feel that establishing the failure of parents and caregivers to provide care would be sufficient to conclude that neglect was occurring. Action for Children state that, "A child experiences neglect when the adults who look after them fail to meet their needs" clearly defining neglect as a matter of parental performance. This raises the question about what level of nurturance, a carer or parent needs to fall under, to provoke developmental delay, and how one goes about measuring that accurately.

The method, which focuses on the stimulation provided by the carer, can be subject to critique. Neglect is about the child's development being adversely affected by the levels of nurturance, but the carers' provision of nurturance is not always a good indicator of the level of nurturance received by the child. Neglect may be occurring at school, outside of parental care. The child may be receiving nurturance from siblings or through a boarding school education, which compensates for the lack of nurturance provided by the parents.

Neglect is a process whereby children experience developmental delay owing to experiencing insufficient levels of nurturance. It has been argued that in principle, this means that when starting an assessment of neglect by identifying developmental delay one needs to then check the levels of nurturance received by the child. Certainly, where guidance on identifying neglect does urge for practitioners to measure developmental levels, some guidance urges practitioners to focus on how developmental levels can be attributed to parental behaviour. However, the narrow focus on parental behaviour can be criticised for unnecessarily ruling out the possible effect of institutionalised neglect, e.g. neglect at school.

If one starts by concluding that the levels of nurture received by the child are insufficient, one then needs to consider the developmental levels achieved by the child.

Further challenges arise, however. Even when one has established developmental delay and exposure to low levels of nurture, one needs to rule out the possibility that the link between the two is coincidental. The developmental delay may be caused by a genetic disorder, disease or physical, sexual or emotional abuse. Of course, the developmental delay may be caused by a mixture of underexposure to nurture, abuse, genetics and disease.

The Graded Care Profile Tool is a practice tool which gives an objective measure of the quality of care in terms of a parent/carer's commitment. It was developed in the UK.

The North Carolina Family Assessment Scale is a tool which can be used by a practitioner to explore whether neglect is taking place across a range of family functioning areas.

Early intervention programs and treatments in developed countries include individual counselling, family, group counselling and social support services, behavioural skills training programs to eliminate problematic behaviour and teach parents "appropriate" parenting behaviour.

Video interaction guidance is a video feedback intervention through which a "guider" helps a client to enhance communication within relationships. The client is guided to analyse and reflect on video clips of their own interactions. Video Interaction Guidance has been used where concerns have been expressed over possible parental neglect in cases where the focus child is aged 2–12, and where the child is not the subject of a child protection plan.

The SafeCare programme is a preventative programme working with parents of children under 6 years old who are at risk of experiencing significant harm through neglect. The programme is delivered in the home by trained practitioners, over 18 to 20 sessions and focuses on 3 key areas: parent-infant/child interaction; home safety and child health.

Triple P (Parenting Program) is a positive parenting program. It is a multilevel, parenting and family support strategy. The idea behind it is that if parents are educated on "proper" parenting and given the appropriate resources, it could help decrease the amount of child neglect cases. When deciding whether to leave a child home alone, caregivers need to consider the child's physical, mental, and emotional well-being, as well as state laws and policies regarding this issue.

Attachment is a deep emotional bond between two people, a "lasting psychological connectedness between human beings." Attachment theory, developed by John Bowlby during the 1950s, is a theory that remains influential in psychology today.

Social connection

Social connection is the experience of feeling close and connected to others. It involves feeling loved, cared for, and valued, and forms the basis of interpersonal relationships.

Increasingly, social connection is understood as a core human need, and the desire to connect as a fundamental drive. It is crucial to development; without it, social animals experience distress and face severe developmental consequences. In humans, one of the most social species, social connection is essential to nearly every aspect of health and well-being. Lack of connection, or loneliness, has been linked to inflammation, accelerated aging and cardiovascular health risk, suicide, and all these factors cause mortality.

Feeling socially connected is related to the quality and number of connections one has with family, friends, and acquaintances. Going beyond the individual level, it also involves a feeling of connecting to a larger community. Connectedness on a community level benefits both individuals and society.

