Perception Of Accented Speech Research Articles

Auditory cortex encodes lipreading information through spatially distributed activity

Watching a speaker's face improves speech perception accuracy. This benefit is enabled, in part, by implicit lipreading abilities present in the general population. While it is established that lipreading can alter the perception of a heard word, it is unknown how these visual signals are represented in the auditory system or how they interact with auditory speech representations. One influential, but untested, hypothesis is that visual speech modulates the population-coded representations of phonetic and phonemic features in the auditory system. This model is largely supported by data showing that silent lipreading evokes activity in the auditory cortex, but these activations could alternatively reflect general effects of arousal or attention or the encoding of non-linguistic features such as visual timing information. This gap limits our understanding of how vision supports speech perception. To test the hypothesis that the auditory system encodes visual speech information, we acquired functional magnetic resonance imaging (fMRI) data from healthy adults and intracranial recordings from electrodes implanted in patients with epilepsy during auditory and visual speech perception tasks. Across both datasets, linear classifiers successfully decoded the identity of silently lipread words using the spatial pattern of auditory cortex responses. Examining the time course of classification using intracranial recordings, lipread words were classified at earlier time points relative to heard words, suggesting a predictive mechanism for facilitating speech. These results support a model in which the auditory system combines the joint neural distributions evoked by heard and lipread words to generate a more precise estimate of what was said.

Evidence for a Causal Dissociation of the McGurk Effect and Congruent Audiovisual Speech Perception via TMS to the Left pSTS.

Congruent visual speech improves speech perception accuracy, particularly in noisy environments. Conversely, mismatched visual speech can alter what is heard, leading to an illusory percept that differs from the auditory and visual components, known as the McGurk effect. While prior transcranial magnetic stimulation (TMS) and neuroimaging studies have identified the left posterior superior temporal sulcus (pSTS) as a causal region involved in the generation of the McGurk effect, it remains unclear whether this region is critical only for this illusion or also for the more general benefits of congruent visual speech (e.g., increased accuracy and faster reaction times). Indeed, recent correlative research suggests that the benefits of congruent visual speech and the McGurk effect rely on largely independent mechanisms. To better understand how these different features of audiovisual integration are causally generated by the left pSTS, we used single-pulse TMS to temporarily disrupt processing within this region while subjects were presented with either congruent or incongruent (McGurk) audiovisual combinations. Consistent with past research, we observed that TMS to the left pSTS reduced the strength of the McGurk effect. Importantly, however, left pSTS stimulation had no effect on the positive benefits of congruent audiovisual speech (increased accuracy and faster reaction times), demonstrating a causal dissociation between the two processes. Our results are consistent with models proposing that the pSTS is but one of multiple critical areas supporting audiovisual speech interactions. Moreover, these data add to a growing body of evidence suggesting that the McGurk effect is an imperfect surrogate measure for more general and ecologically valid audiovisual speech behaviors.

The Accent Atlas: Effects of long-term exposure to nonnative accents on adaptive speech perception

As mobility increases and virtual interactions grow, quickly adapting to diverse accents is essential for effective communication. While lab-based accent training promotes rapid adaptation to unfamiliar accents, whether prolonged environmental exposure to linguistic diversity yields similar benefits is unknown. We conducted a large-scale perceptual experiment involving 600 + participants across 15 U.S. states, utilizing a cross-modal word matching task to measure speech recognition in both non-native accented English and native English with background noise. Participants were recruited from linguistically diverse (LD) or linguistically homogeneous (LH) states. Linguistic diversity was defined based on the prevalence of non-English speaking residents (U.S. census data). Our findings were twofold: firstly, consistent with prior studies, only exposure to non-native accented speech—but not exposure to speech in noise—improved recognition of novel talkers with the same accent; secondly, individuals from the LD states outperformed those from LH areas in initial accented speech perception. However, by the end of the experiment, benefits from in-lab accent exposure did not differ significantly between the two groups, suggesting that short-term training could mitigate long-term environmental influences. These results illuminate the interplay between daily linguistic environments and accent adaptation, enhancing our understanding of speech perception's adaptivity in a multilingual context.

