Testing the double phonemic boundary in bilinguals

The effect of native language and bilingualism on multimodal perception in speech: A study of audio-aerotactile integrationa)

Previous studies of speech perception revealed that tactile sensation can be integrated into the perception of stop consonants. It remains uncertain whether such multisensory integration can be shaped by linguistic experience, such as the listener's native language(s). This study investigates audio-aerotactile integration in phoneme perception for English and French monolinguals as well as English-French bilingual listeners. Six step voice onset time continua of alveolar (/da/-/ta/) and labial (/ba/-/pa/) stops constructed from both English and French end points were presented to listeners who performed a forced-choice identification task. Air puffs were synchronized to syllable onset and randomly applied to the back of the hand. Results show that stimuli with an air puff elicited more "voiceless" responses for the /da/-/ta/ continuum by both English and French listeners. This suggests that audio-aerotactile integration can occur even though the French listeners did not have an aspiration/non-aspiration contrast in their native language. Furthermore, bilingual speakers showed larger air puff effects compared to monolinguals in both languages, perhaps due to bilinguals' heightened receptiveness to multimodal information in speech.

Early linguistic experience shapes bilingual adults' hearing for phonemes in both languages

English and Mandarin Chinese differ in the voice onset times (VOTs) of /b/ and /p/. Hence the way bilinguals perceive these sounds may show 'tuning' to the language-specific acoustic structure of a bilingual's languages (a discrete model), or a shared representation across languages (a unitary model). We investigated whether an individual's early childhood exposure influences their model of phoneme perception across languages, in a large sample of early English-Mandarin bilingual adults in Singapore (N = 66). As preregistered, we mapped identification functions on a /b/-/p/ VOT continuum in each language. Bilingual balance was estimated using principal components analysis and entered into GLMMs of phoneme boundary and slope. VOT boundaries were earlier for English than Mandarin, and bilingual balance predicted the slope of the transition between categories across both languages: Those who heard more English from an earlier age showed steeper category boundaries than those who heard more Mandarin, suggesting early bilinguals may transfer their model for how phonemes differ from their earlier/stronger languages to later/weaker languages. We describe the transfer model of discrete phoneme representations and its implications for use of the phoneme identification task in diverse populations.

Crosslinguistic Influence in the Discrimination of Korean Stop Contrast by Heritage Speakers and Second Language Learners

The present study examines the extent of crosslinguistic influence from English as a dominant language in the perception of the Korean lenis–aspirated contrast among Korean heritage speakers in the United States (N = 20) and English-speaking learners of Korean as a second language (N = 20), as compared to native speakers of Korean immersed in the first language environment (N = 20), by using an AX discrimination task. In addition, we sought to determine whether significant dependencies could be observed between participants’ linguistic background and experiences and their perceptual accuracy in the discrimination task. Results of a mixed-effects logistic regression model demonstrated that heritage speakers outperformed second language learners with 85% vs. 63% accurate discrimination, while no significant difference was detected between heritage speakers and first language-immersed native speakers (85% vs. 88% correct). Furthermore, higher verbal fluency was significantly predictive of greater perceptual accuracy for the heritage speakers. The results are compatible with the interpretation that the influence of English on the discrimination of the Korean laryngeal contrast was stronger for second language learners of Korean than for heritage speakers, while heritage speakers were not apparently affected by dominance in English in their discrimination of Korean lenis and aspirated stops.

An analysis of the perception of stop consonants in bilinguals and monolinguals in different phonetic contexts: A range-based language cueing approach

Bilinguals' observed perceptual shift across language contexts for shared acoustic properties between their languages supports the idea that bilinguals, but not monolinguals, develop two phonemic representations for the same acoustic property. This phenomenon is known as the double phonemic boundary. This investigation replicated previous findings of bilinguals' double phonemic boundary across a series of go/no-go tasks while controlling for known confounding effects in speech perception (i.e., contrast effects) and differences in resource allocation between bilinguals and monolinguals (i.e., left-hand or right-hand response). Using a range-base language cueing approach, we designed 2 experiments. The first experiment tested whether a voice onset time (VOT) range representative of either Spanish or English phonetic categories can cue bilinguals, but not monolinguals, to use language-specific perceptual routines. The second experiment tested a VOT range with a mixture of Spanish and English phonetic categories to determine whether directing attention to a specific phonetic category can disambiguate the competition of the nonattended category. The results for Experiment 1 showed that bilinguals can rely on the distributional patterns of their native phonetic categories to activate specific language modes. Experiment 2 showed that attention can change the weight given to a native phonetic distinction. However, this process is restricted by the internal phonetic composition of the native language(s).

