Evaluation points of the validity of Schaffer and Emerson's (1964) study into interactional synchrony.

. - internal validity: mothers might be more/less sensitive to infant's protests so may report higher/lower distress . + ecological validity: research conducted in homes and infants don't recognise they're being recorded so don't respond to demand characteristics and reactions would e mostly reflective of real life . - temporal validity: in '64 women = stay at home etc. now they work more + paternity leave means that the %'s of the main attachment figures may be different . - population validity: Sagi et al (1994) found that multiple attachments were more common/didn't have as close relationship with birth mother in collectivist societies