Social support is the help, advice, and comfort that we receive from those with whom we have stable, positive relationships. Importantly, it appears to be the perception, or "feeling," of being supported, rather than objective number of connections, that appears to buffer stress and affect our health and psychology most strongly.

Close relationships refer to those relationships between friends or romantic partners that are characterized by love, caring, commitment, and intimacy.

In his influential theory on the hierarchy of needs, Abraham Maslow proposed that our physiological needs are the most basic and necessary to our survival, and must be satisfied before we can move on to satisfying more complex social needs like love and belonging. However, research over the past few decades has begun to shift our understanding of this hierarchy. Social connection and belonging may in fact be a basic need, as powerful as our need for food or water. Mammals are born relatively helpless, and rely on their caregivers not only for affection, but for survival. This may be evolutionarily why mammals need and seek connection, and also for why they suffer prolonged distress and health consequences when that need is not met.

In 1965, Harry Harlow conducted his landmark monkey studies. He separated baby monkeys from their mothers, and observed which surrogate mothers the baby monkeys bonded with: a wire "mother" that provided food, or a cloth "mother" that was soft and warm. Overwhelmingly, the baby monkeys preferred to spend time clinging to the cloth mother, only reaching over to the wire mother when they became too hungry to continue without food. This study questioned the idea that food is the most powerful primary reinforcement for learning. Instead, Harlow's studies suggested that warmth, comfort, and affection (as perceived from the soft embrace of the cloth mother) are crucial to the mother-child bond, and may be a powerful reward that mammals may seek in and of itself. Although historic, it is important to acknowledge that this study does not meet current research standards for the ethical treatment of animals.

In 1995, Roy Baumeister proposed his influential belongingness hypothesis: that human beings have a fundamental drive to form lasting relationships, to belong. He provided substantial evidence that indeed, the need to belong and form close bonds with others is itself a motivating force in human behavior. This theory is supported by evidence that people form social bonds relatively easily, are reluctant to break social bonds, and interpret situations with how they affect their relationships in mind. He also contends that our emotions are so deeply linked to our relationships that one of the primary functions of emotion may be to form and maintain social bonds, and that both partial and complete deprivation of relationships leads to not only painful but pathological consequences. Satisfying or disrupting our need to belong, our need for connection, has been found to influence cognition, emotion, and behavior.

While it appears that social isolation triggers a "neural alarm system" of threat-related regions of the brain (including the amygdala, dorsal anterior cingulate cortex (dACC), anterior insula, and periaqueductal gray (PAG)), separate regions may process social connection. Two brain areas that are part of the brain's reward system are also involved in processing social connection and attention to loved ones: the ventromedial prefrontal cortex (VMPFC), a region that also responds to safety and inhibits threat responding, and the ventral striatum (VS) and septal area (SA), part of a neural system that is activated by taking care of one's own young.

In 1978, neuroscientist Jaak Panksepp observed that small doses of opiates reduced the distressed cries of puppies that were separated from their mothers. As a result, he developed the brain opioid theory of attachment, which posits that endogenous (internally produced) opioids underlie the pleasure that social animals derive from social connection, especially within close relationships. Extensive animal research supports this theory. Mice who have been genetically modified to not have mu-opioid receptors (mu-opioid receptor knockout mice), as well as sheep with their mu-receptors blocked temporarily following birth, do not recognize or bond with their mother. When separated from their mother and conspecifics, rats, chicks, puppies, guinea pigs, sheep, dogs, and primates emit distress vocalizations, however giving them morphine (i.e. activating their opioid receptors), quiets this distress. Endogenous opioids appear to be produced when animals engage in bonding behavior, while inhibiting the release of these opioids results in signs of social disconnection. In humans, blocking mu-opioid receptors with the opioid antagonist, naltrexone, has been found to reduce feelings of warmth and affection in response to a film clip about a moment of bonding, and to increase feelings of social disconnection towards loved ones in daily life as well as in the lab in response to a task designed to elicit feelings of connection. Although the human research on opioids and bonding behavior is mixed and ongoing, this suggests that opioids may underlie feelings of social connection and bonding in humans as well.

