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.

Effects of lexical frequency on the post-exposure magnitude of recalibration in lexically guided perceptual learning: An explorative analysis.

Listeners use lexical information to guide the mapping between acoustic signals and representations of speech sound. This process is known as perceptual learning and results in recalibration of phonetic categories. The current work examines the effect of lexical frequency of exposure words on the magnitude of recalibration. Results showed comparable levels of perceptual learning for listeners exposed to high-frequency vs low-frequency critical words, in line with empirical findings that suggest that if frequency affects recalibration, such effects may be difficult to detect. These findings warrant further empirical probing and theoretical characterization of the role of lexical frequency in perceptual learning.

A second chance for a first impression: Sensitivity to cumulative input statistics for lexically guided perceptual learning.

Listeners use lexical knowledge to modify the mapping from acoustics to speech sounds, but the timecourse of experience that informs lexically guided perceptual learning is unknown. Some data suggest that learning is contingent 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 lexcially guided perceptual learning. In three experiments, listeners (n = 560) heard 20 critical productions interspersed among 200 trials during an exposure phase and then categorized items from an ashi-asi continuum in a test phase. In Experiment 1, critical productions consisted of ambiguous fricatives embedded in either /s/- or /ʃ/-biasing contexts. Learning was observed; the /s/-bias group showed more asi responses compared to the /ʃ/-bias group. In Experiment 2, listeners heard ambiguous and clear productions in a consistent context. Order and lexical bias were manipulated between-subjects, and perceptual learning occurred regardless of the order in which the clear and ambiguous productions were heard. In Experiment 3, listeners heard ambiguous fricatives in both /s/- and /ʃ/-biasing contexts. 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. In contrast to previous findings showing that either initial or most recent experience are critical for lexically guided perceptual learning, the current results suggest that perceptual learning reflects cumulative experience with a talker's input over time.

Communicative Context Affects Use of Referential Prosody.

The current study assessed the extent to which the use of referential prosody varies with communicative demand. Speaker-listener dyads completed a referential communication task during which speakers attempted to indicate one of two color swatches (one bright, one dark) to listeners. Speakers' bright sentences were reliably higher pitched than dark sentences for ambiguous (e.g., bright red versus dark red) but not unambiguous (e.g., bright red versus dark purple) trials, suggesting that speakers produced meaningful acoustic cues to brightness when the accompanying linguistic content was underspecified (e.g., "Can you get the red one?"). Listening partners reliably chose the correct corresponding swatch for ambiguous trials when lexical information was insufficient to identify the target, suggesting that listeners recruited prosody to resolve lexical ambiguity. Prosody can thus be conceptualized as a type of vocal gesture that can be recruited to resolve referential ambiguity when there is communicative demand to do so.

Developmental change in children's sensitivity to sound symbolism.

The current study examined developmental change in children's sensitivity to sound symbolism. Three-, five-, and seven-year-old children heard sound symbolic novel words and foreign words meaning round and pointy and chose which of two pictures (one round and one pointy) best corresponded to each word they heard. Task performance varied as a function of both word type and age group such that accuracy was greater for novel words than for foreign words, and task performance increased with age for both word types. For novel words, children in all age groups reliably chose the correct corresponding picture. For foreign words, 3-year-olds showed chance performance, whereas 5- and 7-year-olds showed reliably above-chance performance. Results suggest increased sensitivity to sound symbolic cues with development and imply that although sensitivity to sound symbolism may be available early and facilitate children's word-referent mappings, sensitivity to subtler sound symbolic cues requires greater language experience.

The Specificity of Sound Symbolic Correspondences in Spoken Language.

Although language has long been regarded as a primarily arbitrary system, sound symbolism, or non-arbitrary correspondences between the sound of a word and its meaning, also exists in natural language. Previous research suggests that listeners are sensitive to sound symbolism. However, little is known about the specificity of these mappings. This study investigated whether sound symbolic properties correspond to specific meanings, or whether these properties generalize across semantic dimensions. In three experiments, native English-speaking adults heard sound symbolic foreign words for dimensional adjective pairs (big/small, round/pointy, fast/slow, moving/still) and for each foreign word, selected a translation among English antonyms that either matched or mismatched with the correct meaning dimension. Listeners agreed more reliably on the English translation for matched relative to mismatched dimensions, though reliable cross-dimensional mappings did occur. These findings suggest that although sound symbolic properties generalize to meanings that may share overlapping semantic features, sound symbolic mappings offer semantic specificity.

The role of training structure in perceptual learning of accented speech.

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 unfamiliar 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 from that in the no-training control condition. Overall, these results suggest that the structure of training exposure, specifically trial-to-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. (PsycINFO Database Record