Discrimination of Second Language Vowel Contrasts and the Role of Phonological Short-Term Memory and Nonverbal Intelligence

Although extensive research has focused on the perceptual abilities of second language (L2) learners, a significant gap persists in understanding how cognitive functions like phonological short-term memory (PSTM) and nonverbal intelligence (IQ) impact L2 speech perception. This study sets out to investigate the discrimination of L2 English monophthongal vowel contrasts and to assess the effect of PSTM and nonverbal IQ on L2 speech perception. The participants consisted of adult monolingually-raised Greek speakers, who completed an AX discrimination test, a digit span test, and a nonverbal intelligence test. A control group of English speakers also completed the AX test. Data were analyzed using Bayesian regression models. The results revealed that Greek speakers exhibited below chance discrimination for the majority of L2 vowel contrasts, consistently underperforming in comparison to the control group. Intriguingly, the study did not provide substantial evidence in favor of more accurate discrimination of L2 contrasts by Greek participants with high PSTM compared to those with low PSTM. However, the study yielded compelling evidence indicating that Greek participants with higher IQ demonstrated superior accuracy in discriminating most L2 contrasts compared to their lower IQ counterparts. The limited influence of PSTM on speech perception suggests the need for further exploration, considering the potential impact of test methodologies and the intricate interplay of other confounding factors. Furthermore, the study uncovers a noteworthy relationship between nonverbal IQ and L2 speech perception, likely linked with the association of high IQ with enhanced attentional capacities, information processing abilities, and learning skills—all of which are pivotal for accurate speech perception.

Preliminary Speech Perception Performance Profiles of School-Age Children With Childhood Apraxia of Speech, Speech Sound Disorder, and Typical Development.

Limited research exists assessing speech perception in school-age children with speech sound disorder (SSD) and childhood apraxia of speech (CAS); despite early evidence that speech perception may lead to error-prone motor planning/programming. In this study, we examine speech perception performance in school-age children with and without speech production deficits. Speech perception was assessed using the Wide Range Acoustic Accuracy Scale to determine the just-noticeable difference in discrimination for three consonant-vowel syllable contrasts (/bɑ/-/wɑ/, /dɑ/-/gɑ/, /ɹɑ/-/wɑ/), each varying along a single acoustic parameter for seven children with CAS with rhotic errors, seven children with SSD with rhotic errors, and seven typically developing (TD) children. Findings revealed statistically significant mean differences between perceptual performance of children with CAS when compared to TD children for discrimination of /ɹɑ/-/wɑ/ contrasts. Large effect sizes were also observed for comparisons of /ɹɑ/-/wɑ/ contrasts between children with CAS, SSD, and TD peers. Additionally, large effect sizes were observed for /dɑ/-/gɑ/ contrasts between children with CAS and SSD and TD children despite nonsignificant mean differences in group performance. Overall, mean outcome scores suggest that school-age children with CAS and persistent rhotic errors demonstrated less accurate speech perception skills relative to TD children for the /ɹɑ/-/wɑ/ contrasts. However, the relatively small sample sizes per group limit the extent to which these findings may be generalized to the broader population.

Speech intelligibility and listening effort: A dual-task paradigm for accented speech perception

Unfamiliar accents can make speech communication difficult, both by reducing speech intelligibility and by increasing the effort listeners must put forth to understand speech. In general, intelligibility refers to the proportion of words that a listener can correctly identify (100%, 50%, etc.), while listening effort refers to the cognitive resources that must be devoted to a difficult listening task. Generally, lower intelligibility is related to higher effort. However, it is now apparent that these two constructs, while related, are independent: for example, two 100% intelligible speakers may elicit different amounts of effort. To better characterize the relationship between intelligibility and effort, this study presents speakers of four intelligibility levels (one L1 English speaker, and three Mandarin-accented English speakers) within a dual-task paradigm (featuring a vibrotactile secondary task) to measure listening effort. We hypothesize an inverse relationship between intelligibility and effort, but the shape and slope of this relationship are of primary interest. These results will begin to illuminate the relationship between intelligibility and effort across a more continuous range of accent intelligibility. Data collection is ongoing. Results for the Mandarin Chinese accent will be presented. Preliminary results for the study’s second iteration (using a Korean accent) will also be presented.

