Do infants perceive word boundaries? An empirical study of the bootstrapping of lexical acquisition

Babies, like adults, hear mostly continuous speech. Unlike adults, however, they are not acquainted with the words that constitute the utterances; yet in order to construct representations for words, they have to retrieve them from the speech wave. Given the apparent lack of obvious cues to word boundaries (such as pauses between words), this is not a trivial problem. Among the several mechanisms that could be explored to solve this bootstrapping problem for lexical acquisition, a tentative but reasonable one posits the existence of some cues (other than silence) that signal word boundaries. In order to test this hypothesis, infants were used as informants in our experiments. It was hypothesized that if word boundary cues exist, and if infants are to use them in the course of language acquisition, then they should at least perceive these cues. As a consequence, infants should be able to discriminate sequences that contain a word boundary from those that do not. A number of bisyllabic stimuli were extracted either from within French words (e.g., mati in mathématicien), or from between words (e.g., mati in panorama typique). Three-day-old infants were tested with a non-nutritive sucking paradigm, and the results of two experiments suggest that infants can discriminate between items that contain a word boundary and items that do not. It is therefore conceivable that newborns are already sensitive to cues that correlate with word boundaries. This result lends plausibility to the hypothesis that infants might use word boundary cues during lexical acquisition.