Moving through everyday life: distinct developmental timescales for head-rotation magnitude and rotation efficiency in infancy

Infants actively shape their experience through self-generated movement. They need to move their head efficiently to explore and interact with their environment and to hold their head still to sustain attention. Controlled laboratory studies have documented the importance of head movements in orienting and stabilizing infant visual attention, but little is known about how head control develops as infants go about daily life, the setting in which development actually unfolds. We analyzed 383 hours of egocentric video collected from 88 infants aged 3 weeks to 29 months using head-mounted cameras in infants homes. Using a visual-odometry algorithm, we quantified rotational magnitude, the size of head movements; and rotational efficiency, the directional coherence of head movements. Head-rotation magnitude increased across the first year, and rotational efficiency improved throughout development.