Discrimination of coronal stops by bilingual adults: the timing and nature of language interaction

The effect of background noise on speech perception in monolingual and bilingual adults with normal hearing

Background

Previous studies have highlighted that bilingual listeners have a deficit in speech perception in their second language compared with monolingual listeners in noisy listening environments. This deficit may give rise to educational and occupational implications for bilingual speakers who are studying or working in non-native language environments in poor acoustic conditions.

Objectives

To compare the speech perception performance of monolingual English speakers and English as a second language (ESL) bilinguals within environments with various levels of background noise and to examine whether bilinguals with an early age of second language acquisition would perform better than those with a late age of acquisition.

Study sample

Two groups of adult listeners with normal hearing participated: monolingual British English listeners (N = 15) and bilingual Arabic listeners for whom English was their second language and who were proficient in English (N = 15). The quick speech-in-noise (QuickSIN) test was used to assess signal-to-noise ratio (SNR) loss and SNR-50 for both groups.

Results

The QuickSIN test results indicated that bilingual Arabic listeners with normal hearing displayed a mild SNR loss comparable to that observed for a person with hearing loss, indicating a higher SNR needed for this population to achieve a comparable level of comprehension to their monolingual English peers.

Conclusion

Results highlight the importance of measuring SNR loss to obtain accurate diagnosis and potential rehabilitative information that is not available from audiogram studies.

Between Äh(m) and Euh(m): The Distribution and Realization of Filled Pauses in the Speech of German-French Simultaneous Bilinguals

Filled pauses are well known for their speaker specificity, yet cross-linguistic research has also shown language-specific trends in their distribution and phonetic quality. To examine the extent to which speakers acquire filled pauses as language- or speaker-specific phenomena, this study investigates the use of filled pauses in the context of adult simultaneous bilinguals. Making use of both distributional and acoustic data, this study analyzed UH, consisting of only a vowel component, and UM, with a vowel followed by [m], in the speech of 15 female speakers who were simultaneously bilingual in French and German. Speakers were found to use UM more frequently in German than in French, but only German-dominant speakers had a preference for UM in German. Formant and durational analyses showed that while speakers maintained distinct vowel qualities in their filled pauses in different languages, filled pauses in their weaker language exhibited a shift towards those in their dominant language. These results suggest that, despite high levels of variability between speakers, there is a significant role for language in the acquisition of filled pauses in simultaneous bilingual speakers, which is further shaped by the linguistic environment they grow up in.

Phonetic Category Formation is Perceptually Driven During the Early Stages of Adult L2 Development

Research on the acquisition of L2 phonology in sequential language learners has stressed the importance of language use and input as a means to accurate production and perception; however, the two constructs are difficult to evaluate and control. This study focuses on the role of language use during the initial stages of development of phonetic categories related to stop voicing and analyzes the relationship between production and perception. Native English-speaking late learners of Spanish provided production/perception data on a weekly basis throughout the course of a seven-week immersion program in which L1 use was prohibited. The production/perception data were analyzed using generalized linear mixed effects models. Generalized additive mixed models were used to analyze and compare the learning trajectories of each modality. The analyses revealed phonetic learning in both production and perception over the course of the program. Perception gains paralleled those of native bilinguals by the conclusion of the program and preceded production gains. This study is novel in that it provides production/perception data in a semi-longitudinal design. Moreover, the beginning adult learners are examined in a learning context in which L1 use was minimal and L2 input was maximized. Taken together, the experiments suggest that L2 phonetic category formation can occur abruptly, at an early stage of development, is perceptually driven, and appears to be particularly fragile during the initial stages of learning.

Neural Indices of Vowel Discrimination in Monolingual and Bilingual Infants and Children

OBJECTIVES

To examine maturation of neural discriminative responses to an English vowel contrast from infancy to 4 years of age and to determine how biological factors (age and sex) and an experiential factor (amount of Spanish versus English input) modulate neural discrimination of speech.

