Responding to Joint Attention Across the 6- Through 24-Month Age Period and Early Language Acquisition

This study examined individual differences in the development of the capacity of infants to respond to the joint attention bids of others (e.g., gaze shift, pointing, and vocalizing) across the first and second year. The primary aim of the study was to determine if responding to joint attention (RJA) in the first and second year was related to subsequent vocabulary acquisition and whether a specific period of development during the first 2 years was optimal for the assessment of individual differences in this skill. The study was also designed to determine if RJA provided unique predictive information about language development over and above that provided by parent reports of early vocabulary acquisition. Findings indicated that RJA at 6, 8, 10, 12, and 18 months was positively related to individual differences in vocabulary development. Furthermore, both a 6- to 18-month aggregate measure of RJA and a parent report measure of language development made unique contributions to the predictions of vocabulary acquisition. Finally, individual differences in RJA measured at 21 and 24 months were not related to language development.