Generalizing without Encoding Specifics: Infants Infer Phonotactic Patterns on Sound Classes

In the study of language acquisition, a key question involves the representations that infants use while processing speech and learning phonology. Precise representations for specific sounds are crucial when the infant starts putting together a lexicon, since minimal distinctions can cue differences in meaning. In the process of language acquisition, infants must also learn constraints on the position and sequencing of sounds, that is, the phonotactics. Many if not most phonological patterns concern sets of sounds that share phonetic and phonological characteristics, rather than individual sounds or groups of completely unrelated sounds (Mielke, 2008). For instance, in German and Russian, all final stops and fricatives are voiceless; but in no language is it the case that only some stops and some fricatives are voiceless word-finally, whereas the others are voiced. Based on such generalizations, phonological theory has often assumed that learners can represent phonotactic patterns directly in terms of the natural class, for example through the phonological features that are shared between all the members of the class and no non-member (Chomsky and Halle, 1968; Hall, 2001). In psycholinguistic terms, representing phonotactic patterns at the level of the sound class may be particularly advantageous, as this allows both a more parsimonious description and the generalization to unobserved cases. In this paper, we assess whether infants’ early representations of phonotactic patterns are based on sound classes, or whether class-based representations are derived from sound-based constraints. A growing literature using artificial grammar paradigms strongly suggests that young infants can encode patterns on sound classes (a recent summary in Cristia et al., 2011a). In these studies, infants are first exposed to a phonological pattern in a subset of a natural class, and subsequently tested with the pattern instantiated