[The role of speech sound expectation in categorical perception (author's transl)]

The effects of specific hearer expectations on the categorical perception of speech sound continua were investigated. Subjects were asked to perform identification tests on synthetically produced /ba-da-ga/ continua. Hearer expectations for the /da/ category were raised and lowered, respectively, within the experimental group. Only the condition of raised expectation produced a change in the identification of the /da/ category: while the category boundaries themselves did not shift, the perception of /da/ sounds within these boundaries was significantly stabilized. Speech sound expectation apparently adapts to the structure provided by perceptual categories and thus contributes to an optimization of the perceptual process.