Exploring the Implications of Input Variability for Unfamiliar Accented Speech Perception: A Focused Review and New Hypotheses

Children with and without communication disorders have difficulty understanding words and sentences produced by talkers with unfamiliar characteristics, such as unfamiliar accents. To date, few studies have investigated how this difficulty manifests in linguistically diverse children. Studies of monolingual children have found that lexical and phonological skills predict accurate perception. For linguistically diverse children, there are differences in the structure of their linguistic input relative to their monolingual peers. These differences in their linguistic input influence their lexical and phonological development, suggesting that they may also differ in how they perceive unfamiliar accented speech. In this paper we present different hypotheses for how input variability might affect unfamiliar accented speech perception. Then, we conduct a focused review of the literature on how input variability affects early linguistic development for bilingual and bidialectal children. We link this information to the literature on how children with and without language disorders understand unfamiliar accented speech to identify important areas for future inquiry. Determining how input variability interacts with linguistic skills to predict unfamiliar speech perception is a crucial area for future inquiry. Effective clinical recommendations and educational accommodations require understanding of the linguistic skills and experience that support accurate variable speech perception for diverse populations.

Quantifying the Influence of Factors on the Accuracy of Speech Perception in Mandarin-Speaking Cochlear Implant Patients.

Rehabilitation of hearing perception in cochlear implant (CI) patients is a challenging process. A comprehensive analysis of the characteristics of hearing rehabilitation in Mandarin-speaking CI patients was conducted. We measured the aided hearing threshold (AHT) and the speech perception accuracy (SPA) and collected clinical data. A total of 49 CI patients were included. Significant linear relationships existed between the AHT and SPA. The SPA increased by about 5-7% when the AHT decreased by 5 dB. An apparent individual difference in the SPA was observed under the same AHT, which in some patients was lower than the reference value fitted by the regression model. The timing of both of cochlear implantation and rehabilitation training was found to lead to significant improvement in SPA. The SPA increases by 2.1-3.6% per year of cochlear implantation and 0.7-1.5% per year of rehabilitation training. The time of auditory deprivation can significantly reduce the SPA by about 1.0-1.6% per year. The SPA was still poor in some CI patients when the hearing compensation seemed satisfying. Early cochlear implantation and post-operative rehabilitation are essential for recovery of the patient's SPA if the indications for cochlear implantation are met.

Auditory Perceptual Exercises in Adults Adapting to the Use of Hearing Aids.

Older adults with age-related hearing loss often use hearing aids (HAs) to compensate. However, certain challenges in speech perception, especially in noise still exist, despite today’s HA technology. The current study presents an evaluation of a home-based auditory exercises program that can be used during the adaptation process for HA use. The home-based program was developed at a time when telemedicine became prominent in part due to the COVID-19 pandemic. The study included 53 older adults with age-related symmetrical sensorineural hearing loss. They were divided into three groups depending on their experience using HAs. Group 1: Experienced users (participants who used bilateral HAs for at least 2 years). Group 2: New users (participants who were fitted with bilateral HAs for the first time). Group 3: Non-users. These three groups underwent auditory exercises for 3 weeks. The auditory tasks included auditory detection, auditory discrimination, and auditory identification, as well as comprehension with basic (syllables) and more complex (sentences) stimuli, presented in quiet and in noisy listening conditions. All participants completed self-assessment questionnaires before and after the auditory exercises program and underwent a cognitive test at the end. Self-assessed improvements in hearing ability were observed across the HA users groups, with significant changes described by new users. Overall, speech perception in noise was poorer than in quiet. Speech perception accuracy was poorer in the non-users group compared to the users in all tasks. In sessions where stimuli were presented in quiet, similar performance was observed among new and experienced uses. New users performed significantly better than non-users in all speech in noise tasks; however, compared to the experienced users, performance differences depended on task difficulty. The findings indicate that HA users, even new users, had better perceptual performance than their peers who did not receive hearing aids.

Online Assessment of Speech Perception and Auditory Spectrotemporal Processing in Spanish-English Bilinguals.

