The role of CDS : an acoustic and perceptual examination of child-directed and adult-directed Cantonese tone production

Abstract

The role of child-directed speech has been debated for over decades. Two hypotheses – the Didactic Hypothesis and the Affect Hypothesis – have been proposed to explain the speech characteristics found in child-directed speech. This study aimed to test these two hypotheses using perceptual and acoustic analyses of mothers’ child-directed and adult-directed Cantonese tone productions. Mothers of the sixty-two Cantonese-speaking children aged one to five years produced 36 familiar and unfamiliar words in isolation and in sentence-final position to their children and to an adult. No significant difference was found in perceptual accuracy between adult-directed and child-directed speech. Acoustic analyses revealed that child-directed speech were produced with significant higher pitch and longer duration than adult-directed speech. No systematic acoustic differences were found in the contrastive cues between easily confusing tone pairs. Both perceptual and acoustic characteristics of sentence-final prosodic effect appeared to mirror the patterns observed in child-directed speech. The findings indicated that the acoustic differences in child-directed tone did not enhance the tone contrasts among the tones and, therefore, rejected the hypothesis that pitch modifications in child-directed tones were used for didactic purposes. Affect Hypothesis was suggested as an alternative.