During the 1970's, psychologist Mary Ainsworth further expanded upon Bowlby's groundbreaking work in her now-famous "Strange Situation" study. The study involved observing children between the ages of 12 to 18 months responding to a situation in which they were briefly left alone and then reunited with their mother (Ainsworth, 1978).
Based on these observations, Ainsworth concluded that there were three major styles of attachment: secure attachment, ambivalent-insecure attachment, and avoidant-insecure attachment. Researchers Main and Solomon (1986) added a fourth attachment style known as disorganized-insecure attachment. Numerous studies have supported Ainsworth's conclusions and additional research has revealed that these early attachment styles can help predict behaviours later in life.
Ainsworth and Wittig devised the strange situation to be able to test the nature of attachment systematically. The aim was to see how infants that were aged between 9 and 18 months behave under conditions of mild stress and also novelty. Stress is created in the strange situations by the presence of a stranger and by separation from a caregiver. This tests stranger anxiety and separation anxiety respectively. The strange situation also aims to encourage exploration by placing infants in a novel situation and thus tests the secure base concept.
The research room is a novel environment, a 9 x 9 foot square marked off into 16 squares to help in recording the infant's movements. The procedure consists of eight episodes, each designed to highlight certain behaviours. In the strange situation data is collected by a group of observers who record what the infant is doing every 15 seconds. The observer notes down which of the following behaviours is displaced and also scores the behaviour for intensity on a scale of 1 to 7.
Ainsworth et al combined the data from several studies, to make a total of 106 middle - class infants observed in