Bowlby argued that evolutionary pressures have led humans to develop an Attachment Behavioural System which activates behaviours that cause caregivers to remain close when the child is anxious (e.g., crying, clinging, intense protest,  and searching). In other words babies are born with certain automatic behaviours that are triggered by events such as being alone. For example, when the infant finds itself alone it automatically starts crying.

Bowlby also claimed that mothers are genetically predisposed to respond to the baby. Infants are programmed to behave in ways that activate caring responses in adults, these are called "social releasers". Examples of social releasers are smiling, crying, gazing and grasping. So when the infant cries, for example, the mother feels compelled to respond to the infant's needs. Mother-child interactions eventually lead to attachment, since the two way process means that they are kept in close proximity with each other.

Critical Period

A further aspect of Bowlby's theory is the idea of a critical period for attachment to take place. Bowlby was clearly influenced by the ethologist, Konrad Lorenz, who found that Greylag geese would only imprint on moving objects that they saw within 24 hours of hatching.

Bowlby (1951) believed that if attachment formation is delayed for more than 12 months, it is unlikely that a proper attachment will form; however, he argued that sometimes the critical period can last up to 2½ years although this is rare.

Monotropy

Perhaps the most controversial aspect of Bowlby's theory is his concept of monotropy: he believed that babies are programmed to develop a special attachment with one person and that person is usually the mother or another significant female. This relationship is fundamentally different to any other attachment and forms the basis of future relationships:

The Role of Fathers

To Bowlby, fathers are emotionally insignificant to the child, although they can provide emotional and financial support to the mother.

Evaluation of Bowlby's Theory

Recent research using fMRI has shown that the reward centres of mothers' brains are activated when they see their own child smiling, but not when they see other children smiling (Strethearn et al. 2008), this provides tentative support for some of Bowlby's ideas because it shows that there is a biological difference in how mothers perceive their own children.

There is a good deal of evidence that attachment formation is a biological process: attachment develops even if the child is maltreated – children tend to cling when they are frightened or upset and in the absence of anyone else, they will cling to the person maltreating them; external rewards are not required for attachment to develop; attachment is extremely resistant to extinction; and secure attachments tend to foster autonomy rather than dependency (Rutter & Rutter, 1992).

Michael Rutter (1981) has strongly criticised Bowlby’s concept of ‘monotropy’. He claims that infants often show multiple attachments and often the primary attachment is to someone other than the mother and this person can be male. Bowlby did, however, agree that infants can form multiple attachments; nevertheless, Bowlby was adamant that the most important attachment is with the mother.

Shaffer and Emerson (1964) provide empirical support for Rutter's criticisms of Bowlby's theory. They studied 60 infants from birth at intervals of four weeks. The mother reported on the child’s behaviour in a number of situations, such as:

• Infant left alone

• Left with babysitter

• Put to bed

The researchers were particularly interested in the child's protest behaviour:

• Did the infant protest when someone left?

• Whose departure resulted in protest?

• How much did the infant protest?

It was found that infants were often attached to people who did not perform caretaking activities like feeding, bathing and changing nappies. Moreover, the primary attachment was often the father, sometimes the attachment was of equal strength for both parents (see table)

Useful teaching resource: Ainsworth: Attachment and the growth of love DVD - An excellent introduction to attachment theory, including footage from Mary Ainsworth's observations of mothers and infants in 1955.