The effect of native vowel processing ability and frequency discrimination acuity on the phonetic training of English vowels for native speakers of Greek

Individual differences in the consistency of neural and behavioural responses to speech sounds

There are documented individual differences among adults in the consistency of speech sound processing, both at neural and behavioural levels. Some adults show more consistent neural responses to speech sounds than others, as measured by an event-related potential called the frequency-following response (FFR); similarly, some adults show more consistent behavioural responses to native speech sounds than others, as measured by two-alternative forced choice (2AFC) and visual analog scaling (VAS) tasks. Adults also differ in how successfully they can perceive non-native speech sounds. Interestingly, it remains unclear whether these differences are related within individuals. In the current study, native English-speaking adults completed native phonetic perception tasks (2AFC and VAS), a non-native (German) phonetic perception task, and an FFR recording session. From these tasks, we derived measures of the consistency of participants' neural and behavioural responses to native speech as well as their non-native perception ability. We then examined the relationships among individual differences in these measures. Analysis of the behavioural measures revealed that more consistent responses to native sounds predicted more successful perception of unfamiliar German sounds. Analysis of neural and behavioural data did not reveal clear relationships between FFR consistency and our phonetic perception measures. This multimodal work furthers our understanding of individual differences in speech processing among adults, and may eventually lead to individualized approaches for enhancing non-native language acquisition in adulthood.

Learning English vowels: The effects of different phonetic training modes on Arabic learners' production and perceptiona)

This study investigated the effect of different types of phonetic training on potential changes in the production and perception of English vowels by Arabic learners of English. Forty-six Arabic learners of English were randomly assigned to one of three high variability vowel training programs: Perception training (High Variability Phonetic Training), Production training, and a Hybrid Training program (production and perception training). Pre- and post-tests (vowel identification, category discrimination, speech recognition in noise, and vowel production) showed that all training types led to improvements in perception and production. There was some evidence that improvements were linked to training type: learners in the Perception Training condition improved in vowel identification but not vowel production, while those in the Production Training condition showed only small improvements in performance on perceptual tasks, but greater improvement in production. However, the effects of training modality were complicated by proficiency, with high proficiency learners benefitting more from different types of training regardless of training mode than lower proficiency learners.

The Effect of Computer-Based Auditory Training on Speech-in-Noise Perception in Adults: a Systematic Review and Meta-Analysis

To investigate the effectiveness of computer-based auditory training on speech-in-noise perception in adults. With no language restriction, 11 databases were searched from 1990 to 2020. We included any clinical trial studies with concurrent comparison groups that examined the effectiveness of computer-based auditory training programs in adults. The primary outcome was a speech in noise perception that was estimated using the "difference pretest-posttest-control" index (dppc2). The risk of bias was assessed using the Cochrane collaboration tool for assessing the risk of bias in randomized trials. The certainty of the evidence was investigated using the GRADE in two primary outcomes. Twenty three studies were included in two subgroups based on primary outcome: 12 studies with speech perception threshold and 11 studies with speech-in-noise test scores. Computer-based auditory training resulted in a speech in noise perception improvement (dppc2:  -0.69, 95%CI:  -1.11 to  -0.26; I2 = 69.6%, p = 0.00) and (dppc2: 0.71, 95%CI: 0.38-1.03, I2: 17.8%, p = 0.27) respectively in both subgroups. 19 studies were judged to have a high risk of bias and 3 studies had a low risk of bias and the strength of the evidence was low in both primary outcomes. This finding indicates that computer-based auditory training can be a moderately effective intervention for speech-in-noise perception in adults. However, due to the low quality of primary studies and the low certainty of the evidence, the results are not yet definite. Prospero registration number: CRD42021233193.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-023-03920-0.

Improving non-native duration contrast with dichotic training in dyslexic and non-dyslexic individuals

Perceiving and producing English phonemic vowel length contrasts is challenging for non-native speakers. According to multi-time resolution models, endogenous slow/fast rhythms contribute, respectively, in the right/left hemispheres, to long/short acoustic cue processing. This study introduced a perceptual training method implementing dichotic stimulation to improve /i:/-/ɪ/ processing by promoting hemispheric complementarity. Twenty non-dyslexic and 20 dyslexic French adults received 1 hr-training over 3 days. Productions were evaluated with pre-/post-tests. Training enhanced vowel duration contrast in word production by /i:/ lengthening and /ɪ/ shortening in both groups. Adults with dyslexia compensated fewer /i:/ lengthening by /ɪ/ shortening than did non-dyslexic adults. Transfer from perceptual training to production seems possible for foreign-language learning even in dyslexic adults. The extent to which dichotic presentation contributed to training effectiveness cannot be evaluated here, but the triggering of lengthening and shortening mechanisms suggests that lateralized complementary skills have been enhanced by dichotic stimulation.

