Developmental and gender-related trends of intra-talker variability in consonant production.

This study investigates the effect of age and gender on the internal structure, cross-category distance, and discriminability of phonemic categories for two contrasts varying in fricative place of articulation (/s/-/∫/) and stop voicing (/b/-/p/) in word-initial tokens spoken by adults and normally developing children aged 9-14 yr. Vast between- and within-talker variability was observed with 16% of speakers exhibiting some degree of overlap between phonemic categories-a possible contribution to the range of talker intelligibility found in the literature. Females of all ages produced farther and thus more discriminable categories than males, although gender-marking for fricative between-category distance did not emerge until approximately 11 yr of age. Children produced farther yet also much more dispersed categories than adults with increasing discriminability with age, such that by age 13, children's categories were no less discriminable than those of adults. However, children's ages did not predict category distance or dispersion, indicating that convergence on adult-like category structure must occur later in adolescence.