There is limited access to audiology services for the growing population of Spanish-English bilinguals in the United States. Online auditory testing can potentially provide a cost-effective alternative to in-person visits. However, even for bilinguals with high English proficiency, age of English acquisition may affect speech perception accuracy. This study used a comprehensive test battery to assess speech perception and spectrotemporal processing abilities in Spanish-English bilinguals and to evaluate susceptibility of different tests to effects of native language. The online battery comprised three tests of speech in quiet (vowel and consonant identification and words in sentences), four tests of speech perception in noise (two for intelligibility and two for comprehension), and three tests of spectrotemporal processing (two tests of stochastically modulated pattern discrimination and one test of spectral resolution). Participants were 28 adult Spanish-English bilinguals whose English acquisition began either early (≤ 6 years old) or late (≥ 7 years old) and 18 English monolingual speakers. Significant differences were found in six of the 10 tests. The differences were most pronounced for vowel perception in quiet, speech-in-noise test, and two tests of speech comprehension in noise. Late bilinguals consistently scored lower than native English speakers or early bilinguals. In contrast, no differences between groups were observed for digits-in-noise or three tests of spectrotemporal processing abilities. The findings suggest initial feasibility of online assessment in this population and can inform selection of tests for auditory assessment of Spanish-English bilinguals.

Listener engagement: the missing link in research on accented speech

Abstract Reverse linguistic stereotyping (RLS) is a process whereby a speaker’s perceived group membership triggers differential perception of aspects of their speech. RLS has been suggested to cause drops in intelligibility and recall, though why perception of a non-existent accent can negatively affect listening outcomes has not been sufficiently elucidated. The current study suggests an explanation may lie in differential levels of engagement among listeners. A sample of 430 Japanese university students listened to a short speech from either a speaker of Chinese Pronunciation of English or Received Pronunciation and rated them on aesthetics, comprehensibility, perceived intelligibility, engagement, and recall. Multiple linear regression suggested that only engagement served as a significant predictor to recall, though the other variables all had significant indirect effects when engagement was included as a mediating variable. These results indicated that listener engagement is a key variable which may help improve our understanding of accented speech perception.

Visual speech differentially modulates beta, theta, and high gamma bands in auditory cortex.

Speech perception is a central component of social communication. Although principally an auditory process, accurate speech perception in everyday settings is supported by meaningful information extracted from visual cues. Visual speech modulates activity in cortical areas subserving auditory speech perception including the superior temporal gyrus (STG). However, it is unknown whether visual modulation of auditory processing is a unitary phenomenon or, rather, consists of multiple functionally distinct processes. To explore this question, we examined neural responses to audiovisual speech measured from intracranially implanted electrodes in 21 patients with epilepsy. We found that visual speech modulated auditory processes in the STG in multiple ways, eliciting temporally and spatially distinct patterns of activity that differed across frequency bands. In the theta band, visual speech suppressed the auditory response from before auditory speech onset to after auditory speech onset (-93 to 500 ms) most strongly in the posterior STG. In the beta band, suppression was seen in the anterior STG from -311 to -195 ms before auditory speech onset and in the middle STG from -195 to 235 ms after speech onset. In high gamma, visual speech enhanced the auditory response from -45 to 24 ms only in the posterior STG. We interpret the visual-induced changes prior to speech onset as reflecting crossmodal prediction of speech signals. In contrast, modulations after sound onset may reflect a decrease in sustained feedforward auditory activity. These results are consistent with models that posit multiple distinct mechanisms supporting audiovisual speech perception.

Manipulating listener attitudes toward accented talkers influences speech perception

We previously demonstrated that listeners' attitudes toward talkers with foreign accents is related to listeners' ability to perceive foreign-accented speech. In this study, we sought to determine if listeners' attitudes toward talkers with foreign accents are malleable and, if so, whether changing listeners' attitudes toward talkers with foreign accents would change the strength of the relationship between listeners' attitudes and listeners' speech perception accuracy. Specifically, we hypothesized that supporting listeners’ biases regarding non-native speech would lead to better speech perception performance. To test this hypothesis, we created short vignettes that either conformed to or violated listeners’ biases regarding non-native talkers. Native English-speaking listeners rated and transcribed speech produced by native and non-native English speakers. Half of the listeners read the vignette prior to rating the speech, half received no information about the talkers; vignettes were randomly paired with talkers. Contrary to our hypothesis, there was no effect of vignette type. Listeners rated non-native listeners as more accented and less likeable when vignettes were present. Interestingly, listeners were also more accurate transcribing speech by both native and non-native talkers when the vignettes were present.

