This dissertation provides evidence of infants' and children's attention to the language and accent with which others speak in guiding their earliest social interactions, social judgments, and preferences among objects. In Part 1, 5-month-old infants were found to look longer at a person who previously spoke the infants' native language, compared to someone who previously spoke a foreign language. Infants similarly preferred speakers who spoke their native language with a native, rather than a foreign, accent; in contrast, infants did not look towards objects that had been paired with native speech. Early attention to the language others speak has social consequences, too, as evidenced by a further experiment in which 10-month-old infants reached selectively for toys offered by a native speaker rather than a foreign speaker.

Part 2 investigated the generality of infants' preference for native speakers, as well as the consequence of this preference for social learning. When tested with the same toy choice method as in Part 1, 10-month-old infants did not reach selectively for toys offered by own-race rather than other-race individuals. They did, however, reach for one of two toys that that was modeled, but not offered, by a speaker of their native language. Thus, language but not race guides infants' early preferences among interactions, providing evidence that all dimensions of social familiarity do not have equal social consequences.

Part 3 investigated the effect of speakers' language, accent, and race on older children's explicit social judgments. When presented with photographs and voice recordings of novel children, 5-year-old children indicated that they preferred to be friends with speakers of their native language rather than speakers of a foreign language or speakers with a foreign accent. These preferences were not due exclusively to relative intelligibility of the speech. Finally, children chose same-race children as friends when the target children were silent, but they chose other-race children with a native accent when accent was pitted against race. The results, discussed in an evolutionary framework, suggest that humans are predisposed to evaluate others along dimensions that distinguished neighboring social groups in prehistoric human societies.