Infants' Sleep Supports the Emergence and Mastery of Locomotor and Linguistic Skills.

Infant sleep is disrupted around the onset of motor milestones, but the causal mechanisms underlying this relationship are unclear. This study aims to corroborate prior reports of the link between locomotor milestone onset and sleep disruptions and expand the literature by asking whether language milestones are also associated with sleep disruptions. Time-series changepoint detection analyzed parent reported milestone onset data and sleep data of two age cohorts collected remotely through an online app and baby monitor system. Disruptions to sleep were found relative to the onsets of first crawling steps, first walking steps, walking mastery, babbling, cooing, expressive jargon, new word use, and object labeling. These results replicate evidence for a relationship between sleep disruption and locomotor milestone onset and offer the first evidence of disruptions to sleep associated with language milestones. To our knowledge this is the first study to show that skill acquisition affects infants' sleep prior to the expression of the skill. Changes in sleep patterns demonstrate that prior to skill onset skill-relevant behaviors are marshaled and coordinated to facilitate the emergence of new skills. After skill onset, sleep functions to consolidate new knowledge and skills and support the process of mastery.