Spoken language is characterized by an enormous amount of variability in how linguistic segments are realized. In order to investigate how speech perceptual processes accommodate to multiple sources of variation, adult native speakers of American English were trained with English words or sentences produced by six Spanish-accented talkers. At test, listeners transcribed utterances produced by six familiar or unfamiliar Spanish-accented talkers. With only brief exposure, listeners perceptually adapted to accent-general regularities in spoken language, generalizing to novel accented words and sentences produced by unfamiliar accented speakers. Acoustic properties of vowel production and their relation to identification performance were assessed to determine if the English listeners were sensitive to systematic variation in the realization of accented vowels. Vowels that showed the most improvement after Spanish-accented training were distinct from nearby vowels in terms of their acoustic characteristics. These findings suggest that the speech perceptual system dynamically adjusts to the acoustic consequences of changes in talker's voice and accent.

Foreign-accented speech contains multiple sources of variation that listeners learn to accommodate. Extending previous findings showing that exposure to high-variation training facilitates perceptual learning of accented speech, the current study examines to what extent the structure of training materials affects learning. During training, native adult speakers of American English transcribed sentences spoken in English by native Spanish-speaking adults. In Experiment 1, training stimuli were blocked by speaker, sentence, or randomized with respect to speaker and sentence (Variable training). At test, listeners transcribed novel English sentences produced by Spanish-accented speakers. Listeners’ transcription accuracy was highest in the Variable condition, suggesting that varying both speaker identity and sentence across training trials enabled listeners to generalize their learning to novel speakers and linguistic content. Experiment 2 assessed the extent to which ordering of training tokens by a single factor, speaker intelligibility, would facilitate speaker-independent accent learning, finding that listeners’ test performance did not reliably differ across conditions. Overall, these results suggest that the structure of training exposure, specifically trial-by-trial variation on both speaker’s voice and linguistic content, facilitates learning of the systematic properties of accented speech. The current findings suggest a crucial role of training structure in optimizing perceptual learning. Beyond characterizing the types of variation listeners encode in their representations of spoken utterances, theories of spoken language processing should incorporate the role of training structure in learning lawful variation in speech.

The current study examined the effects of talker-specific perceptual learning on the time course of spoken word processing to assess the point at which effects of talker familiarity emerge during spoken word recognition. Listeners learned to identify six talkers’ voices (three males, three females) over three days of training. At test, listeners either completed an immediate or a delayed word-shadowing task. Items at test were novel words produced by the six familiar talkers heard during training and by a set of six unfamiliar talkers. A separate group of controls completed the test phase only. The results indicated that effects of talker familiarity were found in both the immediate and delayed shadowing tasks. Listeners were faster to shadow words produced by familiar than unfamiliar talkers both when responding immediately to the word and when responding after a cued delay. When tested with unfamiliar talkers, the trained listeners did not differ from untrained controls. These findings suggest that effects of talker familiarity emerge relatively early in spoken word processing and persist as word recognition unfolds. Perceptual learning of talker-specific characteristics appears to influence the time course of lexical processing by facilitating the rapid recovery of the linguistic structure of spoken words.

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The present study investigated the relative contribution of talker-specific and accent-general learning to the perceptual adaptation of accented speech. Adult native English-speaking listeners were asked to transcribe Korean-accented English words in a brief, high variability perceptual learning paradigm. During training, listeners transcribed individual words produced by six Korean-accented speakers and were given feedback on their transcription performance. Controls were either trained with native English speakers or were given no training. At test, listeners were presented with Korean-accented speech produced by both familiar and unfamiliar talkers. The results suggest that listeners learned accent-general properties of nonnative speech. Listeners showed better transcription performance for both familiar and unfamiliar accented talkers relative to English and no training controls. However, talker-specific properties such as individual talker familiarity and baseline intelligibility also influenced transcription performance at test. These findings suggest that although listeners are sensitive to multiple sources of variation in speech, they appear to engage in accent-general perceptual adaptation to non-native speech.