While previous studies highlight the role that children’s interest in natural categories predicts their learning of new label-object associations in these categories, the long-term implications of such a relationship – the extent to which children’s interest shapes lexical development – remain unclear. The current study examines whether children’s interests in different natural object categories predict their subsequent interest and the number of words children know in those categories 6 months later. Using data from 67 children tested at 18 and 24 months of age, we found that parents’ estimates of interest in natural object categories at 18 months predicted their reports of their child’s interests at 24 months. Parent interest reports at 18 months also predicted the number of words that children are reported to know in that category at 24 months. Taken together, this study documents the longitudinal relationship between children’s interests, parents’ awareness of their children’s interests, and later vocabulary development.
