Left-hemisphere language lateralization in bilinguals: use of the concurrent activities paradigm

Previous visual and auditory lateralization studies have demonstrated that the languages of bilinguals are lateralized to the left hemisphere to the same extent as in monolingual controls (C. Soares & F. Grosjean, 1981, Perception and Psychophysics, 29, 599-604; C. Soares, 1982, Neuropsychologia, 20, 653-659). The present study tested the same group of Portuguese-English bilinguals and a group of English-speaking monolinguals on a series of concurrent activity, or time-sharing, tasks. Greater levels of disruption in finger tapping with the right hand than with the left hand occurred during the performance of those tasks which required overt speech production, and this for both bilinguals and monolinguals. As in the previous studies, there were no lateralization differences across the bilinguals' two languages or between bilinguals and monolinguals. Thus, further evidence for equal levels of left-hemisphere dominance for language in bilinguals and monolinguals was provided by the use of the concurrent activities paradigm.     

Laterality differences for word identification in bilinguals

Twenty-three Spanish-English bilinguals were tachistoscopically presented with four-letter common nouns. They viewed 20 word pairs, first in their native language, then in the other, for 40 msec under simultaneous bilateral exposure. This paradigm has previously shown a strong right visual field and therefore left hemisphere superiority for words in a single language. The results show a word identification advantage in the right visual field. This indicates a left hemisphere advantage for processing of both languages, regardless of which was learned first. There are nevertheless wide individual differences in the number of bilinguals showing the expected asymmetry, as compared with monolinguals. There may be a trend, therefore, for less unilaterality of language function in bilinguals, although both languages are seen as being equally lateralized.     

Cerebral lateralization in bilinguals: Methodological issues

The literature on lateralization for language in bilinguals manifests two apparent contradictions. Some papers demonstrate differences in lateralization between bilinguals and monolinguals; others demonstrate none. In studies with exclusively bilingual subjects, some papers demonstrate differences between the lateralization for the two languages, while others demonstrate none. This paper discusses the range of methodological parameters which must be borne in mind when conducting or evaluating studies of lateralization for language in bilinguals. These include issues of subject selection, language and stimulus selection, testing procedures, data analysis, and interpretation of results.     

Learning across languages: bilingual experience supports dual language statistical word segmentation

Bilingual acquisition presents learning challenges beyond those found in monolingual environments, including the need to segment speech in two languages. Infants may use statistical cues, such as syllable‐level transitional probabilities, to segment words from fluent speech. In the present study we assessed monolingual and bilingual 14‐month‐olds’ abilities to segment two artificial languages using transitional probability cues. In Experiment 1, monolingual infants successfully segmented the speech streams when the languages were presented individually. However, monolinguals did not segment the same language stimuli when they were presented together in interleaved segments, mimicking the language switches inherent to bilingual speech. To assess the effect of real‐world bilingual experience on dual language speech segmentation, Experiment 2 tested infants with regular exposure to two languages using the same interleaved language stimuli as Experiment 1. The bilingual infants in Experiment 2 successfully segmented the languages, indicating that early exposure to two languages supports infants’ abilities to segment dual language speech using transitional probability cues. These findings support the notion that early bilingual exposure prepares infants to navigate challenging aspects of dual language environments as they begin to acquire two languages.     

Bilingualism affects picture naming but not picture classification

Bilinguals named pictures in their dominant language more slowly (and with more errors) than did monolinguals. In contrast, bilinguals named the same pictures as quickly as did monolinguals on the fifth presentation (in Experiment 2) and classified them (as human made or natural) as quickly and accurately as did monolinguals (in Experiment 1). In addition, bilinguals retrieved English picture names more quickly if they knew the name in both Spanish and English (on the basis of a translation test that bilinguals completed after the timed tasks), and monolingual response times for the same materials suggested that this finding was not obtained simply because names that were easier to translate were easier in general. These findings suggest that bilinguals differ from monolinguals at a postconceptual processing level, that implicit activation of lexical representations in the nontarget language can facilitate retrieval in the target language, and that being bilingual is analogous to having a lexicon full of lower frequency words, relative to monolinguals.     

