Listeners are maximally flexible in updating phonetic beliefs over time.

Perceptual learning serves as a mechanism for listenexrs to adapt to novel phonetic information. Distributional tracking theories posit that this adaptation occurs as a result of listeners accumulating talker-specific distributional information about the phonetic category in question (Kleinschmidt & Jaeger, 2015, Psychological Review, 122). What is not known is how listeners build these talker-specific distributions; that is, if they aggregate all information received over a certain time period, or if they rely more heavily upon the most recent information received and down-weight older, consolidated information. In the present experiment, listeners were exposed to four interleaved blocks of a lexical decision task and a phonetic categorization task in which the lexical decision blocks were designed to bias perception in opposite directions along a "s"-"sh" continuum. Listeners returned several days later and completed the identical task again. Evidence was consistent with listeners using a relatively short temporal window of integration at the individual session level. Namely, in each individual session, listeners' perception of a "s"-"sh" contrast was biased by the information in the immediately preceding lexical decision block, and there was no evidence that listeners summed their experience with the talker over the entire session. Similarly, the magnitude of the bias effect did not change between sessions, consistent with the idea that talker-specific information remains flexible, even after consolidation. In general, results suggest that listeners are maximally flexible when considering how to categorize speech from a novel talker.