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1. Atypical context-dependent speech processing in autism

   https://doi.org/10.1017/S0142716420000387  

   Yu, Alan Chi; To, Carol Kit (September 2020, Applied Psycholinguistics)

   null (Ed.)

   Abstract The ability to take contextual information into account is essential for successful speech processing. This study examines individuals with high-functioning autism and those without in terms of how they adjust their perceptual expectation while discriminating speech sounds in different phonological contexts. Listeners were asked to discriminate pairs of sibilant-vowel monosyllables. Typically, discriminability of sibilants increases when the sibilants are embedded in perceptually enhancing contexts (if the appropriate context-specific perceptual adjustment were performed) and decreases in perceptually diminishing contexts. This study found a reduction in the differences in perceptual response across enhancing and diminishing contexts among high-functioning autistic individuals relative to the neurotypical controls. The reduction in perceptual expectation adjustment is consistent with an increase in autonomy in low-level perceptual processing in autism and a reduction in the influence of top-down information from surrounding information. 

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2. Naturalistic speech supports distributional learning across contexts

   https://doi.org/10.1073/pnas.2123230119  

   Hitczenko, Kasia; Feldman, Naomi H. (September 2022, Proceedings of the National Academy of Sciences)

   At birth, infants discriminate most of the sounds of the world’s languages, but by age 1, infants become language-specific listeners. This has generally been taken as evidence that infants have learned which acoustic dimensions are contrastive, or useful for distinguishing among the sounds of their language(s), and have begun focusing primarily on those dimensions when perceiving speech. However, speech is highly variable, with different sounds overlapping substantially in their acoustics, and after decades of research, we still do not know what aspects of the speech signal allow infants to differentiate contrastive from noncontrastive dimensions. Here we show that infants could learn which acoustic dimensions of their language are contrastive, despite the high acoustic variability. Our account is based on the cross-linguistic fact that even sounds that overlap in their acoustics differ in the contexts they occur in. We predict that this should leave a signal that infants can pick up on and show that acoustic distributions indeed vary more by context along contrastive dimensions compared with noncontrastive dimensions. By establishing this difference, we provide a potential answer to how infants learn about sound contrasts, a question whose answer in natural learning environments has remained elusive. 

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3. Modeling adaptation to a novel accent

   Hitczenko, Kasia; Feldman, Naomi H. (August 2016, Proceedings of the Annual Conference of the Cognitive Science Society)

   Listeners quickly adapt to novel accents. There are three main hypotheses for how they do so. Some suggest that listeners expand their phonetic categories, allowing more variability in how a sound is pronounced. Others argue that listeners shift their categories instead, only accepting deviations consistent with the accent. A third hypothesis is that listeners both shift and expand their categories. Most work has supported the category expansion hypotheses, with the key exception of Maye et al. (2008) who argued for a shifting strategy. Here, we apply the ideal adaptor model from Kleinschmidt & Jaeger (2015) to reexamine what conclusions can be drawn from their data. We compare adaptation models in which categories are shifted, expanded, or both shifted and expanded. We show that models involving expansion can explain the data as well as, if not better than, the shift model, in contrast to what has been previously concluded from these data. 

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4. What defines a category? Evidence that listeners’ perception is governed by generalizations

   Richardson, Rachael R.; Feldman, Naomi H.; Idsardi, William (August 2015, Proceedings of the Annual Conference of the Cognitive Science Society)

   Listeners draw on their knowledge of phonetic categories when identifying speech sounds, extracting meaningful structural features from auditory cues. We use a Bayesian model to investigate the extent to which their perceptions of linguistic content incorporate their full knowledge of the phonetic category structure, or only certain aspects of this knowledge. Simulations show that listeners are best modeled as attending primarily to the most salient phonetic feature of a category when interpreting a cue, possibly attending to other features only in cases of high ambiguity. These results support the conclusion that listeners ignore potentially informative correlations in favor of efficient communication. 

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5. 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 (October 2023, 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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