Lexical effects on the phonetic categorization of speech: the role of acoustic structure.

This study examines the extent to which acoustic parameters contribute to lexical effects on the phonetic categorization of speech. Experiment 1 was designed to replicate previous findings. Two test continua were created varying in voice onset time. Results of both identification and reaction time (RT) range data showed an effect of lexical status at the phonetic boundary, but only in the slowest RT ranges, suggesting that lexical effects on phonetic categorization are postperceptual. Experiment 2 explored whether the lexical effect would emerge when the stimulus continua more nearly approximated the parameter values of natural speech. Both identification and RT range data indicated that the lexical effect disappeared. These results suggest that without attention to the acoustic structure of the stimuli, the role of top-down processing in phonetic categorization may be overemphasized.