They studied 60 babies from a working class area of Glasgow, observing them every four weeks for the first year and then again at 18 months.
Interviews were also conducted with the mothers, including questions about whom the infants smiled at, responded to and who caused them distress.
Naturalistic observation that resulted in 4 stages of attachment as a conclusion
Asocial (0-6 weeks): recognising + bonding with carers, treat human and non human objects similarly
Indiscriminate (2-7 months): develops social smile, prefer people over objects + recognise familiar adults but accepts comfort from any adult (no separation anxiety)
Specific (7 months): show separation anxiety to one adult + stranger anxiety, forms primary attachment figure and can crawl
Multiple (1 yr): secondary attachments form, then multiple attachments
Evaluation of Stages or attachment
+ Supported by cross cultural studies - Tronick described the infant care arrangements of the Efe people from Zaire, where children were cared for collectively. The children showed no signs of psychological effect, therefore the stages work for other cultures
X Individual differences in the way attachments are formed - may pass through stages at different rates because of reasons such as learning difficulties + neglect + abuse, but the stages assume the development is same for all infants. Therefore lacks validity