Development of Infants' Preferential Looking Toward Native Language Speakers Across Distinct Social Contexts

Presenting pictures of faces side by side is a common paradigm to assess infants' attentional biases according to social categories, such as gender, race, and language. However, seeing static faces does not represent infants' typical experience of the social world, which involves people in motion and performing actions. Here, we assessed infants' looking preferences for native over foreign language speakers in two social contexts: the presentation of static faces and the presentation of people performing instrumental actions. In addition, we tested infants' preferential looking at 5 and 9 months of age to assess whether their pattern of preferential looking changes across development. The results of 5-month-old infants replicated and extended previous findings by showing that, at this age, infants typically look longer at people who previously spoke their native language. As found for other social categories such as race and gender, this familiarity-based looking preference was not evident at 9 months of age when infants were presented with static faces. However, when presented with more informative dynamic events, 9-month-old infants showed a temporally aligned preference for the native over the foreign language speaker. Specifically, infants' looking preference was time-locked to the completion of the action goal: when speakers grasped and lifted a toy. These results suggest potentially a familiarity-based preference toward native language speakers around 5 months of age, which may later develop into a more strategic selective response in service of information-seeking. Public Significance StatementThis study suggests that babies are prone to look at speakers of their native language over speakers of a foreign language. At 5 months of age, this tendency may be driven by a generic preference to look at people with more familiar attributes, but at 9 months, our results suggest infants go beyond generic preference and expect that the actions of native language speakers will carry more relevant information.