Phonetic enhancement of sibilants in infant-directed speech.

The hypothesis that vocalic categories are enhanced in infant-directed speech (IDS) has received a great deal of attention and support. In contrast, work focusing on the acoustic implementation of consonantal categories has been scarce, and positive, negative, and null results have been reported. However, interpreting this mixed evidence is complicated by the facts that the definition of phonetic enhancement varies across articles, that small and heterogeneous groups have been studied across experiments, and further that the categories chosen are likely affected by other characteristics of IDS. Here, an analysis of the English sibilants /s/ and /[see text]/ in a large corpus of caregivers' speech to another adult and to their infant suggests that consonantal categories are indeed enhanced, even after controlling for typical IDS prosodic characteristics.