How bilinguals perceive speech depends on which language they think they're hearing

Bilinguals understand when the communication context calls for speaking a particular language and can switch from speaking one language to speaking the other based on such conceptual knowledge. There is disagreement regarding whether conceptually-based language selection is also possible in the listening modality. For example, can bilingual listeners perceptually adjust to changes in pronunciation across languages based on their conceptual understanding of which language they're currently hearing? We asked French- and Spanish-English bilinguals to identify nonsense monosyllables as beginning with /b/ or /p/, speech categories that French and Spanish speakers pronounce differently than English speakers. We conceptually cued each bilingual group to one of their two languages or the other by explicitly instructing them that the speech items were word onsets in that language, uttered by a native speaker thereof. Both groups adjusted their /b-p/ identification boundary as a function of this conceptual cue to the language context. These results support a bilingual model permitting conceptually-based language selection on both the speaking and listening end of a communicative exchange.

Phonetic drift in Spanish-English bilinguals: Experiment and a self-organizing model

Studies of speech accommodation provide evidence for change in use of language structures beyond the critical/sensitive period. For example, Sancier and Fowler (1997) found changes in the voice-onset-times (VOTs) of both languages of a Portuguese-English bilingual as a function of her language context. Though accommodation has been studied widely within a monolingual context, it has received less attention in and between the languages of bilinguals. We tested whether these findings of phonetic accommodation, speech accommodation at the phonetic level, would generalize to a sample of Spanish-English bilinguals. We recorded participants reading Spanish and English sentences after 3-4 months in the US and after 2-4 weeks in a Spanish speaking country and measured the VOTs of their voiceless plosives. Our statistical analyses show that participants' English VOTs drifted towards those of the ambient language, but their Spanish VOTs did not. We found considerable variation in the extent of individual participants' drift in English. Further analysis of our results suggested that native-likeness of L2 VOTs and extent of active language use predict the extent of drift. We provide a model based on principles of self-organizing dynamical systems to account for our Spanish-English phonetic drift findings and the Portuguese-English findings.

The Effects of Language Experience and Speech Context on the Phonetic Accommodation of English-accented Spanish Voicing

Native speakers of Spanish with different amounts of experience with English classified stop-consonant voicing (/b/ versus /p/) across different speech accents: English-accented Spanish, native Spanish, and native English. While listeners with little experience with English classified target voicing with an English- or Spanish-like voice onset time (VOT) boundary, predicted by contextual VOT, listeners familiar with English relied on an English-like VOT boundary in an English-accented Spanish context even in the absence of clear contextual cues to English VOT. This indicates that Spanish listeners accommodated English-accented Spanish voicing differently depending on their degree of familiarization with the English norm.

Mandarin-English Bilinguals Process Lexical Tones in Newly Learned Words in Accordance with the Language Context

Previous research has mainly considered the impact of tone-language experience on ability to discriminate linguistic pitch, but proficient bilingual listening requires differential processing of sound variation in each language context. Here, we ask whether Mandarin-English bilinguals, for whom pitch indicates word distinctions in one language but not the other, can process pitch differently in a Mandarin context vs. an English context. Across three eye-tracked word-learning experiments, results indicated that tone-intonation bilinguals process tone in accordance with the language context. In Experiment 1, 51 Mandarin-English bilinguals and 26 English speakers without tone experience were taught Mandarin-compatible novel words with tones. Mandarin-English bilinguals out-performed English speakers, and, for bilinguals, overall accuracy was correlated with Mandarin dominance. Experiment 2 taught 24 Mandarin-English bilinguals and 25 English speakers novel words with Mandarin-like tones, but English-like phonemes and phonotactics. The Mandarin-dominance advantages observed in Experiment 1 disappeared when words were English-like. Experiment 3 contrasted Mandarin-like vs. English-like words in a within-subjects design, providing even stronger evidence that bilinguals can process tone language-specifically. Bilinguals (N = 58), regardless of language dominance, attended more to tone than English speakers without Mandarin experience (N = 28), but only when words were Mandarin-like-not when they were English-like. Mandarin-English bilinguals thus tailor tone processing to the within-word language context.

