Memory for complex dynamic events across two weeks in early infancy

Results from recent studies have shown that infants down to six months of age remember complex dynamic events across a two-week retention interval. However, the earliest age at which such material can be remembered is unknown. To explore this gap, the present study examined infants' memory for complex dynamic events after a delay of two weeks in a visual paired-comparison design. We tested two age groups, a group of six-month-olds (N=37) and a group of four-month-olds (N=37). At T₁ participants saw one of two animated movies with a simple narrative. At T₂ infants saw both movies simultaneously and visual preference was discerned with eye-tracking. The six-month-olds looked reliably longer at the familiar movie thus indicating memory for this movie while the looking-pattern of the four-month-olds did not differ from chance. Supplementary Bayesian analyses showed moderate evidence for the six-month-olds looking more at the familiar movie than chance while showing moderate evidence for the 4-month-olds looking at chance level. These findings replicate recent findings with identical stimuli for the six-month-olds but fail to demonstrate memory in the group of 4-month-olds. Different analytical approaches are discussed as well as the implications of the results in relation to visual-paired comparison studies in general and the development of event memory in particular.