Schaffer and Emerson (1964) studied 60 babies from Glasgow at monthly intervals for the first 18 months of life using a
longitudinal method (Observations over a period of time).
Children were all studied in their own homes and visited monthly for approximately one year. Interactions with their carers were analysed to establish if and when infants started to display separation anxiety.
Results revealed that attachments were most likely to form with carers who were sensitive to the baby's signals, rather than the person they spent the most time with.
By 10 months old, most of the babies had several attachments, including attachments to mothers, fathers, siblings and extended family. It was observed that the mother was the main attachment figure for roughly half of the babies when they were 18 months old and the father for most of the others.