Phonetic variability and prosodic structure in mothers

Spontaneous speech acoustics are highly variable. Such variability may be problematic for infants relying on phonological form to solve the segmentation problem. In the present study, acoustic measures of vowel duration and a computer model of speech segmentation were used to evaluate the problem of phonetic variability for a rhythm-based speech segmentation strategy. The specific questions under study were (1) whether or not mothers realized disyllabic vowel duration patterns consistently in spontaneous infant-directed speech, and (2) whether or not these patterns were distinctive enough in the context of an utterance to provide a useful cue for speech segmentation. Data from four English-speaking mothers indicated that the trochaic-like duration pattern may interact with phrase-position and with grammatical category, but when the resulting patterns are consistent, they provide useful segmentation cues for spontaneous infant-directed speech.