Development of rapid word-object associations in relation to expressive vocabulary: Shared commonalities in infants and toddlers with and without Williams syndrome.

Associative word learning, i.e., associating a word with an object, is an important building block of early word learning for TD infants. This study investigated the development of word-object associations by TD infants and infants and toddlers with Williams syndrome (WS), a rare genetic disorder associated with delayed language and cognitive development. The specific reasons for the language delays remain unknown. We investigated whether their early language delay could be related to differences in how word-object associations are formed. Fifty-nine 11- to 14-month-old TD infants and thirty-one 12- to 35-month-olds with WS were tested on a modified version of the "switch" task (Werker, Cohen, Lloyd, Casasola, & Stager, 1998) using phonetically dissimilar words and novel objects. Infants were classified as word learners or novice word learners based on their expressive vocabularies (greater than 10 words vs. 10 words or fewer). We found similar developmental patterns across both populations: Expressive vocabulary size classification was an important index of the development of word-object associations. Moreover, the development of word-object associations evidenced a domain-general progression from independent (processing objects separately from words) to integrated (processing associations between words and objects). As a group, word learners formed word-object associations, but novice word learners did not; instead, they focused primarily on the objects. Findings build on previous research suggesting that although early language acquisition is delayed in infants with WS, infants and toddlers with and without WS share a common developmental pattern and set of mechanisms in early word learning.