Minimum duration of reactivation at 3 months of age.

Briefly exposing subjects to an isolated component of an event after they have forgotten can reactivate their memory of it, leading to renewed retention on an ensuing test. In two experiments with forty-eight 3-month-old infants, we asked what minimum duration of a reactivation treatment could recover their forgotten memory of an operant mobile task and whether the minimum duration was affected by how long the memory was forgotten. In Experiment 1, the minimum duration for reactivating the memory 1 week after forgetting was 120 s-substantially longer than the minimum duration required for reactivation at 6 months after the same relative delay. In Experiment 2, the minimum effective duration for reactivation increased linearly with the time since forgetting, from 7.5 s after 1 day to 180 s after 3 weeks. This study reveals that the duration of an effective memory prime is directly related to age and to memory accessibility.