Reinstatement maintains a memory in human infants for 1(1/2) years

This study tested the proposition of Campbell and Jaynes (1966) that reinstatement is the mechanism by which early memories are maintained over a significant period of development. In four progressive replications, 6-month-old human infants learned to move a miniature train around a track by lever-pressing. They received a brief reinstatement at 7, 8, 9, 12, and 18 months of age and a final retention test at 2 years of age. Although 6-month-olds usually remember this task for only 2 weeks, after five reinstatements they exhibited significant retention 1(1/2) years later. Untrained yoked controls that received the same reinstatement regimen exhibited no retention after any delay. These findings reveal that the immaturity of the brain at the time of encoding is not the rate-limiting step in whether infants remember over the long term. Rather, as long as infants periodically encounter a nonverbal reminder, they can maintain early memories over a significant period of development.