Perceptual adaptation to speaker characteristics: VOT boundaries in stop voicing categorization

Recent research suggests speech perception processes are flexible. For example, Norris et al. [Norris D, McQueen JM, & Cutler A (2003). Cognit. Psychol., 47, 204-238] demonstrated that listeners trained on stimuli containing ambiguous /s/-/f/ tokens subsequently showed an appropriate shift in their /s/-/f/ categorization boundaries based on the lexicality of the training stimuli. The present study extended this work by exploring changes in acoustic-phonetic criteria for stop category perception (voiced vs. voiceless) following brief exposure to sentence length stimuli. In a wordmonitoring task, native English listeners heard sentences produced by a native English speaker in which all syllableinitial /t/ and /d/ segments were digitally modified to be atypical of native English pronunciation, specifically, to have short-lag /t/s and prevoiced /d/s. Categorization of /t/ and /d/ was tested using a 5-token voice onset time (VOT) continuum prior to exposure and again following 20, 40, and 60 sentences. As predicted, listeners’ mean categorization boundary shifted to a shorter VOT after exposure to the modified speech. Results suggest listeners’ perceptual criteria for stop consonants can be adjusted to better match speakers’ productions. A follow-up experiment testing /g/-/k/ categorization with exposure to the same /t, d/-modified sentences did not show clear evidence for generalization to a different place of articulation.