DESIGN

Event-related potential (ERP) mismatch responses (MMRs) were used as indices of discrimination of the American English vowels [ε] versus [I] in infants and children between 3 months and 47 months of age. A total of 168 longitudinal and cross-sectional data sets were collected from 98 children (Bilingual Spanish-English: 47 male and 31 female sessions; Monolingual English: 48 male and 42 female sessions). Language exposure and other language measures were collected. ERP responses were examined in an early time window (160 to 360 msec, early MMR [eMMR]) and late time window (400 to 600 msec, late MMR).

RESULTS

The eMMR became more negative with increasing age. Language experience and sex also influenced the amplitude of the eMMR. Specifically, bilingual children, especially bilingual females, showed more negative eMMR compared with monolingual children and with males. However, the subset of bilingual children with more exposure to English than Spanish compared with those with more exposure to Spanish than English (as reported by caretakers) showed similar amplitude of the eMMR to their monolingual peers. Age was the only factor that influenced the amplitude of the late MMR. More negative late MMR was observed in older children with no difference found between bilingual and monolingual groups.

CONCLUSIONS

Consistent with previous studies, our findings revealed that biological factors (age and sex) and language experience modulated the amplitude of the eMMR in young children. The early negative MMR is likely to be the mismatch negativity found in older children and adults. In contrast, the late MMR amplitude was influenced only by age and may be equivalent to the Nc in infants and to the late negativity observed in some auditory passive oddball designs.

Perception of English phonetic contrasts by Dutch children: How bilingual are early-English learners?

The aim of this study was to investigate whether early-English education benefits the perception of English phonetic contrasts that are known to be perceptually confusable for Dutch native speakers, comparing Dutch pupils who were enrolled in an early-English programme at school from the age of four with pupils in a mainstream programme with English instruction from the age of 11, and English-Dutch early bilingual children. Children were 4-5-year-olds (start of primary school), 8-9-year-olds, or 11-12-year-olds (end of primary school). Children were tested on four contrasts that varied in difficulty: /b/-/s/ (easy), /k/-/ɡ/ (intermediate), /f/-/θ/ (difficult), /ɛ/-/æ/ (very difficult). Bilingual children outperformed the two other groups on all contrasts except /b/-/s/. Early-English pupils did not outperform mainstream pupils on any of the contrasts. This shows that early-English education as it is currently implemented is not beneficial for pupils' perception of non-native contrasts.

Phonological Vulnerability for School-Aged Spanish-English-Speaking Bilingual Children

This study examined accuracy on syllable-final (coda) consonants in newly-learned English-like nonwords to determine whether school-aged bilingual children may be more vulnerable to making errors on English-only codas than their monolingual, English-speaking peers, even at a stage in development when phonological accuracy in productions of familiar words is high. Bilingual Spanish-English-speaking second- graders (age 7-9) with typical development (n=40) were matched individually with monolingual peers on age, sex, and speech skills. Participants learned to name sea monsters as part of five computerized word learning tasks. Dependent t-tests revealed bilingual children were less accurate than monolingual children in producing codas unique to English; however, the groups demonstrated equivalent levels of accuracy on codas that occur in both Spanish and English. Results suggest that, even at high levels of English proficiency, bilingual Spanish-English-speaking children may demonstrate lower accuracy than their monolingual English-speaking peers on targets that pattern differently in their two languages. Differences between a bilingual's two languages can be used to reveal targets that may be more vulnerable to error, which could be a result of cross-linguistic effects or more limited practice with English phonology.

Cross-linguistic vowel variation in trilingual speakers of Saterland Frisian, Low German, and High German

The present study compares the acoustic realization of Saterland Frisian, Low German, and High German vowels by trilingual speakers in the Saterland. The Saterland is a rural municipality in northwestern Germany. It offers the unique opportunity to study trilingualism with languages that differ both by their vowel inventories and by external factors, such as their social status and the autonomy of their speech communities. The objective of the study was to examine whether the trilingual speakers differ in their acoustic realizations of vowel categories shared by the three languages and whether those differences can be interpreted as effects of either the differences in the vowel systems or of external factors. Monophthongs produced in a /hVt/ frame revealed that High German vowels show the most divergent realizations in terms of vowel duration and formant frequencies, whereas Saterland Frisian and Low German vowels show small differences. These findings suggest that vowels of different languages are likely to share the same phonological space when the speech communities largely overlap, as is the case with Saterland Frisian and Low German, but may resist convergence if at least one language is shared with a larger, monolingual speech community, as is the case with High German.

