Impact of speech rate on perception of vowel and consonant duration by bilinguals and monolinguals.

The perceptual boundary between short and long categories depends on speech rate. We investigated the influence of speech rate on perceptual boundaries for short and long vowel and consonant contrasts by Spanish-English bilingual listeners and English monolinguals. Listeners tended to adapt their perceptual boundaries to speech rates, but the strategy differed between groups, especially for consonants. Understanding the factors that influence auditory processing in this population is essential for developing appropriate assessments of auditory comprehension. These findings have implications for the clinical care of older populations whose ability to rely on spectral and/or temporal information in the auditory signal may decline.

Auditory discrimination in aging bilinguals vs. monolinguals with and without hearing loss.

Demands for effective assessments of speech perception specific to the aging brain are increasing, as the impacts of hearing loss on an individual's functional health, socialization, and cognition have become more widely recognized. Understanding the mechanisms behind the optimal function of the aging brain in relation to speech and language is challenging, especially in the bilingual population where the language learning and language interference processes could be mistaken for perceptual difficulty. Age-related presbycusis is unavoidable, and the contributions of this sensorineural hearing loss (SNHL) process on impaired speech recognition are not completely understood. This lack of understanding of the effects of aging and bilingual language competency on speech perception can act as a barrier to successful auditory rehabilitation. The present study investigated the effects of aging on vowel sound discrimination in adult listeners (age 50+) with the following characteristics: American English (AE) monolinguals with normal hearing, simultaneous or early sequential Spanish-English (SE) bilinguals with normal hearing, and AE monolinguals with SNHL (AE-SNHL). The goal was to identify the differences in vowel sound discrimination performance between the monolingual and bilingual aging populations to guide future language assessments and intervention processes. English vowel discrimination was assessed using an AXB discrimination task in quiet and using the Quick Speech in Noise (QuickSIN) test. SE bilinguals were outperformed by AE and AE-SNHL monolinguals, suggesting SE bilinguals primarily use their L1 acoustic properties to discriminate speech segments. No significant difference was found in QuickSIN performance between the bilingual and the monolingual groups, but there was a significant difference between AE and AE-SNHL. In conclusion, vowel discrimination was affected by interference with the native language, while performance in the noise condition was affected by hearing loss. The results of this study contribute to our understanding of the age-related speech processing deficits from three different aging groups regarding the cognitive control system.

Perception of temporally contrasted Japanese words by Spanish-English bilinguals and American English monolinguals.

Japanese and English use temporal cues within vowels, suggesting an audio-processing advantage for temporally-cued contrasts, while Spanish does not. Using a categorial AXB discrimination task, this study investigated how American English-speaking monolinguals and early and late Spanish-English bilinguals perceive three types of temporally-contrasting Japanese pairs: vowel length (kado/kaado), consonant length (iken/ikken), and syllable number (hjaku/hijaku). All groups performed worse than Japanese controls for the vowel length and syllable number contrasts, but only early bilinguals differed from controls for consonant length. This research contributes to a better understanding of how the first-learned language influences speech perception in a second language.

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

PURPOSE: 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. METHOD: 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. RESULTS: 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. CONCLUSION: The findings suggest initial feasibility of online assessment in this population and can inform selection of tests for auditory assessment of Spanish-English bilinguals.

Automaticity of speech processing in early bilingual adults and children.

We examine whether early acquisition of a second language (L2) leads to native-like neural processing of phonemic contrasts that are absent in the L1. Four groups (adult and child monolingual speakers of English; adult and child early bilingual speakers of English and Spanish, exposed to both languages before 5 years of age) participated in a study comparing the English /I/ - /ε/ contrast. Neural measures of automatic change detection (Mismatch Negativity, MMN) and attention (Processing Negativity, PN and Late Negativity, LN) were measured by varying whether participants tracked the stimulus stream or not. We observed no effect of bilingualism on the MMN, but adult bilinguals differed significantly from adult monolinguals on neural indices of attention. The child bilinguals were indistinguishable from their monolingual peers. This suggest that learning a L2 before five years of age leads to native-like phoneme discrimination, but bilinguals develop increased attentional sensitivity to speech sounds.

Second-language learning effects on automaticity of speech processing of Japanese phonetic contrasts: An MEG study.

We examined discrimination of a second-language (L2) vowel duration contrast in English learners of Japanese (JP) with different amounts of experience using the magnetoencephalography mismatch field (MMF) component. Twelve L2 learners were tested before and after a second semester of college-level JP; half attended a regular rate course and half an accelerated course with more hours per week. Results showed no significant change in MMF for either the regular or accelerated learning group from beginning to end of the course. We also compared these groups against nine L2 learners who had completed four semesters of college-level JP. These 4-semester learners did not significantly differ from 2-semester learners, in that only a difference in hemisphere activation (interacting with time) between the two groups approached significance. These findings suggest that targeted training of L2 phonology may be necessary to allow for changes in processing of L2 speech contrasts at an early, automatic level.

Neural measures of a Japanese consonant length discrimination by Japanese and American English listeners: Effects of attention.

