Developmental changes in the speed of social attention in early word learning

How do children learn words so rapidly? A powerful source of information about a new word’s meaning is the set of social cues provided by its speaker (e.g. eye-gaze). Studies of children’s use of social cues have tended to focus on the emergence of this ability in early infancy. We show, however, that this early-emerging ability has a long developmental trajectory: Slow, continuous improvements in speed of social information processing occur over the course of the first five years of life. This developing ability to allocate social attention is a significant bottleneck on early word learning—continuous changes in social information processing predict continuous changes in children’s ability to learn new words. Further, we show that this bottleneck generalizes to children diagnosed with autism spectrum disorder, whose social information processing is atypical. These results describe a route by which increases in social expertise can lead to changes in language learning ability, and more generally highlight the dependence of developmental outcomes not on just the existence of particular competencies, but on their proficient use in complex contexts.