Reinstatement effects on retention at 3 months of age

In three experiments with 56 3-month-olds, we examined different numbers of reinstatements (reminders) on long-term retention. Infants learned to move a crib mobile by kicking and subsequently received one, two, or three reinstatements. Each reinstatement was a partial training episode one-sixth the duration of original training. Presenting a single reinstatement when the memory was inactive failed to recover it I day later (Experiment 1), but increasing the number of reinstatements when the memory was active to two (Experiment 2) and three (Experiment 3) progressively protracted retention. Although 3-month-olds typically remember for less than 6 days, after three reinstatements they still exhibited retention 6 weeks after training. Untrained controls who received an identical regimen of reinstatements exhibited no retention. These results demonstrate that periodic reinstatements can maintain young infants' retention over long delays and that the state of the memory at the time of reinstatement is critical to its effectiveness. (C) 1999 Academic Press.