Infant locomotion shapes proximity to adults during everyday play in the U.S.

Learning to walk expands infants' access to the physical environment and prompts changes in their communicative behaviors. However, little is known about whether walking also shapes infants' proximity to their adult social partners during everyday activities at home. Here we followed 89 infants (42 boys, 47 girls; 92% White, not Hispanic or Latino) longitudinally and documented connections between infant locomotion and infant-adult proximity on two timescales: (1) across developmental time, by comparing data from a session when infants could only crawl to a later session when they could walk (M walk onset = 12.15 months, range = 8-15); and (2) in real time, by testing whether the amount of time that infants spent in motion (regardless of their locomotor status) related to their interpersonal distance to adults. The developmental transition to walking corresponded to a significant, but modest, decrease in infant-adult proximity. Infants' moment-to-moment locomotion, however, was strongly related to patterns of interpersonal distance: infants who spent more time in motion spent less time near adults and instigated more proximity transitions, resulting in shorter and more dispersed bouts of proximity throughout sessions. Findings shed new light on how infants' motor achievements can reverberate across other domains of development, and how changes in infant development that researchers often observe over months arise from infants' moment-to-moment experiences.