Sustained neural rhythms reveal endogenous oscillations supporting speech perception.

Rhythmic sensory or electrical stimulation will produce rhythmic brain responses. These rhythmic responses are often interpreted as endogenous neural oscillations aligned (or "entrained") to the stimulus rhythm. However, stimulus-aligned brain responses can also be explained as a sequence of evoked responses, which only appear regular due to the rhythmicity of the stimulus, without necessarily involving underlying neural oscillations. To distinguish evoked responses from true oscillatory activity, we tested whether rhythmic stimulation produces oscillatory responses which continue after the end of the stimulus. Such sustained effects provide evidence for true involvement of neural oscillations. In Experiment 1, we found that rhythmic intelligible, but not unintelligible speech produces oscillatory responses in magnetoencephalography (MEG) which outlast the stimulus at parietal sensors. In Experiment 2, we found that transcranial alternating current stimulation (tACS) leads to rhythmic fluctuations in speech perception outcomes after the end of electrical stimulation. We further report that the phase relation between electroencephalography (EEG) responses and rhythmic intelligible speech can predict the tACS phase that leads to most accurate speech perception. Together, we provide fundamental results for several lines of research-including neural entrainment and tACS-and reveal endogenous neural oscillations as a key underlying principle for speech perception.

Revisiting Perception–Production Relationships: Exploring a New Approach to Investigate Perception as a Time‐Varying Predictor

AbstractModels of L2 pronunciation learning have hypothesized that accurate speech perception promotes accurate speech production. This claim can be evaluated longitudinally by examining the extent to which changes in stop consonant perception predict changes in stop consonant production. Taking a time‐sensitive view of the perception–production link, this study used longitudinal data to analyze perception as a time‐varying predictor of production accuracy. Mixed‐effects models were fit to oddity, delayed word repetition, and picture description tasks to examine how participants’ perception and production changed over time. Oddity task perception data were then decomposed into their between‐ and within‐subjects components and integrated into the delayed repetition and picture description production models. Surprisingly, only the between‐subjects predictors reached significance, and the strength of the perception–production link varied across production tasks and target phones. The methods used have implications for future research on perception–production links.

Effects of Gap Position on Perceptual Gap Detection Across Late Childhood and Adolescence.

The ability to detect a silent gap within a sound is critical for accurate speech perception, and gap detection has been shown to have an extended developmental trajectory. In certain conditions, the detectability of the gap decreases as the gap is placed closer to the beginning of the signal. Early in development, the detection of gaps shortly after signal onset may be especially difficult due to immaturities in the encoding and perception of rapidly changing sounds. The present study explored the development of gap detection from age 8 to 19years, specifically when the temporal placement of the gap varied. Performance improved with age for all temporal placements of the gap, demonstrating a gradual maturation of gap detection abilities throughout adolescence. Younger adolescents did not benefit from increasing gap onset times, while older adolescents' thresholds gradually improved as gap onset time lengthened. Regardless of age, listeners learned between the two testing days but did not improve within days. Younger adolescents had poorer thresholds for the last block of testing on the second day, returning to baseline performance despite learning between days. These data support earlier studies showing that gaps are harder to detect near stimulus onset and confirm that gap detection abilities continue to mature into adolescence. The data also suggest that younger adolescents do not receive the same benefit of increasing gap onset time and respond differently to repeated testing than older adolescents and young adults.

Anticipatory Baseline Pupil Diameter Is Sensitive to Differences in Hearing Thresholds.

Task-evoked changes in pupil dilation have long been used as a physiological index of cognitive effort. Unlike this response, that is measured during or after an experimental trial, the baseline pupil dilation (BPD) is a measure taken prior to an experimental trial. As such, it is considered to reflect an individual’s arousal level in anticipation of an experimental trial. We report data for 68 participants, ages 18 to 89, whose hearing acuity ranged from normal hearing to a moderate hearing loss, tested over a series 160 trials on an auditory sentence comprehension task. Results showed that BPDs progressively declined over the course of the experimental trials, with participants with poorer pure tone detection thresholds showing a steeper rate of decline than those with better thresholds. Data showed this slope difference to be due to participants with poorer hearing having larger BPDs than those with better hearing at the start of the experiment, but with their BPDs approaching that of the better hearing participants by the end of the 160 trials. A finding of increasing response accuracy over trials was seen as inconsistent with a fatigue or reduced task engagement account of the diminishing BPDs. Rather, the present results imply BPD as reflecting a heightened arousal level in poorer-hearing participants in anticipation of a task that demands accurate speech perception, a concern that dissipates over trials with task success. These data taken with others suggest that the baseline pupillary response may not reflect a single construct.

