MATURATIONAL INFLUENCES ON PERCEPTION OF CO-ARTICULATORY EFFECTS

Three experimental groups consisting of ten four-yr-olds, ten 11-year-olds, and ten adults were presented with tape-recorder voiceless stop+vowel syllables and subsyllabic segments isolated from the syllables by electronic gating. Subjects were instructed to identify each syllable. Comparisons of the performances of subjects in the three age groups permitted description of maturational influences on the ability to utilize coarticulatory cues in speech perception. The responses of the four-year-olds indicated that they were able to process coarticulatory information for the identification of consonants and vowels from subsyllabic segments. However, their ability to utilize these cues was more limited than that of 11-year-olds and adults. The four-year-old children experienced particular difficulty in the use of aperiodic information. The relative distribution of perceptual cues throughout the portions of the CV syllables was similar for all age groups. The overall phoneme identification accuracy levels of the 11-year-olds appeared to be established at an adult accuracy level. However, differences among all three age groups in regard to consistency of responses, markedness of substitution error preferences, and magnitude of the influence of acoustic stimulus duration on response accuracy suggest that strategies for estimation of phoneme identity may undergo further modification beyond the 11-year-old level before attaining the characteristics of the adult decoding process.