Neuroimaging of the bilingual brain: Structural brain correlates of listening and speaking in a second language

Diffusion tensor imaging was used to compare white matter structure between American monolingual and Spanish-English bilingual adults living in the United States. In the bilingual group, relationships between white matter structure and naturalistic immersive experience in listening to and speaking English were additionally explored. White matter structural differences between groups were found to be bilateral and widespread. In the bilingual group, experience in listening to English was more robustly correlated with decreases in radial and mean diffusivity in anterior white matter regions of the left hemisphere, whereas experience in speaking English was more robustly correlated with increases in fractional anisotropy in more posterior left hemisphere white matter regions. The findings suggest that (a) foreign language immersion induces neuroplasticity in the adult brain, (b) the degree of alteration is proportional to language experience, and (c) the modes of immersive language experience have more robust effects on different brain regions and on different structural features.

Limits on Monolingualism? A Comparison of Monolingual and Bilingual Infants' Abilities to Integrate Lexical Tone in Novel Word Learning

To construct their first lexicon, infants must determine the relationship between native phonological variation and the meanings of words. This process is arguably more complex for bilingual learners who are often confronted with phonological conflict: phonological variation that is lexically relevant in one language may be lexically irrelevant in the other. In a series of four experiments, the present study investigated English-Mandarin bilingual infants' abilities to negotiate phonological conflict introduced by learning both a tone and a non-tone language. In a novel word learning task, bilingual children were tested on their sensitivity to tone variation in English and Mandarin contexts. Their abilities to interpret tone variation in a language-dependent manner were compared to those of monolingual Mandarin learning infants. Results demonstrated that at 12-13 months, bilingual infants demonstrated the ability to bind tone to word meanings in Mandarin, but to disregard tone variation when learning new words in English. In contrast, monolingual learners of Mandarin did not show evidence of integrating tones into word meanings in Mandarin at the same age even though they were learning a tone language. However, a tone discrimination paradigm confirmed that monolingual Mandarin learning infants were able to tell these tones apart at 12-13 months under a different set of conditions. Later, at 17-18 months, monolingual Mandarin learners were able to bind tone variation to word meanings when learning new words. Our findings are discussed in terms of cognitive adaptations associated with bilingualism that may ease the negotiation of phonological conflict and facilitate precocious uptake of certain properties of each language.

Can bilingual children turn one language off? Evidence from perceptual switching

Bilinguals have the sole option of conversing in one language in spite of knowing two languages. The question of how bilinguals alternate between their two languages, activating and deactivating one language, is not well understood. In the current study, we investigated the development of this process by researching bilingual children's abilities to selectively integrate lexical tone based on its relevance in the language being used. In particular, the current study sought to determine the effects of global conversation-level cues versus local (within-word phonotactic) cues on children's tone integration in newly learned words. Words were taught to children via a conversational narrative, and word recognition was investigated using the intermodal preferential-looking paradigm. Children were tested on recognition of words with stimuli that were either matched or mismatched in tone in both English and Mandarin conversations. Results demonstrated that 3- to 4-year-olds did not adapt their interpretation of lexical tone changes to the language being spoken. In contrast, 4- to 5-year-olds were able to do so when supported by informative within-word cues. Results suggest that preschool children are capable of selectively activating a single language given word-internal cues to language.

