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.

Developmental origins of the face inversion effect.

A hallmark of adults' expertise for faces is that they are better at recognizing, discriminating, and processing upright faces compared to inverted faces. We investigate the developmental origins of "the face inversion effect" by reviewing research on infants' perception of upright and inverted faces during the first year of life. We review the effects of inversion on infants' face preference, recognition, processing (holistic and second-order configural), and scanning as well as face-related neural responses. Particular attention is paid to the developmental patterns that emerge within and across these areas of face perception. We conclude that the developmental origins of the inversion effect begin in the first few months of life and grow stronger over the first year, culminating in effects that are commonly thought to indicate adult-like expertise. We posit that by the end of the first year, infants' face-processing system has become specialized to upright faces and a foundation for adults' upright-face expertise has been established. Developmental mechanisms that may facilitate the emergence of this upright-face specialization are discussed, including the roles that physical and social development may play in upright faces' becoming more meaningful to infants during the first year.