The role of temporal and dynamic signal components in the perception of syllable-final stop voicing by children and adults

Adults whose native languages permit syllable-final obstruents, and show a vocalic length distinction based on the voicing of those obstruents, consistently weight vocalic duration strongly in their perceptual decisions about the voicing of final stops, at least in laboratory studies using synthetic speech. Children, on the other hand, generally disregard such signal properties in their speech perception, favoring formant transitions instead. These age-related differences led to the prediction that children learning English as a native language would weight vocalic duration less than adults, but weight syllable-final transitions more in decisions of final-consonant voicing. This study tested that prediction. In the first experiment, adults and children (eight and six years olds) labeled synthetic and natural CVC words with voiced or voiceless stops in final C position. Predictions were strictly supported for synthetic stimuli only. With natural stimuli it appeared that adults and children alike weighted syllable-offset transitions strongly in their voicing decisions. The predicted age-related difference in the weighting of vocalic duration was seen for these natural stimuli almost exclusively when syllable-final transitions signaled a voiced final stop. A second experiment with adults and children (seven and five years old) replicated these results for natural stimuli with four new sets of natural stimuli. It was concluded that acoustic properties other than vocalic duration might play more important roles in voicing decisions for final stops than commonly asserted, sometimes even taking precedence over vocalic duration.