In mammals, oxytocin has been found to be released during childbirth, breastfeeding, sexual stimulation, bonding, and in some cases stress. In 1992, Sue Carter discovered that administering oxytocin to prairie voles would accelerate their monogamous pair-bonding behavior. Oxytocin has also been found to play many roles in the bonding between mother and child. In addition to pair-bonding and motherhood, oxytocin has been found to play a role in prosocial behavior and bonding in humans. Nicknamed the “love drug” or “cuddle chemical,” plasma levels of oxytocin increase following physical affection, and are linked to more trusting and generous social behavior, positively biased social memory, attraction, and anxiety and hormonal responses. Further supporting a nuanced role in adult human bonding, greater circulating oxytocin over a 24-hour period was associated with greater love and perceptions of partner responsiveness and gratitude, however was also linked to perceptions of a relationship being vulnerable and in danger. Thus oxytocin may play a flexible role in relationship maintenance, supporting both the feelings that bring us closer and the distress and instinct to fight for an intimate bond in peril.

A wide range of mammals, including rats, prairie voles, guinea pigs, cattle, sheep, primates, and humans, experience distress and long-term deficits when separated from their parent. In humans, long-lasting health consequences result from early experiences of disconnection. In 1958, John Bowlby observed profound distress and developmental consequences when orphans lacked warmth and love of our first and most important attachments: our parents. Loss of a parent during childhood was found to lead to altered cortisol and sympathetic nervous system reactivity even a decade later, and affect stress response and vulnerability to conflict as a young adult.

In addition to the health consequences of lacking connection in childhood, chronic loneliness at any age has been linked to a host of negative health outcomes. In a meta-analytic review conducted in 2010, results from 308,849 participants across 148 studies found that people with strong social relationships had a 50% greater chance of survival. This effect on mortality is not only on par with one of the greatest risks, smoking, but exceeds many other risk factors such as obesity and physical inactivity. Loneliness has been found to negatively affect the healthy function of nearly every system in the body: the brain, immune system, circulatory and cardiovascular systems, endocrine system, and genetic expression.

Not only is social isolation harmful to health, but it is more and more common. As many as 80% of young people under 18 years old, and 40% of adults over the age of 65 report being lonely sometimes, and 15–30% of the general population feel chronic loneliness. These numbers appear to be on the rise, and researchers have called for social connection to be public health priority.

One of the main ways social connection may affect our health is through the immune system. The immune system's primary activity, inflammation, is the body's first line of defense against injury and infection. However, chronic inflammation has been tied to atherosclerosis, Type II diabetes, neurodegeneration, and cancer, as well as compromised regulation of inflammatory gene expression by the brain. Research over the past few decades has revealed that the immune system not only responds to physical threats, but social ones as well. It has become clear that there is a bidirectional relationship between circulating biomarkers of inflammation (e.g. the cytokine IL-6) and feelings of social connection and disconnection; not only are feelings of social isolation linked to increased inflammation, but experimentally induced inflammation alters social behavior and induces feelings of social isolation. This has important health implications. Feelings of chronic loneliness appear to trigger chronic inflammation. However, social connection appears to inhibit inflammatory gene expression and increase antiviral responses. Performing acts of kindness for others were also found to have this effect, suggesting that helping others provides similar health benefits.

Why might our immune system respond to our perceptions of our social world? One theory is that it may have been evolutionarily adaptive for our immune system to "listen" in to our social world to anticipate the kinds of bacterial or microbial threats we face. In our evolutionary past, feeling socially isolated may have meant we were separated from our tribe, and therefore more likely to experience physical injury or wounds, requiring an inflammatory response to heal. On the other hand, feeling connected may have meant we were in relative physical safety of community, but at greater risk of socially transmitted viruses. To meet these threats with greater efficiency, the immune system responds with anticipatory changes. A genetic profile was discovered to initiate this pattern of immune response to social adversity and stress — up-regulation of inflammation, down-regulation of antiviral activity — known as Conserved Transcriptional Response to Adversity. The inverse of this pattern, associated with social connection, has been linked to positive health outcomes as well as eudaemonic well-being.

