A wide body of research has investigated the early cognitive and social-cognitive consequences of bilingualism, with mixed results. In some cases, bilingual children have been shown to attend more to social-pragmatic cues (e.g., eye gaze) than monolinguals (Brojde et al., 2012; Yow & Markman, 2011), especially when social-pragmatic cues conflict with lower-level perceptual cues (e.g., proximity). Because attention to social-pragmatic cues is important for language learning (Brooks & Meltzoff, 2005), this dissertation investigated differences in monolingual and bilingual two-year-olds’ attention to social-pragmatic cues, and how this attention related to language acquisition. This study used a novel approach of combining 1) an eye-tracking word learning paradigm, 2) live-action social tasks, and 3) parent-report measures of vocabulary development with a longitudinal design to measure changes in children’s attention to social-pragmatic cues related to vocabulary growth over a 6-month period.

Participants were observed at 24 months (T1) and 27 months (T2) of age. During each lab visit, participants first completed an eye-tracking word-learning task in which they saw videos of a model looking to one of two novel objects (visually salient or nonsalient) on a table and labeling it with a novel word. After these learning videos, participants were presented with three test trials that assessed their mapping of the novel word to the novel object. In addition to the eye-tracking task, participants completed three live-action social tasks that assessed their attention to an experimenter’s gaze cues. Also at T1 and T2, parents filled out MCDIs (a checklist of productive vocabulary) for their children; parents also completed follow-up MCDIs when their child was 30 months old (T3).

At T1, children’s performance on both the eye-tracking and the social tasks reflected difficulty attending to social cues in the presence of other conflicting information (e.g., salience). There were no reliable differences in performance between monolinguals and bilinguals. In the eye-tracking task, children did not show evidence of learning across test trials; rather, they looked longer to the salient object, regardless of whether it had been labeled in the learning videos. In the live-action tasks, children’s performance was at chance for most tasks. At T2, children showed more evidence of learning in the eye-tracking task, changing their looking across test trials when different object labels were used (e.g., looking more to the target object when the label from the learning videos was used and looking less to the target object when a different novel label was used). Children’s performance on the live-action tasks also improved relative to T1. Furthermore, vocabulary size at T2 was predicted by T1 eye-tracking and live-action task performance. At the time of writing, T3 vocabulary data were still being collected; future planned analyses are discussed.

In sum, this study showed that monolingual and bilingual infants attend similarly to information from social partners. Interestingly, the results also showed how easily infants’ attention could be drawn away from social cues, even though the 24-month-olds were experienced in engaging in joint attention with social partners. For both monolinguals and bilinguals, attention to social-pragmatic cues continues to be an important predictor of language development throughout the second year after birth.