Attention modulates perceptual learning of non-native-accented speech.

Listeners readily adapt to variation in non-native-accented speech, learning to disambiguate between talker-specific and accent-based variation. We asked (1) which linguistic and indexical features of the spoken utterance are relevant for this learning to occur and (2) whether task-driven attention to these features affects the extent to which learning generalizes to novel utterances and voices. In two experiments, listeners heard English sentences (Experiment 1) or words (Experiment 2) produced by Spanish-accented talkers during an exposure phase. Listeners' attention was directed to lexical content (transcription), indexical cues (talker identification), or both (transcription + talker identification). In Experiment 1, listeners' test transcription of novel English sentences spoken by Spanish-accented talkers showed generalized perceptual learning to previously unheard voices and utterances for all training conditions. In Experiment 2, generalized learning occurred only in the transcription + talker identification condition, suggesting that attention to both linguistic and indexical cues optimizes listeners' ability to distinguish between individual talker- and group-based variation, especially with the reduced availability of sentence-length prosodic information. Collectively, these findings highlight the role of attentional processes in the encoding of speech input and underscore the interdependency of indexical and lexical characteristics in spoken language processing.