Production and Perception of the /i/-/I/ Vowel Contrast: The Case of L2-Dominant Early Learners of English

The present study explored the production and perception of the /i/-/I/ vowel contrast in second language (L2)-dominant early learners of American English who no longer fluently speak their first language (L1, Spanish). The production task analyzed the extent to which the early learner group differed from controls (native English speakers and L1-Spanish late-onset learners of English) with regard to duration and spectral centroids. The perception experiment examined how these early learners classified resynthesized stimuli drawn from the /i/-/I/ contrast using distinct acoustic cues - spectral and temporal - in a 2-alternative forced choice identification task. The first experiment revealed that the early learners produced the contrast in a native-like manner in terms of the spectral envelope and duration use. The second experiment found that early learners differed from both control groups in how they categorized the /i/-/I/ continua based on spectrum and duration, and the extent to which they rely on these two cues. The effects of linguistic experience on L2 phonetic behavior are discussed.

Discrimination of Multiple Coronal Stop Contrasts in Wubuy (Australia): A Natural Referent Consonant Account

Native speech perception is generally assumed to be highly efficient and accurate. Very little research has, however, directly examined the limitations of native perception, especially for contrasts that are only minimally differentiated acoustically and articulatorily. Here, we demonstrate that native speech perception may indeed be more difficult than is often assumed, where phonemes are highly similar, and we address the nature and extremes of consonant perception. We present two studies of native and non-native (English) perception of the acoustically and articulatorily similar four-way coronal stop contrast /t ʈ [symbol: see text] ȶ/ (apico-alveolar, apico-retroflex, lamino-dental, lamino-alveopalatal) of Wubuy, an indigenous language of Australia. The results show that all listeners find contrasts involving /ȶ/ easy to discriminate, but that, for both groups, contrasts involving /t ʈ [symbol: see text]/ are much harder. Where the two groups differ, the results largely reflect native language (Wubuy vs English) attunement as predicted by the Perceptual Assimilation Model. We also observe striking perceptual asymmetries in the native listeners' perception of contrasts involving the latter three stops, likely due to the differences in input frequency. Such asymmetries have not previously been observed in adults, and we propose a novel Natural Referent Consonant Hypothesis to account for the results.

Fine-grained and probabilistic cross-linguistic influence in the pronunciation of cognates: Evidence from corpus-based spontaneous conversation and experimentally elicited data

The present study examines variable realizations of Spanish word-initial voiced and voiceless dental stops in Spanish-English cognate pairs. Employing a variationist approach to naturalistic data, we report significantly decreased likelihood of reduced articulations of word-initial /d/ in cognates in spontaneous bilingual Puerto Rican discourse, and no such probabilistic effect for cognates in monolingual Spanish of the same speech community. Using experimentally controlled elicited data of Spanish word-initial /t/, we also find evidence of significant fine-grained effects of English on the articulations of Spanish cognates in the form of lengthened VOT for Spanish-English bilinguals. These results indicate that cross-language lexical connections affect phonetic categories in the speech production of Spanish-English bilinguals. It is proposed that both fine-grained and probabilistic effects of the phonology of one language on another can be explained within the Exemplar Model of Lexical Representation.

The perception of the French /s/-/ʃ/ contrast in early Creole-French bilinguals

One particularity of the Mauritian Creole language is that there is no contrastive distinction between the consonants /s/ and /ʃ/, which are both pronounced /s/ in Creole. In this study, we examined the identification performance of the /s/-/ʃ/ contrast by Mauritian Creole-French bilinguals who have been exposed to French before 7 years of age, and who have been raised in a highly Creole-French bilingual society. The results showed that most of our bilingual participants identify the /s/ and /ʃ/ consonants like native French speakers. It also appeared that the way in which the two consonants are categorized can be manipulated by introducing subtle changes in the information these participants were given about the identity of the speaker that produced the stimuli. Our results are in accordance with recent studies showing native-like performance in bilinguals on a categorization task and, importantly, extend these findings to speakers of a Creole language. In addition, these results show that speech sound categorization can be influenced by information about the speaker's social identity and thus argue for models that postulate rich speech sound representations.

