Characterizing changes in parent labelling and gesturing and their relation to early communicative development.

In a longitudinal study, 17 parent-child dyads were observed during free-play when the children were 1;0, 1;6, and 2;0. Parents' labelling input in the verbal and gestural modalities was coded at each session, and parents completed a vocabulary checklist for their children at each visit. We analysed how the frequency of labelling in the verbal and gestural modalities changed across observation points and how changes in parental input related to children's vocabulary development. As a group, parents' verbal labelling remained constant across sessions, but gestural labelling declined at 2;0. However, there are notable individual differences in parental trajectories in both modalities. Parents whose verbal labelling frequency increased over time had children whose vocabulary grew more slowly than those whose labelling frequency decreased, remained constant, or peaked at 1;6. There were few systematic relations between patterns of parental gesturing and children's vocabulary development. Parents' verbal and gestural labelling patterns also appeared dissociable. However, parents' words and gestures were correlated when their children were 1;6, suggesting that gestures serve an important bootstrapping function at a critical point in children's vocabulary development.