Schaffer and Emerson method
Adopting a longitudinal design
Studied 60 infants (31 males, 29 female) from Glaswegian working class families
They visited the baby and mother every month for the first year and again at 18 months
The mothers were asked questions about the kind of behaviour their babies showed during several everyday separation episodes (eg adult leaving room separation anxiety)
They also assessed stranger anxiety (the infants anxiety response to unfamiliar adults)
These behaviours were used to assess the development of the infant's attachment