A second chance for a first impression: Lexically guided perceptual learning reflects cumulative experience with a talker's phonetic input

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Listeners use lexical knowledge to modify the mapping from acoustics to speech sounds, but the timecourse of experience that informs lexically guided perceptual learning (LGPL) is unknown. Some data suggest that learning depends on initial exposure to atypical productions, while other data suggest that learning reflects only the most recent exposure. Here we seek to reconcile these findings by assessing the type and timecourse of exposure that promote robust LGPL. In experiment 1, listeners were exposed to ambiguous fricatives embedded in either /s/- or /∫/-biasing contexts and then categorized items from an ashi-asi continuum at test. Learning was observed; the /s/-bias group showed more asi responses compared to the /∫/-bias group. In experiment 2, listeners heard both clear and ambiguous productions. Order and lexical bias were manipulated between-subjects, and perceptual learning occurred regardless of the order in which the productions were heard. In experiment 3, listeners heard both /s/- and /∫/-biased productions. Order differed between two exposure groups, and no difference between groups was observed at test. Moreover, the results showed a monotonic decrease in learning across experiments, in line with decreasing exposure to stable lexically biasing contexts, and were replicated across novel stimulus sets. The current results did not replicate previous findings showing that either initial or most recent experience are critical for LGPL. Rather, LGPL appears to reflect an aggregation of a talker's input over time.