Memory-card vowel training for child and adult second-language learners: A first report

Japanese adults and Spanish-Catalan children received auditory phonetic training for English vowels using a novel paradigm, a version of the common children's card game Concentration. Individuals played a computer-based game in which they turned over pairs of cards to match spoken words, drawn from sets of vowel minimal pairs. The training was effective for adults, improving vowel recognition in a game that did not explicitly require identification. Children likewise improved over time on the memory card game, but not on the present generalisation task. This gamified training method can serve as a platform for examining development and perceptual learning.

Training non-native vowel perception: In quiet or noise

Noise makes speech perception much more challenging for non-native listeners than for native listeners. Training for non-native speech perception is usually implemented in quiet. It remains unclear if background noise may benefit or hamper non-native speech perception learning. In this study, 51 Chinese-native listeners were randomly assigned into three groups, including vowel training in quiet (TIQ), vowel training in noise (TIN), and watching videos in English as an active control. Vowel identification was assessed before (T1), right after (T2), and three months after training (T3) in quiet and various noise conditions. Results indicated that compared with the video watching group, the TIN group improved vowel identification in both quiet and noise significantly more at T2 and at T3. In contrast, the TIQ group improved significantly more in quiet and also in non-speech noise conditions at T2, but the improvement did not hold at T3. Moreover, compared to the TIQ group, the TIN group showed significantly less informational masking at both T2 and T3 and less energetic masking at T3. These results suggest that L2 speech training in background noise may improve non-native vowel perception more effectively than TIQ background only. The implications for non-native speech perception learning are discussed.

The effects of high versus low talker variability and individual aptitude on phonetic training of Mandarin lexical tones

High variability (HV) training has been found to be more effective than low variability (LV) training when learning various non-native phonetic contrasts. However, little research has considered whether this applies to the learning of tone contrasts. The only two relevant studies suggested that the effect of HV training depends on the perceptual aptitude of participants (Perrachione et al., 2011; Sadakata & McQueen, 2014). The present study extends these findings by examining the interaction between individual aptitude and input variability using natural, meaningful second language input (both previous studies used pseudowords). A total of 60 English speakers took part in an eight session phonetic training paradigm. They were assigned to high/low/high-blocked variability training groups and learned real Mandarin tones and words. Individual aptitude was measured following previous work. Learning was measured using one discrimination task, one identification task and two production tasks. All tasks assessed generalization. All groups improved in both the production and perception of tones which transferred to untrained voices and items, demonstrating the effectiveness of training despite the increased complexity compared with previous research. Although the LV group exhibited an advantage with the training stimuli, there was no evidence for a benefit of high-variability in any of the tests of generalisation. Moreover, although aptitude significantly predicted performance in discrimination, identification and training tasks, no interaction between individual aptitude and variability was revealed. Additional Bayes Factor analyses indicated substantial evidence for the null for the hypotheses of a benefit of high-variability in generalisation, however the evidence regarding the interaction was ambiguous. We discuss these results in light of previous findings.

Successful second language learning is tied to robust domain-general auditory processing and stable neural representation of sound

There is a great deal of individual variability in outcome in second language learning, the sources of which are still poorly understood. We hypothesized that individual differences in auditory processing may account for some variability in second language learning. We tested this hypothesis by examining psychoacoustic thresholds, auditory-motor temporal integration, and auditory neural encoding in adult native Polish speakers living in the UK. We found that precise English vowel perception and accurate English grammatical judgment were linked to lower psychoacoustic thresholds, better auditory-motor integration, and more consistent frequency-following responses to sound. Psychoacoustic thresholds and neural sound encoding explained independent variance in vowel perception, suggesting that they are dissociable indexes of sound processing. These results suggest that individual differences in second language acquisition success stem at least in part from domain-general difficulties with auditory perception, and that auditory training could help facilitate language learning in some individuals with specific auditory impairments.