Effects of language experience and expectations on attention to consonants and tones in English and Mandarin Chinese

Both long-term native language experience and immediate linguistic expectations can affect listeners' use of acoustic information when making a phonetic decision. In this study, a Garner selective attention task was used to investigate differences in attention to consonants and tones by American English-speaking listeners (N = 20) and Mandarin Chinese-speaking listeners hearing speech in either American English (N = 17) or Mandarin Chinese (N = 20). To minimize the effects of lexical differences and differences in the linguistic status of pitch across the two languages, stimuli and response conditions were selected such that all tokens constitute legitimate words in both languages and all responses required listeners to make decisions that were linguistically meaningful in their native language. Results showed that regardless of ambient language, Chinese listeners processed consonant and tone in a combined manner, consistent with previous research. In contrast, English listeners treated tones and consonants as perceptually separable. Results are discussed in terms of the role of sub-phonemic differences in acoustic cues across language, and the linguistic status of consonants and pitch contours in the two languages.

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.

Auditory enhancement and second language experience in Spanish and English weighting of secondary voicing cues

The role of secondary cues in voicing categorization was investigated in three listener groups: Monolingual English (n = 20) and Spanish speakers (n = 20), and Spanish speakers with significant English experience (n = 16). Results showed that, in all three groups, participants used onset f0 in making voicing decisions only in the positive voice onset time (VOT) range (short lag and long lag tokens), while there was no effect of onset f0 on voicing categorization within the negative VOT range (voicing lead tokens) for any of the participant groups. These results support an auditory enhancement view of perceptual cue weighting: Onset f0 serves as a secondary cue to voicing only in the positive VOT range where it is not overshadowed by the presence of pre-voicing. Moreover, results showed that Spanish learners of English gave a significantly greater weight to onset f0 in their voicing decisions than did listeners in either of the other two groups. This result supports the view that learners may overweight secondary cues to distinguish between non-native categories that are assimilated to the same native category on the basis of a primary cue.

Focusing the lens of language experience: perception of Ma'di stops by Greek and English bilinguals and monolinguals

Monolingual listeners are constrained by native language experience when categorizing and discriminating unfamiliar non-native contrasts. Are early bilinguals constrained in the same way by their two languages, or do they possess an advantage? Greek-English bilinguals in either Greek or English language mode were compared to monolinguals on categorization and discrimination of Ma'di stop-voicing distinctions that are non-native to both languages. As predicted, English monolinguals categorized Ma'di prevoiced plosive and implosive stops and the coronal voiceless stop as English voiced stops. The Greek monolinguals categorized the Ma'di short-lag voiceless stops as Greek voiceless stops, and the prevoiced implosive stops and the coronal prevoiced stop as Greek voiced stops. Ma'di prenasalized stops were uncategorized. Greek monolinguals discriminated the non-native voiced-voiceless contrasts very well, whereas the English monolinguals did poorly. Bilinguals were given all oral and written instructions either in English or in Greek (language mode manipulation). Each language mode subgroup categorized Ma'di stop-voicing comparably to the corresponding monolingual group. However, the bilinguals' discrimination was unaffected by language mode: both subgroups performed intermediate to the monolinguals for the prevoiced-voiceless contrast. Thus, bilinguals do not possess an advantage for unfamiliar non-native contrasts, but are nonetheless uniquely configured language users, differing from either monolingual group.

Two ways to listen: Do L2-dominant bilinguals perceive stop voicing according to language mode?

How listeners categorize two phones predicts the success with which they will discriminate the given phonetic distinction. In the case of bilinguals, such perceptual patterns could reveal whether the listener's two phonological systems are integrated or separate. This is of particular interest when a given contrast is realized differently in each language, as is the case with Greek and English stop-voicing distinctions. We had Greek-English early sequential bilinguals and Greek and English monolinguals (baselines) categorize, rate, and discriminate stop-voicing contrasts in each language. All communication with each group of bilinguals occurred solely in one language mode, Greek or English. The monolingual groups showed the expected native-language constraints, each perceiving their native contrast more accurately than the opposing nonnative contrast. Bilinguals' category-goodness ratings for the same physical stimuli differed, consistent with their language mode, yet their discrimination performance was unaffected by language mode and biased toward their dominant language (English). We conclude that bilinguals integrate both languages in a common phonetic space that is swayed by their long-term dominant language environment for discrimination, but that they selectively attend to language-specific phonetic information for phonologically motivated judgments (category-goodness ratings).

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.