The role of distributional information in cross-talker generalization of phonetic category retuning

Abstract

Listeners use lexical information to retune phoneme categories. Previous findings on the specificity of such perceptual adjustments suggest that cross-talker generalization occurs when talkers are acoustically similar. An alternative mechanism implies that listeners are sensitive to the statistical distribution of phonetic variation across speakers and can use this sensitivity to track both group- and talker-specific phoneme boundaries. Our objective is to disambiguate between these two possibilities. In the experiment, listeners hear words with an ambiguous fricative produced by multiple speakers of American English. Utterances across talkers vary in two ways: 1) the similarity of particular talkers’ categorization curves and 2) the statistical distribution of sounds along the phonetic continuum (e.g., unimodal vs. bimodal) across talkers. We assess phonetic category retuning using novel words by novel talkers whose utterances either match or mismatch talker-specific properties or the distribution of phonetic realizations heard during exposure. If cross-talker generalization is similarity-based, listeners should generalize retuned phonetic representations to specific similar-sounding talkers at test. Alternatively, if listeners capitalize on the statistical distribution of exposure sounds, listeners should generalize to test talkers whose productions are consistent with the learned distribution. Results inform the conditions under which listeners form talker-independent representations of speech sound categories.