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1. Right Posterior Temporal Cortex Supports Integration of Phonetic and Talker Information

   https://doi.org/10.1162/nol_a_00091  

   Luthra, Sahil; Magnuson, James S.; Myers, Emily B. (March 2023, Neurobiology of Language)

   Abstract Though the right hemisphere has been implicated in talker processing, it is thought to play a minimal role in phonetic processing, at least relative to the left hemisphere. Recent evidence suggests that the right posterior temporal cortex may support learning of phonetic variation associated with a specific talker. In the current study, listeners heard a male talker and a female talker, one of whom produced an ambiguous fricative in /s/-biased lexical contexts (e.g., epi?ode) and one who produced it in /∫/-biased contexts (e.g., friend?ip). Listeners in a behavioral experiment (Experiment 1) showed evidence of lexically guided perceptual learning, categorizing ambiguous fricatives in line with their previous experience. Listeners in an fMRI experiment (Experiment 2) showed differential phonetic categorization as a function of talker, allowing for an investigation of the neural basis of talker-specific phonetic processing, though they did not exhibit perceptual learning (likely due to characteristics of our in-scanner headphones). Searchlight analyses revealed that the patterns of activation in the right superior temporal sulcus (STS) contained information about who was talking and what phoneme they produced. We take this as evidence that talker information and phonetic information are integrated in the right STS. Functional connectivity analyses suggested that the process of conditioning phonetic identity on talker information depends on the coordinated activity of a left-lateralized phonetic processing system and a right-lateralized talker processing system. Overall, these results clarify the mechanisms through which the right hemisphere supports talker-specific phonetic processing. 

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2. Perceptual Cue Weighting Is Influenced by the Listener's Gender and Subjective Evaluations of the Speaker: The Case of English Stop Voicing

   https://doi.org/10.3389/fpsyg.2022.840291  

   Yu, Alan C. (April 2022, Frontiers in Psychology)

   Speech categories are defined by multiple acoustic dimensions and their boundaries are generally fuzzy and ambiguous in part because listeners often give differential weighting to these cue dimensions during phonetic categorization. This study explored how a listener's perception of a speaker's socio-indexical and personality characteristics influences the listener's perceptual cue weighting. In a matched-guise study, three groups of listeners classified a series of gender-neutral /b/-/p/ continua that vary in VOT and F0 at the onset of the following vowel. Listeners were assigned to one of three prompt conditions (i.e., a visually male talker, a visually female talker, or audio-only) and rated the talker in terms of vocal (and facial, in the visual prompt conditions) gender prototypicality, attractiveness, friendliness, confidence, trustworthiness, and gayness. Male listeners and listeners who saw a male face showed less reliance on VOT compared to listeners in the other conditions. Listeners' visual evaluation of the talker also affected their weighting of VOT and onset F0 cues, although the effects of facial impressions differ depending on the gender of the listener. The results demonstrate that individual differences in perceptual cue weighting are modulated by the listener's gender and his/her subjective evaluation of the talker. These findings lend support for exemplar-based models of speech perception and production where socio-indexical features are encoded as a part of the episodic traces in the listeners' mental lexicon. This study also shed light on the relationship between individual variation in cue weighting and community-level sound change by demonstrating that VOT and onset F0 co-variation in North American English has acquired a certain degree of socio-indexical significance. 

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3. Compensation for coarticulation despite a midway speaker change: Reassessing effects and implications

   https://doi.org/10.1371/journal.pone.0291992  

   Viswanathan, Navin; Rinzler, Ana; Kelty-Stephen, Damian G (January 2024, PLOS ONE)

   Cavicchio, Federica (Ed.)

