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Attachment at an Early Age (0-5) and its Impact on Children’s Development

Marinus van Ijzendoorn, PhD

Leiden University, Netherlands

March 2007, 2nd ed.


What is attachment? Children are considered to be attached if they tend to seek proximity to and contact with a specific caregiver in times of distress, illness and tiredness.1 Attachment to a protective caregiver helps infants to regulate their negative emotions in times of stress and distress and to explore the environment, even if it contains somewhat frightening stimuli. Attachment, a major developmental milestone in the child’s life, remains an important issue throughout the lifespan. In adulthood, attachment representations shape the way adults feel about the strains and stresses of intimate relationships, including parent-child relationships, and the way in which the self is perceived.

Development of attachment

Attachment develops in four phases.1 In the first phase — indiscriminately orienting and signalling to people — the baby seems “tuned” to certain wave-lengths of signals from the environment. These signals are mostly of human origin (e.g. the sound of voices). During the second phase, probably first by smell and then by sight, the baby develops preference for one or more caregivers — the phase of orienting and signalling to one or several specific persons. Not until the infant is able to show active attachment behaviour, such as actively seeking proximity to and following the attachment figure, does the infant enters the third phase, the phase of attachment proper — staying near a specific person by means of signalling and movement. Children enter the fourth phase of the goal-corrected partnership when they can imagine the parent or caregiver’s plans and perceptions and fit their own plans and activities according to these.

Explaining individual differences in attachment

Ainsworth et al.2 observed one-year-old infants with their mothers in a standardized stressful separation procedure, the Strange Situation Procedure (SSP). The reactions of the infants to their reunion with the caregiver after a brief separation were used to assess how much trust the children had in the accessibility of their attachment figure.

The procedure consists of eight episodes, of which the last seven ideally take three minutes. Infants are confronted with three stressful components: an unfamiliar environment, interaction with a stranger, and two short separations from the caregiver.

Three patterns of attachment can be distinguished on the basis of infants' reactions to the reunion with the parent or other caregiver. Infants who actively seek proximity to their caregivers on reunion, communicate their feelings of stress and distress openly and then readily return to exploration are classified as secure (B).  Infants who do not seem to be distressed and ignore or avoid the caregiver after being reunited (although physiological research shows their arousal)3 are classified as insecure-avoidant (A). Infants who combine strong contact maintenance with contact resistance, or remain inconsolable without being able to return to explore the environment, are classified as insecure-ambivalent (C). Besides the classic tripartite ABC classifications, Main and Solomon4 proposed a fourth classification, disorganized attachment (D), which is not discussed here.

An overview of all American studies with non-clinical samples (21 samples with a total of 1,584 infants, conducted between 1977 and 1990) shows that about 67% of the infants were classified as secure, 21% as insecure-avoidant and 12% as insecure-ambivalent.5 A central issue in attachment theory and research is what causes some infants to develop an insecure attachment relationship while other infants feel secure.

Research Context

The basic model of explaining differences in attachment relationships assumes that sensitive or insensitive parenting determines infant attachment (in-)security. Ainsworth2 and colleagues originally defined parental sensitivity as the ability to perceive and interpret children’s attachment signals correctly and respond to these signals promptly and adequately. Lack of responsiveness or inconsistent sensitivity has indeed been found to be associated with insecurity in children, and consistent sensitive responsiveness with secure bonds.6

However, some proponents of the behavioural genetic approach have declared most correlational findings on child development to be seriously flawed because they are based on traditional research designs focusing on between-family comparisons, which confound genetic similarities between parents and children with supposedly shared environmental influences.7 Harris,8 for example, claims that there is an urgent need to radically rethink and de-emphasize the role of parents in child development. Despite the prevalence of this  current of thought, attachment theory continues to emphasize the important role of parental sensitivity.

Key Research Questions

Crucial research questions explore the causal role of sensitive parenting in the development of infant attachment security. These questions have been addressed in twin studies comparing attachments of mono- and dizygotic twins within the same family, and in experimental intervention studies designed to enhance parental sensitivity in order to improve the infant attachment relationship.

Recent Research Results

Four twin studies on child-mother attachment security using behavioural genetic modelling have been published to date. Three of the four studies document a minor role for genetic influences on differences in attachment security and a rather substantial role for shared environment.9,10,11  The fourth study, the Louisville Twin Study,12  investigated the quality of attachment in twin pairs with an adapted separation-reunion procedure originally designed to assess temperament. The large role shared environmental factors play in attachment (about 50% in the Bokhorst et al. study)11 is remarkable. Differences in attachment relationships are mainly caused by nurture rather than nature, although the bias to become attached is inborn.

Is sensitive parenting the core ingredient of the shared environment? Twenty-one correlational studies have replicated a significant but modest association between parental sensitivity and infant attachment (r = .24, N = 1099). But only experimental interventions can definitely prove Ainsworth’s original hypothesis. In 24 randomized intervention studies (n = 1280), both maternal sensitivity and children’s attachment security were assessed as outcome measures. In general, attachment insecurity appeared more difficult to change than maternal insensitivity. When interventions were more effective in enhancing parental sensitivity, they were also more effective in enhancing attachment security, which experimentally supports the notion of a causal role of sensitivity in shaping attachment.13


Attachment, the affective bond of infant to parent, plays a pivotal role in the regulation of stress in times of distress, anxiety or illness. Human beings are born with the innate bias to become attached to a protective caregiver. But infants develop different kinds of attachment relationships: some infants become securely attached to their parent, and others find themselves in an insecure attachment relationship. These individual differences are not genetically determined but are rooted in interactions with the social environment during the first few years of life. Sensitive or insensitive parenting plays a key role in the emergence of secure or insecure attachments, as has been documented in twin studies and experimental intervention studies. In the case of attachment theory, the nurture assumption8 is indeed warranted. Numerous findings confirm the core hypothesis that sensitive parenting causes infant attachment security, although other causes should not be ruled out.

Implications for Social Policy

The most important policy and mental-health implication is that parenting does matter for infants’ socio-emotional development. Parents are therefore entitled to receive social support from policy-makers and mental-health workers to do the best job they can in raising their vulnerable children. Sensitive parenting is hard work and does not come naturally to many parents, who have to find their way even if they had few positive childhood experiences of their own. It takes a village to raise a child,14 so parents need to rely on good-quality non-parental care to combine childrearing with other obligations. Furthermore, many parents may profit from rather brief preventive interventions that help them become more sensitive to their infants’ attachment signals. From our meta-analysis, we concluded that the most effective interventions for enhancing sensitive parenting and infant attachment security used a moderate number of sessions and a clear-cut behavioural focus, starting no sooner than six months after birth. From an applied attachment perspective, young parents should be given access to preventive support programs that incorporate these evidence-based insights.


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How to cite this article:

van Ijzendoorn MH. Attachment at an Early Age (0-5) and its Impact on Children’s Development. In: Tremblay RE, Boivin M, Peters RDeV, eds. van IJzendoorn MH, topic ed. Encyclopedia on Early Childhood Development [online]. Updated March 2007. Accessed July 22, 2019.