Voice Onset Time in Infant-directed Speech at Two Ages
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Studies have reported differences between infant-directed speech (IDS) and adult-directed speech (ADS), suggesting that mothers adjust speech to their infants in ways that may help children process the incoming acoustical signal. One aspect of IDS that has been examined is clarification of voice onset time (VOT). Results have been inconsistent and many studies only report differences in VOT values rather than differences in amount of overlap between voiced and voiceless items. The present study examines 15 mothers' VOT in IDS at 7.5 months old and again at 11 months as compared to their VOT values in ADS. Words with initial stop consonants that occurred in IDS and ADS conditions were analyzed using PRAAT. Contrary to hypotheses, results show that VOT in IDS was less differentiated than VOT in ADS. Additionally, voiced items had significantly longer VOT in IDS than ADS, with no difference for voiceless items. Possible explanations are discussed.