Social connection and support have been found to reduce the physiological burden of stress and contribute to health and well-being through several other pathways as well, although there remains a subject of ongoing research. One way social connection reduces our stress response is by inhibiting activity in our pain and alarm neural systems. Brain areas that respond to social warmth and connection (notably, the septal area) have inhibitory connections to the amygdala, which have the structural capacity to reduce threat responding.

Another pathway by which social connection positively affects health is through the parasympathetic nervous system (PNS), the "rest and digest" system which parallels and offsets the "flight or fight" sympathetic nervous system (SNS). Flexible PNS activity, indexed by vagal tone, helps regulate the heart rate and has been linked to a healthy stress response as well as numerous positive health outcomes. Vagal tone has been found to predict both positive emotions and social connectedness, which in turn result in increased vagal tone, in an "upward spiral" of well-being. Social connection often occurs along with and causes positive emotions, which themselves benefit our health.

Social Connectedness Scale

This scale was designed to measure general feelings of social connectedness as an essential component of belongingness. Items on the Social Connectedness Scale reflect feelings of emotional distance between the self and others, and higher scores reflect more social connectedness.

UCLA Loneliness Scale

Measuring feelings of social isolation or disconnection can be helpful as an indirect measure of feelings of connectedness. This scale is designed to measure loneliness, defined as the distress that results when one feels disconnected from others.

Relationship Closeness Inventory (RCI)

This measure conceptualizes closeness in a relationship as a high level of interdependence in two people's activities, or how much influence they have over one another. It correlates moderately with self-reports of closeness, measured using the Subjective Closeness Index (SCI).

Liking and Loving Scales

These scales were developed to measure the difference between liking and loving another person—critical aspects of closeness and connection. Good friends were found to score highly on the liking scale, and only romantic partners scored highly on the loving scale. They support Zick Rubin's conceptualization of love as containing three main components: attachment, caring, and intimacy.

Personal Acquaintance Measure (PAM)

This measure identifies six components that can help determine the quality of a person's interactions and feelings of social connectedness with others:Social connection is a unique, elusive, person-specific quality of our social world. Yet, can it be manipulated? This is a crucial question for how it can be studied, and whether it can be intervened on in a public health context. There are at least two approaches that researchers have taken to manipulate social connection in the lab:

Social connection task

This task was developed at UCLA by Tristen Inagaki and Naomi Eisenberger to elicit feelings of social connection in the laboratory. It consists of collecting positive and neutral messages from 6 loved ones of a participant, and presenting them to the participant in the laboratory. Feelings of connection and neural activity in response to this task have been found to rely on endogenous opioid activity.

Closeness-generating procedure

Arthur Aron at the State University of New York at Stony Brook and collaborators designed a series of questions designed to generate interpersonal closeness between two individuals who have never met. It consists of 36 questions that subject pairs ask each other over a 45-minute period. It was found to generate a degree of closeness in the lab, and can be more carefully controlled than connection within existing relationships.

However, when Bowlby developed his attachment theory, cognitive psychology was still at its beginning. Only in 1967, Neisser proposed a theory of mental representation based on schemas which later led to the development of schema theory. It was said that these scripts might be the base of the structure of internal working models.

Internal working model of attachment

Internal working model of attachment is a psychological approach that attempts to describe the development of mental representations, specifically the worthiness of the self and expectations of others' reactions to the self. This model is a result of interactions with primary caregivers which become internalized, and is therefore an automatic process. John Bowlby implemented this model in his attachment theory in order to explain how infants act in accordance with these mental representations. It is an important aspect of general attachment theory.

Such internal working models guide future behavior as they generate expectations of how attachment figures will respond to one's behavior. For example, a parent rejecting the child's need for care conveys that close relationships should be avoided in general, resulting in maladaptive attachment styles.

The most influential figure for the idea of the internal working model of attachment is Bowlby, who laid the groundwork for the concept in the 1960’s. He was inspired by both psychoanalysis, especially object relations theory, and more recent research into ethology, evolution and information-processing.

