Nap-dependent declarative memory consolidation in 12-month-old infants – A conceptual replication study

The aim of this study was to replicate and extend previous findings on sleep-dependent declarative memory consolidation in infants. Fifty-one 12-month-old infants were randomly assigned to one of three conditions: nap (n = 18), wake (n = 17), or baseline control (n = 16). Declarative memory performance was assessed via deferred imitation paradigms. After observing demonstrations of target actions on an activity board, infants in the nap condition took a naturally occurring nap, whereas infants in the wake condition remained awake for a matched period. Afterwards, infants had the opportunity to imitate the target actions during the test session. The delay between demonstrations and test was 149 min, on average. Post-encoding sleep was measured using polysomnography in the nap condition. Infants in the nap condition slept for 67 min on average. Only infants in the nap condition showed retention for the target actions after the delay. The findings confirm the critical role of post-learning naps in consolidating declarative memories in infants, and demonstrate that this effect applies to different types of learning materials.