This study examined automaticity of discrimination of a Japanese length contrast for consonants (miʃi vs. miʃʃi) in native (Japanese) and non-native (American-English) listeners using behavioral measures and the event-related potential (ERP) mismatch negativity (MMN). Attention to the auditory input was manipulated either away from the auditory input via a visual oddball task (Visual Attend), or to the input by asking the listeners to count auditory deviants (Auditory Attend). Results showed a larger MMN when attention was focused on the consonant contrast than away from it for both groups. The MMN was larger for consonant duration increments than decrements. No difference in MMN between the language groups was observed, but the Japanese listeners did show better behavioral discrimination than the American English listeners. In addition, behavioral responses showed a weak, but significant correlation with MMN amplitude. These findings suggest that both acoustic-phonetic properties and phonological experience affects automaticity of speech processing. This article is part of a Special Issue entitled SI: Prediction and Attention.

Cross-language perceptual similarity predicts categorial discrimination of American vowels by naïve Japanese listeners.

Current speech perception models propose that relative perceptual difficulties with non-native segmental contrasts can be predicted from cross-language phonetic similarities. Japanese (J) listeners performed a categorical discrimination task in which nine contrasts (six adjacent height pairs, three front/back pairs) involving eight American (AE) vowels [iː, ɪ, ε, æː, ɑː, ʌ, ʊ, uː] in /hVbə/ disyllables were tested. The listeners also completed a perceptual assimilation task (categorization as J vowels with category goodness ratings). Perceptual assimilation patterns (quantified as categorization overlap scores) were highly predictive of discrimination accuracy (r(s)=0.93). Results suggested that J listeners used both spectral and temporal information in discriminating vowel contrasts.

Perception of Japanese temporally-cued contrasts by American English listeners.

American listeners' perception of Japanese contrasts of vowel length (e.g., kiro vs. kiiro), consonant length (e.g., kite vs. kitte) and syllable number/length (e.g., k(j)oo vs. kijoo) was examined. Stimuli consisted of sentence-length utterances produced by a native Japanese talker; five minimal pairs of each contrast type were included. Questions were: a) can American listeners with no Japanese experience discriminate these contrasts, b) are there differences in relative difficulty of the three contrast types, and c) do instructions and other task variables affect performance accuracy? A categorial AXB discrimination task was used in two studies: Study I tested the three contrast types presented in separate blocks with detailed instructions about what to listen for; Study 2 tested the contrast types presented randomly intermixed with no specific instructions about the nature of the contrasts. Results indicated that naive American listeners could discriminate all three contrast types well above chance, and that there were no significant overall differences in relative difficulty across contrast types. Performance was significantly poorer in Study 2 where listeners' attention had not been directed to the nature of the contrasts. In both studies, there was significant and large variability in accuracy across different minimal pairs of each contrast type.

Perception of a Japanese vowel length contrast by Japanese and American English listeners: behavioral and electrophysiological measures.

This study examined the role of automatic selective perceptual processes in native and non-native listeners' perception of a Japanese vowel length contrast (tado vs. taado), using multiple, natural-speech tokens of each category as stimuli in a "categorial oddball" design. Mismatch negativity (MMN) was used to index discrimination of the temporally-cued vowel contrast by naïve adult American listeners and by a native Japanese-speaking control group in two experiments in which attention to the auditory input was manipulated: in Exp 1 (Visual-Attend), listeners silently counted deviants in a simultaneously-presented visual categorial oddball shape discrimination task; in Exp 2 (Auditory-Attend), listeners attended to the auditory input and implicitly counted target deviants. MMN results showed effects of language experience and attentional focus: MMN amplitudes were smaller for American compared to Japanese listeners in the Visual-Attend Condition and for the American listeners in the Visual compared to Auditory-Attend Condition. Subtle differences in topography were also seen, specifically in that the Japanese group showed more robust responses than the American listeners at left hemisphere scalp sites that probably index activity from the superior temporal gyrus. Follow-up behavioral discrimination tests showed that Americans discriminated the contrast well above chance, but more poorly than did Japanese listeners. This pattern of electrophysiological and behavioral results supports the conclusion that early experience with phonetic contrasts of a language results in changes in neural representations in the auditory cortex that allow for more robust automatic, phonetic processing of native-language speech input.

Acoustic variability within and across German, French, and American English vowels: phonetic context effects.

Cross-language perception studies report influences of speech style and consonantal context on perceived similarity and discrimination of non-native vowels by inexperienced and experienced listeners. Detailed acoustic comparisons of distributions of vowels produced by native speakers of North German (NG), Parisian French (PF) and New York English (AE) in citation (di)syllables and in sentences (surrounded by labial and alveolar stops) are reported here. Results of within- and cross-language discriminant analyses reveal striking dissimilarities across languages in the spectral/temporal variation of coarticulated vowels. As expected, vocalic duration was most important in differentiating NG vowels; it did not contribute to PF vowel classification. Spectrally, NG long vowels showed little coarticulatory change, but back/low short vowels were fronted/raised in alveolar context. PF vowels showed greater coarticulatory effects overall; back and front rounded vowels were fronted, low and mid-low vowels were raised in both sentence contexts. AE mid to high back vowels were extremely fronted in alveolar contexts, with little change in mid-low and low long vowels. Cross-language discriminant analyses revealed varying patterns of spectral (dis)similarity across speech styles and consonantal contexts that could, in part, account for AE listeners' perception of German and French front rounded vowels, and "similar" mid-high to mid-low vowels.