   Accounts of speech perception disagree on how listeners demonstrate perceptual constancy despite considerable variation in the speech signal due to speakers’ coarticulation. According to the spectral contrast account, listeners’ compensation for coarticulation (CfC) results from listeners perceiving the target-segment frequencies differently depending on the contrastive effects exerted by the preceding sound’s frequencies. In this study, we reexamine a notable finding that listeners apparently demonstrate perceptual adjustments to coarticulation even when the identity of the speaker (i.e., the “source”) changes midway between speech segments. We evaluated these apparent across-talker CfC effects on the rationale that such adjustments to coarticulation would likely be maladaptive for perceiving speech in multi-talker settings. In addition, we evaluated whether such cross-talker adaptations, if detected, were modulated by prior experience. We did so by manipulating the exposure phase of three groups of listeners by (a) merely exposing them to our stimuli (b) explicitly alerting them to talker change or (c) implicitly alerting them to this change. All groups then completed identical test blocks in which we assessed their CfC patterns in within- and across-talker conditions. Our results uniformly demonstrated that, while all three groups showed robust CfC shifts in the within-talker conditions, no such shifts were detected in the across-talker condition. Our results call into question a speaker-neutral explanation for CfC. Broadly, this demonstrates the need to carefully examine the perceptual demands placed on listeners in constrained experimental tasks and to evaluate whether the accounts that derive from such settings scale up to the demands of real-world listening. 

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4. Apparent-time variation in the use of multiple cues for perception of anticipatory nasal coarticulation in California English

   https://doi.org/10.16995/glossa.10831  

   Zellou, Georgia; Cohn, Michelle (January 2024, Glossa: a journal of general linguistics)

   This study examines apparent-time variation in the use of multiple acoustic cues present on coarticulatorily nasalized vowels in California English. Eighty-nine listeners ranging in age from 18-58 (grouped into 3 apparent-time categories based on year of birth) performed lexical identifications on syllables excised from words with oral and nasal codas from six speakers who produced either minimal (n=3) or extensive (n=3) anticipatory nasal coarticulation (realized by greater vowel nasalization, F1 bandwidth, and diphthongization on vowels in CVN contexts). Results showed no differences across listeners’ identification for Extensively coarticulated vowels, as well as oral vowels by both types of speakers (all at-ceiling). Yet, performance for the Minimal Coarticulators’ nasalized vowels was lowest for the older listener group and increased over apparent-time. Perceptual cue-weighting analyses revealed that older listeners rely more on F1 bandwidth, while younger listeners rely more on acoustic nasality, as coarticulatory cues providing information about lexical identity. Thus, there is evidence for variation in apparent- time in the use of the different coarticulatory cues present on vowels. Younger listeners’ cue weighting allows them flexibility to identify lexical items given a range of coarticulatory variation across (here, younger) speakers, while older listeners’ cue weighting leads to reduced performance for talkers producing innovative phonetic forms. This study contributes to our understanding of the relationship between multidimensional acoustic features resulting from coarticulation and the perceptual re-weighting of cues that can lead to sound change over time. 

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5. Talker-specific perceptual adaptation to second-language speech-in-noise: Tuning-in to the talker while tuning-out the noise

   https://doi.org/10.1121/10.0036844  

   Kim, Seung-Eun; Goldrick, Matthew; Bradlow, Ann_R (June 2025, The Journal of the Acoustical Society of America)

   When listeners encounter a difficult-to-understand talker in a difficult-to-understand situation, their perceptual mechanisms can adapt, making the talker in the situation easier to understand. This study examined talker-specific perceptual adaptation experimentally by embedding speech from second-language (L2) English talkers in varying levels of noise and collecting transcriptions from first-language English listeners (ten talkers, 100 listeners per experiment). Experiments 1 and 2 demonstrated that prior experience with a L2 talker's speech presented first without noise and then with gradually increasing levels of noise facilitated recognition of that talker in loud noise. Experiment 3 tested whether adaptation is driven by tuning-in to the talker's voice and speech patterns, by examining recognition of speech-in-loud-noise following experience with the talker in quiet. Finally, experiment 4 tested whether adaptation is driven by tuning-out the background noise, by measuring speech-in-loud-noise recognition after experience with the talker in consistently loud noise. The results showed that both tuning-in to the talker and tuning-out the noise contribute to talker-specific perceptual adaptation to L2 speech-in-noise. 

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