Longitudinal Relations between Independent Walking, Body Position, and Object Experiences in Home Life

How do age and the acquisition of independent walking relate to changes in infants' everyday experiences? We used a novel ecological momentary assessment (EMA) method to gather caregiver reports of infants' restraint, body position, and object holding via text messages sparsely sampled across multiple days of home life at 10, 11, 12, and 13 months of age. Using data from over 4,000 EMA samples from N = 62 infants recruited from across the United States and sampled longitudinally, we measured changes in the base rates of different activities in daily life. With age, infants spent more time unrestrained. With the onset of walking, infants spent less time sitting and prone and more time upright. Although rates of object holding did not change with age or walking ability, we found that infants who can walk hold objects more often in an upright position compared with nonwalkers. We discuss how accurately measuring changes in lived experiences serves to constrain theories about developmental mechanisms.