In psychoanalytic theory, there has been the idea of an inner or representational world (proposed by Freud) as well as the internalization of relationships (Fairbairn, Winnicott). According to Freud first schemata evolve out of experiences regarding need fulfilment via the attachment figure. He argued that the resulting mental representation is an internal copy of the external world made up from memories, and thinking serves the role of experimental action. Fairbairn and Winnicott proposed that these early patterns of relationships become internalized and govern future relationships.

However, the ethological-evolutionary aspects of the theory received more attention. Bowlby was interested in separation distress, and bonding in animals. He noticed that many infant behaviours are organized around the goal of maintaining proximity to the caregiver. He proposed that human infants like other mammals must have an attachment motivational-behavioural system which enhances chances for survival. Ainsworth observed mother-infant interaction and came to the conclusion that individual differences in reaction to separation could not be explained by simple absence or presence of the caregiver but must be the result of a cognitive process.

The term internal working model, however, was coined quite early by Craik (1943). What he called internal working model was a more elaborate and modern version of the psychoanalytical idea of the internal world. In essence, he claimed that humans carry a small-scale representation, or model of reality, and their own potential actions within it in their mind.

In summary, Bowlby remodelled Freud’s work about relationship development in terms of newer fields of research (evolutionary biology, ethology, information-processing theory), drawing both from Craik’s idea of representations as the formation and use of dynamic models and Piaget’s theory of cognitive development.

There are several hypothesized functions of an internal working model of attachment, both in terms of its evolutionary origins and inherent functioning.

Bowlby proposed that proximity-seeking behaviour evolved out of selection pressure. In the context of survival, a healthy internal working model helps the infant to maintain proximity to their caregiver in the face of threat or danger. This is especially important for species with prolonged periods of development, like humans. Due to the relative immaturity of the infant at birth, offspring that manages to maintain a close relationship to their caregiver by seeking their proximity has a survival advantage. A close emotional bond to the caregiver is therefore crucial for protection from physical harm, and thus the internal working model mediates attachment. This regulation is enforced via a motivational-behaviour system, motivating both infant and caregiver to seek proximity. Specifically, caregiving is regulated by behavioural processes complementary to the infant’s proximity-seeking, e.g. the baby smiles, the adult feels reward as a result.

Having an adequate internal model or representation of the self and the caregiver also serves the adaptive function of ensuring appropriate interpretation and prediction of, as well as response to the environment. Craik especially emphasized that those organisms that are capable of forming complex internal working models have higher chances of survival. The better the internal working model can simulate reality the better the individual’s capacity to plan and respond. According to Bowlby individuals form both models of the world and the self within it. These models, initially the product of specific experiences of reality, then aid future attention to and perception and interpretation of the world, which in turn creates certain expectations about possible future events, allowing foresightful and appropriate behaviour. Hence, having adequate representations of the self and caregivers serves an adaptive function.

Lastly, if the infant can be sure about the availability of the attachment figure, it will be less prone to fear due to the supportive presence or secure base function of the caregiver, which makes exploration of the environment and hence learning possible. This felt security is the primary goal of all working models. Ainsworth researched the secure base phenomenon in her strange situation procedure in which an infant uses their mothers as a secure base. The attachment system provides the child with a sense of security in the form of this base, which supports exploration of the environment and hence independence. A securely attached child will, in turn, achieve a balance between intimacy and independence. This corresponds to a balance between the attachment system which serves the function of protection and the exploration system which facilitates learning.

The function of other attachment styles can be explained in terms of an imbalance of intimacy and independence, a preoccupation with one of these goals. This overriding chronic goal is intimacy in preoccupied children, independence or self-protection in dismissive children, and in case of the fearful child, there is a conflicting chronic goal of achieving both intimacy and independence at the same time or an approach-avoidance conflict due to relative inflexibility in comparison to secure attachment.

