The functions of acoustic-phonetic modifications in infant-directed speech (IDS) remain a question: do they specifically serve to facilitate language learning via enhanced phonemic contrasts (the hyperarticulation hypothesis) or primarily to improve communication via prosodic exaggeration (the prosodic hypothesis)? The study of lexical tones provides a unique opportunity to shed light on this, as lexical tones are phonemically contrastive, yet their primary cue, pitch, is also a prosodic cue. This study investigated Cantonese IDS and found increased intra-talker variation of lexical tones, which more likely posed a challenge to rather than facilitated phonetic learning. Although tonal space was expanded which could facilitate phonetic learning, its expansion was a function of overall intonational modifications. Similar findings were observed in speech to pets who should not benefit from larger phonemic distinction. We conclude that lexical-tone adjustments in IDS mainly serve to broadly enhance communication rather than specifically increase phonemic contrast for learners.
The acoustic properties of infant-directed speech (IDS) have been widely studied, but whether and how young learners’ language development benefits from individual properties remains to be confirmed. This study investigated whether toddlers’ word processing was affected by tone hyperarticulation in the IDS of a tone language. Nineteen- and 23-month-old Cantonese-learning toddlers completed a familiar word recognition task and were tested (a) in the hyperarticulated-tone (HT) condition in which the tonal distances were exaggerated, and (b) in the non-hyperarticulated-tone (NT) condition with smaller tonal distances that resembled those in adult-directed speech. The 19-month-old toddlers performed significantly better in the HT condition than in the NT condition, while the 23-month-olds performed comparably well in both conditions. These findings suggest that tone language learners’ word recognition can be facilitated by tone hyperarticulation in IDS, in the middle of the second year of life; as their language development proceeds, this facilitatory effect appears to largely diminish by the end of the second year of life.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.