Listeners are initially flexible in updating phonetic beliefs over time

Abstract

Perceptual learning serves as a mechanism for listeners 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, Psychological Review, 122, 148–203, 2015). 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 of a “s”–“sh” contrast. Listeners returned several days later and completed the identical task again. In each individual session, listener’s perception of a “s”–“sh” contrast was biased by the information in the immediately preceding lexical decision block (though only when participants heard the “sh”-biasing block first, which was likely driven by stimulus characteristics). There was evidence that listeners accrued information about the talker over time since the bias effect diminished in the second session. In general, results suggest that listeners initially maintain some flexibility with their talker-specific phonetic representations, but over the course of several exposures begin to consolidate these representations.