Responding to joint attention across the 6-through 24-month age period andearly language acquisition

This study examined individual differences in the development of the: capac ity 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 pri mary aim of the study was to determine if responding to joint attention (RJ A) in the first and second year was related to subsequent vocabulary acquis ition and whether a specific period of development during the first 2 years was optimal for the assessment of individual differences in this skill. Th e study was also designed to determine if RJA provided unique predictive in formation about language development over and above that provided by pal en t 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 me asure of RJA and a parent report measure of language development made uniqu e contributions to the predictions of vocabulary acquisition. Finally, indi vidual differences in RJA measured at 21 and 24 months were not related to language development.