The Role of Sleep in Retention of New Words in Habitually and Non-Habitually Napping Children.

Daytime napping contributes to retention of new word learning in children. Importantly, children transition out of regular napping between ages 3-5 years, and the impact of this transition on memory is unclear. Here, we examined the performance of both non-habitually napping children (nap 0-3 days per week, = 28) and habitually napping children (nap 4-7 days per week, = 30) on a word learning task after a delay including either sleep or wakefulness. Children ages 3.5-4.5 years old experienced a brief exposure to two novel labels and their referents during training, a scenario that replicates learning experiences children encounter every day. After a 4-h delay, children were tested on the object-label associations. Using mixed effects logistic regression, we compared retention performance. Non-habitual nappers and habitual nappers displayed a different pattern of retention such that non-habitually napping children did equally well on a test of retention regardless of whether they napped or stayed awake during the delay. In contrast, habitually napping children needed a nap after learning to retain the novel object-label associations 4 h later. As a group, habitual nappers who remained awake after learning performed no better than chance on the retention test. As children transition out of naps, they may be less susceptible to interference and are better able to retain newly learned words across a delay including wakefulness.