Learning the phonetic cues to the voiced-voiceless distinction: a comparison of child and adult speech perception

The present study explored children's perceptual capabilities with regard to the temporal acoustic cue of differential vowel duration, comparing children's perceptual identifications to those of adults. Three-year-old children, six-year-old children, and adults participated in two experiments, in which they were asked to identify (as voiced or voiceless) CVC words with uniformly voiceless final obstruents, but in which vowel duration was systematically varied. Children were also asked to identify a set of CONTROL stimuli, in which both closure voicing and vowel duration differences were present. Results indicate that both subject age and vowel duration of the TEST stimuli significantly affect identification responses. Adults and six-year olds evidence perceptual cross-over in their judgements for the TEST stimuli, while three-year-olds do not seem to change their identifications, regardless of variations in vowel duration. However, for both groups of children, the accuracy of identifications was greater for originally voiced stimuli on the CONTROL set of words, in which more than one potential cue to the voicing distinction was present. These results suggest that there is a complex and somewhat paradoxical relationship between developing production and perception which deserves further research. Children may consistently produce a phonetic difference (vowel duration) which they are unable to use as the SOLE perceptual cue for a phonological contrast.