What do mothers' child-directed Cantonese tone productions tell us about the function of child-directed speech?

Abstract

The role of child-directed speech has been debated for over decades. Two hypotheses – the hyperarticulation hypothesis and the pragmatic hypothesis --have been proposed to explain the speech characteristics found in child-directed speech. Pitch is used in tone languages for both phonemic distinctions and pragmatic functions. We tested the two hypotheses by examining the perceptual accuracy and acoustic properties of child-directed lexical tones. The results showed that mothers acoustically modified their tones when speaking to young children. However, there was little evidence that mothers hyperarticulated the more confusing tones. The acoustic modifications followed prosodic effects on tone productions. Surprisingly, mother produced the tones in child-directed speech with significantly lower perceptual accuracy than in adult-directed speech. Taken together, the findings rejected the hyperarticulation hypothesis and supported the pragmatic hypothesis.