Language and Cognitive Predictors of Lexical Selection in Storytelling for Monolingual and Sequential Bilingual Children

The primary purpose of the present study was to test language and cognitive predictors of lexical selection in the storytelling of monolingual and bilingual children. Measures of language proficiency and cognitive ability were assessed with both English- and Mandarin-speaking monolinguals and Mandarin-English bilinguals aged 4 to 6 years old. To elicit stories, children watched a cartoon and told the story back. Bilinguals did these tasks in both of their languages. The results showed that the bilinguals told stories with as many different words as monolinguals of both languages but scored lower on measures of vocabulary. For monolinguals, vocabulary score was an important predictor of lexical variety even after controlling for age. For bilinguals, attentional control was a significant predictor of lexical variety in their second language, English. These results suggest that for monolingual children, vocabulary size is an important predictor of lexical variety in stories, while bilingual children might rely more on cognitive abilities to lexicalize concepts.     

Brain bases of morphological processing in Chinese‐English bilingual children

Can bilingual exposure impact children's neural circuitry for learning to read? To answer this question, we investigated the brain bases of morphological awareness, one of the key spoken language abilities for learning to read in English and Chinese. Bilingual Chinese‐English and monolingual English children (N = 22, ages 7–12) completed morphological tasks that best characterize each of their languages: compound morphology in Chinese (e.g. basket + ball = basketball) and derivational morphology in English (e.g. re + do = redo). In contrast to monolinguals, bilinguals showed greater activation in the left middle temporal region, suggesting that bilingual exposure to Chinese impacts the functionality of brain regions supporting semantic abilities. Similar to monolinguals, bilinguals showed greater activation in the left inferior frontal region [BA 45] in English than Chinese, suggesting that young bilinguals form language‐specific neural representations. The findings offer new insights to inform bilingual and cross‐linguistic models of language and literacy acquisition.     

Language proficiency and executive control in proactive interference: evidence from monolingual and bilingual children and adults

Two studies are reported in which monolingual and bilingual children (Study 1) and adults (Study 2) completed a memory task involving proactive interference. In both cases, the bilinguals attained lower scores on a vocabulary test than monolinguals but performed the same on the proactive interference task. For the children, bilinguals made fewer intrusions from previous lists even though they recalled the same number of words. For the adults, bilinguals recalled more words than monolinguals when the scores were corrected for differences in vocabulary. In addition, there was a strong effect of vocabulary in which higher vocabulary participants recalled more words irrespective of language group. These results point to the important role of vocabulary in verbal performance and memory. They also suggest that bilinguals may compensate for weaker language proficiency with their greater executive control to achieve the same or better levels of performance as monolinguals.     

第二语言水平对双语者语言抑制能力的影响——来自英语–汉语单通道双语者和英语–美国手语双通道双语者的证据

采用同形异义词干扰任务考察第二语言水平对英语–汉语单通道双语者和英语–美国手语双通道双语者语言抑制能力的影响。结果发现:(1)高水平英语–汉语单通道双语者的语言抑制能力较强,但低水平英语–汉语单通道双语者与英语单语者的语言抑制能力没有显著差异,说明少量的双语经验不足以导致双语认知优势;(2)不同水平的英语–美国手语双通道双语者的语言抑制能力差异不显著。所以如此,与英语–美国手语双通道双语者不存在口语和手语的双语表征加工竞争有关。整个研究表明,双语认知优势效应与双语者的二语水平以及通道经验有关。     

Bilingual toddlers’ comprehension of mixed sentences is asymmetrical across their two languages