Bilingualism and auditory processing abilities: performance of adults in dichotic listening tests

Purpose: To evaluate and compare the dichotic listening abilities in non-hearing-impaired adults monolingual speakers of the Brazilian Portuguese language (CG) and simultaneous Brazilian Portuguese-German (GG) bilingual speakers or successive Brazilian Portuguese-Italian bilingual speakers (IG). Methods: This is about an observational, descriptive, transverse and quantitative research. The sample consisted of 87 subjects aged between 18 and 55 years, divided into: Control Group (CG), of 30 monolingual speakers of Brazilian Portuguese; Study Group A (SGA), of 31 simultaneous Brazilian Portuguese-German bilingual speakers; and Study Group I (SGI), of 26 successive Brazilian Portuguese-Italian speakers. The individuals were submitted to the Dichotic digits test (DDT) and to Staggered Spondaic Words (SSW). Results: The DTT results showed difference in right ear and total scores when comparing SGA to CG. Comparing the CG and the SGI, it was observed difference in right and left ears and total scores. Comparing the SGA and the SGI, no difference was observed between the groups. Results of SSW showed that both bilingual groups were significantly better in the right and left ears scores and even in total one when compared to CG. Comparing the SGA and the SGI, the SGI showed better significant scores in the right ear and total. Conclusion: Bilingual experiences seem to influence positively the ability of high predictability dichotic listening, evaluated by DDT, and the low predictability dichotic listening, evaluated by SSW test. The SSW results also showed statistically significantly better results for successive Brazilian Portuguese-Italian bilingual speakers when compared to simultaneous Brazilian Portuguese-German speakers.

Perceptual narrowing in the context of increased variation: Insights from bilingual infants

Human infants become native-language listeners through a process of perceptual narrowing. Monolingual infants are initially sensitive to a wide range of language-relevant contrasts. However, as they mature and gain native-language experience, their sensitivity to nonnative contrasts declines. Here, we consider the case of infants growing up bilingual as a window into how increased variation affects early perceptual development. These infants encounter different meaningful contrasts in each of their languages, and must also attend to contrasts that occur between their languages. Bilingual infants share many classic developmental patterns with monolinguals. However, they also show unique developmental patterns in the perception of native distinctions such as U-shaped trajectories and dose-response relationships, and show some enhanced sensitivity to nonnative distinctions. Analogous developmental patterns can be observed in individuals exposed to two nonlinguistic systems in domains such as music and face perception. Some preliminary evidence suggests that bilingual individuals might retain more sensitivity to nonnative contrasts, reaching a less narrow end state than monolinguals. Nevertheless, bilingual infants do become perceptually specialized native listeners to both of their languages, despite increased variation and differing patterns of perceptual development in comparison to monolinguals.

A Bafri, un Pafri

Bilinguals perceptually accommodate speech variation across languages, but to what extent this flexibility depends on bilingual experience is uncertain. One account suggests that bilingual experience promotes language-specific processing modes, implying that bilinguals can switch as appropriate between the different phonetic systems of the languages they speak. Another account suggests that bilinguals rapidly recalibrate to the unique acoustic properties of each language following language-general processes common to monolinguals. Challenging this latter account, the present results show that Spanish-English bilinguals with exposure to both languages from early childhood, but not English monolinguals, shift perception as appropriate across acoustically controlled English and Spanish contexts. Early bilingual experience appears to promote language-specific phonetic systems.

