Ostensive and Referential Object Labeling Helps Infants Learn Generalizable Sound Patterns

Experience with one’s native language(s) alters the way that speech is perceived from early in infancy. The effects of language input are clearly illustrated in a development process termed phonetic attunement, where declines in perceiving non-native phonetic contrasts, and facilitation in perceiving native ones begin to emerge in the first year of life (Best, McRoberts, & Goodell, 2001; Kuhl et al., 2006; Werker & Tees, 1984), with phonetic development continuing into childhood (Walley & Flege, 1999). The goal of the present paper is to investigate the learning mechanisms responsible for phonetic attunement in the earliest stages of infancy. One proposed learning mechanism suggests that infants identify phonetic categories in a process termed distributional learning. Here, infants are assumed to identify phonetic categories by tracking the (Gaussian) frequency distributions of heard phonetic tokens in acoustic space (Maye & Gerken, 2000; McMurray, Aslin, & Toscano, 2009; Werker et al., 2007). Maye, Werker, & Gerken (2002) first reported developmental evidence for this hypothesis, showing that infant phonetic discrimination was affected by the distributional characteristics of speech input. However, recent work has challenged the notion that distributional learning alone can explain phonetic attunement (see Werker, Yeung, & Yoshida, 2012 for review). Additional cues could come from the rich environment in which speech is embedded such as, for example, the “social” nature of the environment in which infants receive speech input (Kuhl, Tsao, & Liu, 2003). An emerging body of work also suggests that the lexical context in which speech is heard may also provide a useful cue. For example, if phonetic tokens are consistently heard in distinct visual contexts (e.g., hearing “ball” in the context of a ball, and “doll” in the context of a doll), the perceptual distance between the two categories is increased for both adults and infants (Hayes-Harb, 2007; Yeung & Werker,