Limitation: Research of Caregiver - infant interactions
P - difficult to interpret baby's behaviour
E - e.g hard to be sure if a baby's smiling or passing wind or a movement such as a hand twitch is due to sum random or a result of the care-giver's actions
E - these movements are just subtle changes in expression and small movements that may not mean anything signif as babies lack co-ord and most their bodies = immobile
L - cannot be certain that the behaviours seen have a spec meaning