The internal working model functions largely outside of conscious awareness. Those subconscious aspects might be especially important for the function of self-protection and serve as a defence mechanism in the face of contradicting models, where one of them operates within the subconscious to prevent a threat to the self. This is mostly the case for dismissive-avoidant attachment where conflicting ideas of the caregiver as both loving and neglecting cause the defence mechanism of downplaying the need for intimacy, not relying on the attachment figure, and emphasizing independence.

Infants develop different types of internal working models dependent on two factors: the responsiveness and accessibility of the parent and the worthiness of the self to be loved and supported. Thus, by the age of three years, infants will have developed several expectations about how attachment figures will react to their need for help and start to evaluate how likely the self is worth of support in general. These internalized representations of the self, of attachment figures, and of relationships are constructed as a result of experiences with primary caregivers. It guides the individual’s expectations about relationships throughout life, subsequently influencing social behavior, perception of others and development of self-esteem.

Essentially, four different internal working models can be defined which are based on positive or negative images of self and others. Children who feel securely attached seek their parent as a secure base and are willing to explore their environment. In adulthood, they hold a positive model of self and others, therefore, feeling comfortable with intimacy and autonomy. On the contrary, adults who develop a fearful-avoidant internal working model (negative self/ negative others) construct defense mechanisms in order to protect themselves from being rejected by others. Consequently, they avoid intimate relationships. The third category is classified as the preoccupied model, indicating a combination of negative self-evaluation and the appreciation of others, which makes them overly dependent on their environment. Finally, dismissive-avoidant adults aim for independence as they view themselves as valuable and autonomous. They rarely open up and mainly rely on themselves due to lack of trust in others.

Internal working models are considered to result out of generalized representations of past events between attachment figure and the child. Thus, in forming an internal working model a child takes into account past experiences with the caregiver as well as the outcomes of past attempts to establish contact with the caregiver. One important factor in the establishment of generalized representations is caregiver behaviour. Accordingly, a child whose caretaker exhibits high levels of parental sensitivity, responsiveness and reliability is likely to develop a positive internal working model of the self. Conversely, frequent experiences of unreliability and neglect by the attachment figure foster the emergence of negative internal working models of self and others.

As infants have been shown to possess the social and cognitive capacities necessary to form internal working models, initial development of these may occur within the first year of life. Once established, internal working models are assumed to remain largely consistent over time, developing primarily in complexity and sophistication. As such, internal working models of young children may include representations of past instances of caregiver responsiveness or availability, while older children's and adults' internal working models may integrate more advanced cognitive abilities such as the imagination of hypothetical future interactions. However, changes to internal representations of attachment relationships can occur. This is most likely to happen upon repeated experiences that are incompatible with the internal working model in place at the time. One way this can happen is during major periods (meaning weeks or months) of absence of the attachment figure. During such prolonged absence, a child's expectation of the caregiver's availability to respond is continuously violated. This results in a change of behaviour toward the caregiver upon reunion, reflecting changes in the child's internal working model of the relationship.

Internal working models are subject to intergenerational transmission, meaning that parents' internal working model patterns may be passed on to their children. Indeed, high correlations have been found between security of early infant attachment and parental internal working model security. A central aspect in intergenerational transmission of internal working models is that caretakers themselves are influenced in their behaviour toward children by their own internal working models. For instance, a parent with a secure and consistent internal working model is likely to interpret an infant's attachment signals appropriately, whereas a parent with an insecure internal working model is less likely to do so. In the latter case, the infant itself might be drawn to construct a negative working model of the self and the relationship. Furthermore, a parent with a negative, poorly organized and inconsistent working model might fail to provide useful feedback about the parent-infant dyad and other relationships, thus disrupting the infant's forming of a well-adapted working model at an early stage. The result will be a negative, disorganized internal working model employed by the infant.

One mechanism by which attachment (and thus, internal working models of attachment) can be transmitted is joint reminiscing about past events or memories. For instance, mothers who are securely attached tend to communicate about past events in more elaborate ways than do mothers who are not securely attached. While reminiscing together about past events, securely attached mothers will then engage in more elaborate reasoning with their child, thereby stimulating the development of a more elaborate, coherent internal working model by the child itself.