Abstract:

One class of phonetic context effects involves durational contrasts: A signal can be perceived as a stop consonant or a glide, depending on the length of the adjacent segment. For example, the syllable [wa] is perceived as [ba] if the steady-state frequencies corresponding to the vowel are lengthened. Thus the vocalic information affects reported phonetic judgments of the prior consonantal segment. The neural model presented processes consonant--vowel transitions and steady-state vowel signals by transient and sustained channels. This model predicts the experimental effects of vowel duration, CV transition rate, and frequency extent in identifying [ba] and [wa]. The product of a leaky integrator's output with the quotient of two linear expressions in the stimulus parameters generates the model's output. With a single small set of parameters, the model predicts over 99% of the variance in two data sets [J. L. Miller and A. M. Liberman, Percept. Psychophys. 25(6), 457--465 (1979); Schwab et al., Percept. Psychophys. 29(2), 121--128 (1981)]. It outperforms a number of simple alternative models. Implications for other phonetic distinctions and physiological analogs to the model in monkey cortex are described. [Work supported by AFOSR and ONR.]