Impact of cognitive load and sentence predictability on cognitive spare capacity in elderly adults with hearing loss

Listening effort is needed to understand speech that is degraded by hearing loss and/or a noisy environment, and this in turn reduces cognitive spare capacity (CSC), the amount of cognitive resources available for allocation to concurrent tasks. Sentence context is known to boost speech perception accuracy, but how does context affect CSC? Here, we examine the impacts of context and cognitive (memory) load on behavioral measures of CSC. Elderly, hearing-impaired adults listened to noise-masked, spoken sentences in which sentence-final words were either predictable or unpredictable. Each trial began with visual presentation of a short (low load) or long (high load) sequence of to-be-remembered digits. Accuracy and response times for word recognition and digit recall were both facilitated by sentence predictability, indicating that CSC was greater when sentences were predictable. In addition, response times for both words and digits and accuracy for digits were impaired in the high load condition, reflecting decreased CSC under cognitive load. Participants’ baseline cognitive capacity (from a pre-test of working memory) generally did not moderate these effects. Results support the idea that predictable sentence contexts can support CSC and thereby improve ease of listening in elderly adults with hearing loss.

Auditory temporal processing, reading, and phonological awareness among aging adults

Auditory temporal processing (ATP) has been related in the literature to both speech perception as well as reading and phonological awareness. In aging adults, it is known to be related to difficulties in speech perception. In the present study, we aimed to test whether an age-related deficit in ATP would also be accompanied by poor reading and phonological awareness. Thirty-eight aging adults were compared to 55 readers with dyslexia and 42 young normal readers on temporal order judgment (TOJ), speech perception, reading, and phonological awareness tests. Aging adults had longer TOJ thresholds than young normal readers, but shorter than readers with dyslexia; however, they had lower speech perception accuracy than both groups. Phonological awareness of the aging adults was better than readers with dyslexia, but poorer than young normal readers, although their reading accuracy was similar to that of the young controls. This is the first report on poor phonological awareness among aging adults. Suprisingly, it was not accompanied by difficulties in reading ability, and might instead be related to aging adults' difficulties in speech perception. This newly discovered relationship between ATP and phonological awareness among aging adults appears to extend the existing understanding of this relationship, and suggests it should be explored in other groups with ATP deficits.

2333 Impact of spoken sentence predictability on cognitive spare capacity in elderly adults with hearing loss

OBJECTIVES/SPECIFIC AIMS: Listening effort is needed to understand speech that is degraded by hearing loss and/or a noisy environment. Effortful listening reduces cognitive spare capacity (CSC). Predictive contexts aid speech perception accuracy, but it is not known whether the use of context reduces or preserves CSC. Here, we compare the impact of predictive context and cognitive load on behavioral indices of CSC in elderly, hearing-impaired adults. METHODS/STUDY POPULATION: Elderly, hearing-impaired adults listened in a noisy background to spoken sentences in which sentence-final words were either predictable or not predictable based on the sentence context. Cognitive load was manipulated by asking participants to remember either short or long sequences of visually presented digits. Participants were divided into low or high cognitive capacity groups based on a pretest of working memory. Accuracy and response times were examined for report of both sentence-final words and digit sequences. RESULTS/ANTICIPATED RESULTS: Preliminary results indicate that accuracy and response times for both words and digits were facilitated by sentence predictability, suggesting that the use of predictive sentence context preserves CSC. Response times for both words and digits and accuracy for digits were impaired under cognitive load. Trends were similar across high and low cognitive capacity groups. The preliminary results support the idea that habilitation strategies involving context use could potentially support CSC in elderly, hearing-impaired adults. DISCUSSION/SIGNIFICANCE OF IMPACT: These preliminary results support the concept that habilitation strategies involving context use could potentially support CSC in elderly, hearing-impaired adults.