Development of the voicing contrast: a comparison of voice onset time in stop preception and production

The acoustic cue voice onset time (VOT) was used to study development of the voicing contrast in 10 two-year-old children, 10 six-year-old children, and 20 adults. Thirty utterances of the words bees, peas, bear, pear, dime, time, goat, and coat were elicited from each subject, VOT measured, and individual production distributions for labial, apical, and velar stops plotted. Significant age-related differences were shown for mean VOT, mean lead time for voiced stops, range of the same words that were examined in the production portion of the investigation were obtained for these subjects from their judgments of synthetic speech stimuli. The relationship between identification and production was examined by assessing the degree of correspondence between the perception and production VOT values. Results of this analysis showed a developmental pattern of change primarily for the voiceless stops in the form of increased correspondence between perceptual identification categories and production VOT values. Three stages for acquisition of the voicing contrast related to VOT are indicated.