A Systematic Review of Interventions to Address Accent-Related Communication Problems in Healthcare

Background: Linguistic diversity in terms of speech, accent, and dialect can present a barrier to communication in healthcare. This review synthesizes current evidence on the effectiveness of interventions that target accent- or dialect-related communication problems in healthcare. Methods: Eligible studies were identified through a search of literature databases in 2018 using medical subject heading (MeSH) terms and additional keywords. Articles were screened for eligibility according to predetermined inclusion criteria. Because of the heterogeneity of the studies, effect data were analyzed using narrative synthesis. Results: Twenty-six studies (n=964) were included, reporting a range of interventions that provided accent modification training, role play or simulated patient consultation training, general language and consultation skills training, web-based training, and cultural competence training. Most studies (24 of the 26) indicated some benefits of the accent elements in the interventions based on objective or subjective measures. The key benefits were improvements in speech production, communication competence, and academic/clinical performance, as well as perceptual changes. Conclusion: Notwithstanding the low research quality and lack of standardized measures in the included studies, this review establishes an evidence base for implementing accent-related communication improvement strategies in healthcare. Large randomized controlled studies would be helpful to strengthen this evidence base.

High variability phonetic training in adaptive adverse conditions is rapid, effective, and sustained

This paper evaluates a novel high variability phonetic training paradigm that involves presenting spoken words in adverse conditions. The effectiveness, generalizability, and longevity of this high variability phonetic training in adverse conditions was evaluated using English phoneme contrasts in three experiments with Malaysian multilinguals. Adverse conditions were created by presenting spoken words against background multi-talker babble. In Experiment 1, the adverse condition level was set at a fixed level throughout the training and in Experiment 2 the adverse condition level was determined for each participant before training using an adaptive staircase procedure. To explore the effectiveness and sustainability of the training, phonemic discrimination ability was assessed before and immediately after training (Experiments 1 and 2) and 6 months after training (Experiment 3). Generalization of training was evaluated within and across phonemic contrasts using trained and untrained stimuli. Results revealed significant perceptual improvements after just three 20-minute training sessions and these improvements were maintained after 6 months. The training benefits also generalized from trained to untrained stimuli. Crucially, perceptual improvements were significantly larger when the adverse conditions were adapted before each training session than when it was set at a fixed level. As the training improvements observed here are markedly larger than those reported in the literature, this indicates that the individualized phonetic training regime in adaptive adverse conditions (HVPT-AAC) is highly effective at improving speech perception.

Computer-based auditory training improves second-language vowel production in spontaneous speech

The current study examined the effectiveness of computer-based auditory training on Greek speakers' production of English vowels in read sentences and in spontaneous speech. Another group of Greek speakers served as controls. Improvement was evaluated pre- and post-training via an identification task performed by English listeners and by an acoustic analysis of vowel quality using a combined F1/F2 measure. Auditory training improved English vowel production in read sentences and in spontaneous speech for the trained group, with improvement being larger in read sentences. The results indicate that auditory training can have ecological validity since it enhances learners' production beyond the (read) sentence level.

Perceptual Training of Second-Language Vowels: Does Musical Ability Play a Role?

The present study attempts to extend the research on the effects of phonetic training on the production and perception of second-language (L2) vowels. We also examined whether success in learning L2 vowels through high-variability intensive phonetic training is related to the learners' general musical abilities. Forty Azerbaijani learners of Standard Southern British English participated in a pre-test/training/post-test setting. Discrimination and production tests were used in pre- and post-tests. The participants' musical ability was evaluated through three musical aptitude tests. Results revealed a significant improvement in the discrimination and production of L2 vowels after training. However, the lack of a one-to-one relationship between production and perception gains suggests distinct representations underlying L2 speech perception and production. There was no significant correlation between overall musical ability scores and L2 vowel learning, however, results revealed a correlation between discrimination improvements and tonal memory. This suggests tonal memory facilitates the perceptual learning of the novel phonological structure of L2.

Successful non-native speech perception is linked to frequency following response phase consistency

Some people who attempt to learn a second language in adulthood meet with greater success than others. The causes driving these individual differences in second language learning skill continue to be debated. In particular, it remains controversial whether robust auditory perception can provide an advantage for non-native speech perception. Here, we tested English speech perception in native Japanese speakers through the use of frequency following responses, the evoked gamma band response, and behavioral measurements. Participants whose neural responses featured less timing jitter from trial to trial performed better on perception of English consonants than participants with more variable neural timing. Moreover, this neural metric predicted consonant perception to a greater extent than did age of arrival and length of residence in the UK, and neural jitter predicted independent variance in consonant perception after these demographic variables were accounted for. Thus, difficulties with auditory perception may be one source of problems learning second languages in adulthood.

