Ontogeny of index-finger pointing.

Index-finger pointing is foundational to language acquisition. Less is known about its emergence. In lab-based monthly longitudinal assessments from 8-13 months (N = 31) the study measured longitudinal predictors of index-finger pointing: parent pointing and infants' earlier emerging showing, hand-pointing, and point-following. All behaviors increased significantly with age and showed inter-individual stability. At 11 months all behaviors except hand pointing were synchronously interrelated, with no evidence for an earlier synchronous interrelation between behaviors. Caregiver pointing and infants' earlier behaviors longitudinally predicted the age of emergence of index-finger pointing. An additional cross-sectional comparison of parent pointing at 5 and 7 months (N = 44) showed that significantly fewer caregivers of 5- compared to 7-month-olds pointed for their infants. Findings suggest that pointing emerges as an outcome of social co-construction across the first year of life.