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1. Speech perception in younger and older adults: Cue-weighting and contextual information

   Cheng, R (September 2023, Proquest)

   This dissertation compared speech perception across younger and older normal-hearing adults. We ask four research questions to assess acoustic cue weighting and the role of contextual information (lexical information and speaking rate) in speech perception. Experiment 1 tested for age-related changes in cue-weighting. The absolute weights showed that older listeners relied on both VOT and F0 more than younger listeners, and some listeners’ reliance on VOT correlated with inhibitory control when perceiving the /d/-/t/ contrast. The relative weights suggested that older listeners relied on VOT less and F0 more than younger listeners. Experiment 2 tested whether younger and older listeners used different cue-weighting adjustment strategies in distributional learning. Both older and younger listeners adjusted their reliance on acoustic cues when the primary acoustic cue (VOT) became ambiguous. Older listeners adjusted F0 to a greater degree than younger listeners, while younger listeners adjusted VOT more than older listeners. With a lexically-guided learning paradigm, Experiment 3 explored if younger and older adults differed in their use of lexical information when learning to map acoustic tokens that were ambiguous. Older and younger listeners utilized the lexical context to the same extent. In Experiment 4, the contextual effect of speaking rate was examined by embedding voicing contrasts in short and long syllables and presenting these syllables to younger and older listeners. Older and younger listeners compensated for variation in speaking rate in a similar manner as younger listeners. The findings in perceptual learning demonstrate perceptual flexibility among normal-hearing older listeners, despite an assumed decline in temporal processing. 

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2. Rapid speech adaptation in younger and older normal-hearing adults: Distributional and lexically guided learning

   https://doi.org/10.1121/10.0011276  

   Cheng, Ruoqian; Jongman, Allard (April 2022, The Journal of the Acoustical Society of America)

   In speech perception, when a primary acoustic cue (e.g., VOT) is ambiguous, listeners may increase the weight of a secondary cue (e.g., F0). In experiment 1, we compared the cue-weighting adjustment strategies across younger and older normal-hearing adults with a distributional learning paradigm. Two groups of native English listeners were exposed to voicing contrasts that were ambiguous in either VOT or F0. Additionally, listeners may access lexical information to help resolve the ambiguity in the acoustic signal. Older listeners have been reported to use lexical information to a greater degree than younger listeners. In experiment 2, using a lexically guided learning paradigm, we tested if younger and older adults differ in their use of lexical information when learning to interpret ambiguous acoustic tokens. There were four types of exposure, in which stimuli differed in lexical status (day-*tay; *doy-toy) and the acoustic ambiguity involved either only VOT or both VOT and F0. Preliminary results from younger normal-hearing, listeners showed significant speech adaptation effects, with a significant change in cue weights in distributional learning and salient lexical bias in lexically guided learning. More data will be collected from older adults to assess the extent of perceptual learning relative to younger adults. 

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3. Transfer of statistical learning from passive speech perception to speech production

   https://doi.org/10.3758/s13423-023-02399-8  

   Murphy, Timothy K; Nozari, Nazbanou; Holt, Lori L (June 2024, Psychonomic Bulletin & Review)

   Abstract Communicating with a speaker with a different accent can affect one’s own speech. Despite the strength of evidence for perception-production transfer in speech, the nature of transfer has remained elusive, with variable results regarding the acoustic properties that transfer between speakers and the characteristics of the speakers who exhibit transfer. The current study investigates perception-production transfer through the lens of statistical learning across passive exposure to speech. Participants experienced a short sequence of acoustically variable minimal pair (beer/pier) utterances conveying either an accent or typical American English acoustics, categorized a perceptually ambiguous test stimulus, and then repeated the test stimulus aloud. In thecanonicalcondition, /b/–/p/ fundamental frequency (F0) and voice onset time (VOT) covaried according to typical English patterns. In thereversecondition, the F0xVOT relationship reversed to create an “accent” with speech input regularities atypical of American English. Replicating prior studies, F0 played less of a role in perceptual speech categorization in reverse compared with canonical statistical contexts. Critically, this down-weighting transferred to production, with systematic down-weighting of F0 in listeners’ own speech productions in reverse compared with canonical contexts that was robust across male and female participants. Thus, the mapping of acoustics to speech categories is rapidly adjusted by short-term statistical learning across passive listening and these adjustments transfer to influence listeners’ own speech productions. 

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4. Bears don’t always mess with beers: Limits on generalization of statistical learning in speech

   https://doi.org/10.3758/s13423-025-02690-w  

   Murphy, Timothy K; Nozari, Nazbanou; Holt, Lori L (April 2025, Psychonomic Bulletin & Review)

   Abstract Perception changes rapidly and implicitly as a function of passive exposure to speech that samples different acoustic distributions. Past research has shown that this statistical learning generalizes across talkers and, to some extent, new items, but these studies involved listeners’ active engagement in processing statistics-bearing stimuli. In this study, we manipulated the relationship between voice onset time (VOT) and fundamental frequency (F0) to establish distributional regularities either aligned with American English or reversed to create a subtle foreign accent. We then tested whether statistical learning across passive exposure to these distributions generalized to new items never experienced in the accent. Experiment 1 showed statistical learning across passive exposure but no generalization of learning when exposure and test items shared the same initial consonant but differed in vowels (bear/pear → beer/pier) or when they differed in initial consonant but shared distributional regularities across VOT and F0 dimensions (deer/tear → beer/pier). Experiment 2 showed generalization to stimuli that shared the statistics-bearing phoneme (bear/pear → beer/pier), but only when the response set included tokens from both exposure and generalization stimuli. Moreover, statistical learning transferred to influence the subtle acoustics of listeners’ own speech productions but did not generalize to influence productions of stimuli not heard in the accent. In sum, passive exposure is thus sufficient to support statistical learning and its generalization, but task demands modulate this dynamic. Moreover, production does not simply mirror perception: generalization in perception was not accompanied by transfer to production. 

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5. 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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