Assessing the double phonemic representation in bilingual speakers of Spanish and English: an electrophysiological study

Event Related Potentials (ERPs) were recorded from Spanish-English bilinguals (N=10) to test pre-attentive speech discrimination in two language contexts. ERPs were recorded while participants silently read magazines in English or Spanish. Two speech contrast conditions were recorded in each language context. In the phonemic in English condition, the speech sounds represented two different phonemic categories in English, but represented the same phonemic category in Spanish. In the phonemic in Spanish condition, the speech sounds represented two different phonemic categories in Spanish, but represented the same phonemic categories in English. Results showed pre-attentive discrimination when the acoustics/phonetics of the speech sounds match the language context (e.g., phonemic in English condition during the English language context). The results suggest that language contexts can affect pre-attentive auditory change detection. Specifically, bilinguals' mental processing of stop consonants relies on contextual linguistic information.

Bilingual beginnings to learning words

At the macrostructure level of language milestones, language acquisition follows a nearly identical course whether children grow up with one or with two languages. However, at the microstructure level, experimental research is revealing that the same proclivities and learning mechanisms that support language acquisition unfold somewhat differently in bilingual versus monolingual environments. This paper synthesizes recent findings in the area of early bilingualism by focusing on the question of how bilingual infants come to apply their phonetic sensitivities to word learning, as they must to learn minimal pair words (e.g. 'cat' and 'mat'). To this end, the paper reviews antecedent achievements by bilinguals throughout infancy and early childhood in the following areas: language discrimination and separation, speech perception, phonetic and phonotactic development, word recognition, word learning and aspects of conceptual development that underlie word learning. Special consideration is given to the role of language dominance, and to the unique challenges to language acquisition posed by a bilingual environment.

Developmental shift in the discrimination of vowel contrasts in bilingual infants: is the distributional account all there is to it?

A shift from language-general to language-specific sound discrimination abilities has been largely attested in different populations of infants during the second half of the first year of life; however, data are still scarce regarding bilingual populations. Previous research with 4-, 8- and 12-month-old Catalan-Spanish bilingual infants had offered evidence of a U-shaped pattern in their ability to discriminate a language-specific vowel contrast. This research explores monolingual and bilingual 4- and 8-month-olds' capacities to discriminate two common vowel contrasts: /o-u/ and /e-u/. All groups succeeded except 8-month-old bilinguals tested on the phonetically close /o-u/ contrast. Discrimination was not facilitated when talker and token variability were reduced. A U-shaped pattern was again found when data from an additional group of 12-month-olds were included. These results confirm bilinguals' specific developmental pattern of perceptual reorganization for acoustically close vowels and challenge an interpretation merely based on a distributional account.

Testing the double phonemic boundary in bilinguals

It is widely known that language influences the way speech sounds are categorized. However, categorization of speech sounds by bilinguals is not well understood. There is evidence that bilinguals have different category boundaries than monolinguals, and there is evidence suggesting that bilinguals' phonemic boundaries can shift with language context. This phenomenon has been referred as the double phonemic boundary. In this investigation, the double phonemic boundary is tested in Spanish-English bilinguals (N = 18) and English monolinguals (N = 16). Participants were asked to categorize speech stimuli from a continuum ranging from /ga/ to /ka/ in two language contexts. The results showed phonemic boundary shifts in bilinguals and monolinguals which did not differ across language contexts. However, the magnitude of the phoneme boundary shift was significantly correlated with the level of confidence in using English and Spanish (reading, writing, speaking, and comprehension) for bilinguals, but not for monolinguals. The challenges of testing the double phonemic boundary are discussed, along with the limitations of the methodology used in this study.

Development of coronal stop perception: bilingual infants keep pace with their monolingual peers

Previous studies indicate that the discrimination of native phonetic contrasts in infants exposed to two languages from birth follows a different developmental time course from that observed in monolingual infants. We compared infant discrimination of dental (French) and alveolar (English) place variants of /d/ in three groups differing in language experience. At 6-8 months, infants in all three language groups succeeded; at 10-12 months, monolingual English and bilingual but not monolingual French infants distinguished this contrast. Thus, for highly frequent, similar phones, despite overlap in cross-linguistic distributions, bilingual infants performed on par with their English monolingual peers and better than their French monolingual peers.