Relationship between individual differences in speech processing and cognitive functions

A growing body of research has suggested that cognitive abilities may play a role in individual differences in speech processing. The present study took advantage of a widespread linguistic phenomenon of sound change to systematically assess the relationships between speech processing and various components of attention and working memory in the auditory and visual modalities among typically developed Cantonese-speaking individuals. The individual variations in speech processing are captured in an ongoing sound change-tone merging in Hong Kong Cantonese, in which typically developed native speakers are reported to lose the distinctions between some tonal contrasts in perception and/or production. Three groups of participants were recruited, with a first group of good perception and production, a second group of good perception but poor production, and a third group of good production but poor perception. Our findings revealed that modality-independent abilities of attentional switching/control and working memory might contribute to individual differences in patterns of speech perception and production as well as discrimination latencies among typically developed speakers. The findings not only have the potential to generalize to speech processing in other languages, but also broaden our understanding of the omnipresent phenomenon of language change in all languages.

The Effects of Language Dominance in the Perception and Production of the Galician Mid Vowel Contrasts

AIMS

This study investigates the perception and production of the Galician mid vowel contrasts by 54 early Spanish-Galician bilinguals in the cities of Vigo and Santiago (Galicia, Spain). Empirical data is provided to examine the role of language dominance in the perception and production of Galician mid vowel contrasts in order to determine whether the Galician vowel system is becoming more Spanish-like as a result of extensive contact with Spanish in urban areas.

METHODS

Perception and production data for each mid vowel contrast were collected in (1) binary forced-choice identification tasks, (2) AX discrimination tasks and (3) a reading-aloud task.

RESULTS

Results from binary forced-choice identification and AX discrimination tasks indicate that Spanish-dominant bilinguals have great difficulty in discriminating between these mid vowels while Galician-dominant subjects display a robust categorical identification of the two mid vowel categories. Acoustic analyses of their productions show that Galician-dominant bilinguals implement a Galician-specific /e/-/x025B;/ contrast but Spanish-dominant ones produce a single, merged Spanish-like front mid vowel. However, both language dominance groups seem to maintain a more robust /o/-/x0254;/ contrast. This asymmetry between front and back mid vowels is found in the productions of both language dominance groups.

CONCLUSION

These results show that language dominance is a strong predictor of the production and perception abilities of Spanish-Galician bilinguals, and that only Galician-dominant subjects in these urban areas possess two independent phonetic categories in the front and back mid vowel space.

More is less: pitch discrimination and language delays in children with optimal outcomes from autism

The autism spectrum disorders (ASD) are neurodevelopmental disorders diagnosed behaviorally but associated with differences in brain development. Individuals with ASD exhibit superior auditory perceptual skills, which may correlate with ASD symptomatology, particularly language skills. We describe findings from individuals diagnosed with ASD before age five, who now have no symptoms (e.g., having optimal outcomes). Unlike an ASD group, which shows heightened pitch discrimination, the Optimal Outcome group's abilities do not differ from those of typically developing controls. Furthermore, pitch discrimination is associated with both current autism symptomatology and early-language milestones. Findings illuminate processes associated with resolution of autism. We also discuss a specific mechanism by which heightened auditory discrimination leads to language delays in ASD.

Predicting Native English-Like Performance by Native Japanese Speakers

This study tested the predictions of the Speech Learning Model (SLM, Flege, 1988) on the case of native Japanese (NJ) speakers' perception and production of English /ɹ / and /l/. NJ speakers' degree of foreign accent, intelligibility of /ɹ -l/ productions, and ability to perceive natural speech /ɹ -l/ were assessed as a function of length of residency in North America, age of arrival in North America, years of student status in an English environment, and percentage of Japanese usage. Additionally, the extent to which NJ speakers' utilized the F3 onset cue when differentiating /ɹ -l/ in perception and production was assessed, this cue having previously been shown to be the most reliable indicator of category membership. As predicted, longer residencies predicted more native English-like accents, more intelligible productions, and more accurate natural speech identifications; however, no changes were observed in F3 reliance, indicating that though performance improves it does so through reliance on other cues.