Schaffer + Emerson (1964) - researchers assessed separation anxiety by asking mothers questions about the kinds of protest the baby showed in 7 everyday separations e.g. mum leaving the room. Also stranger anxiety by the infants, anxiety response to unfamiliar adults adults. 60 babies, 31 males + 29 females, Glasgow from working-class, over 18 months, 1x month researchers would visit (Longitudinal).