In bilingual language environments, infants and toddlers listen to two separate languages during the same key years that monolingual children listen to just one and bilinguals rarely learn each of their two languages at the same rate. Learning to understand language requires them to cope with challenges not found in monolingual input, notably the use of two languages within the same utterance (e.g., Do you like the perro? or ¿Te gusta el doggy?). For bilinguals of all ages, switching between two languages can reduce the efficiency in real‐time language processing. But language switching is a dynamic phenomenon in bilingual environments, presenting the young learner with many junctures where comprehension can be derailed or even supported. In this study, we tested 20 Spanish–English bilingual toddlers (18‐ to 30‐months) who varied substantially in language dominance. Toddlers’ eye movements were monitored as they looked at familiar objects and listened to single‐language and mixed‐language sentences in both of their languages. We found asymmetrical switch costs when toddlers were tested in their dominant versus non‐dominant language, and critically, they benefited from hearing nouns produced in their dominant language, independent of switching. While bilingualism does present unique challenges, our results suggest a united picture of early monolingual and bilingual learning. Just like monolinguals, experience shapes bilingual toddlers’ word knowledge, and with more robust representations, toddlers are better able to recognize words in diverse sentences.     

Speaking two languages with different number naming systems: What implications for magnitude judgments in bilinguals at different stages of language acquisition?

Differences between languages in terms of number naming systems may lead to performance differences in number processing. The current study focused on differences concerning the order of decades and units in two-digit number words (i.e., unit-decade order in German but decade-unit order in French) and how they affect number magnitude judgments. Participants performed basic numerical tasks, namely two-digit number magnitude judgments, and we used the compatibility effect (Nuerk et al. in Cognition 82(1):B25–B33, 2001) as a hallmark of language influence on numbers. In the first part we aimed to understand the influence of language on compatibility effects in adults coming from German or French monolingual and German–French bilingual groups (Experiment 1). The second part examined how this language influence develops at different stages of language acquisition in individuals with increasing bilingual proficiency (Experiment 2). Language systematically influenced magnitude judgments such that: (a) The spoken language(s) modulated magnitude judgments presented as Arabic digits, and (b) bilinguals’ progressive language mastery impacted magnitude judgments presented as number words. Taken together, the current results suggest that the order of decades and units in verbal numbers may qualitatively influence magnitude judgments in bilinguals and monolinguals, providing new insights into how number processing can be influenced by language(s).     

Language lateralization in bilinguals: enough already!

All clinical evidence points to the fact that both languages of bilinguals are subserved by the left hemisphere in the same proportion as in unilinguals. Half of the experimental studies have reported no significant difference in lateralization between unilinguals and bilinguals. Those studies that have reported a difference contradict each other with respect to the bilingual subpopulations that are alleged to exhibit differential laterality. In the face of the lack of demonstrated validity of dichotic, tachistoscopic, and time-sharing paradigms in reflecting laterality of language functions in bilinguals, it may be time for neuropsychologists to move on to more productive research.     

Not just semantics: Strong frequency and weak cognate effects on semantic association in bilinguals

To investigate the possibility that knowledge of two languages influences the nature of semantic representations, bilinguals and monolinguals were compared in a word association task. In Experiment 1, bilinguals produced less typical responses relative to monolinguals when given cues with a very common associate (e.g., given bride, bilinguals said “dress” instead of “groom”). In Experiment 2, bilinguals produced responses as typical as those of monolinguals when given cues with high-frequency associates, but not when given cues with lowfrequency associates. Bilinguals’ responses were also affected, to a certain extent, by the cognate status of the stimulus word pairs: They were more similar to monolinguals’ responses when the cue and its strongest associate were both cognates (e.g., minute-second is minuto-segundo in Spanish), as opposed to both being noncognates. Experiment 3 confirmed the presence of a robust frequency effect on bilingual but not on monolingual association responses. These findings imply a lexical locus for the bilingual effect on association responses and reveal the association task to be not quite as purely semantic as was previously assumed.     

The bilingual L2 advantage in recognition memory

To better understand the mechanisms by which bilingual proficiency impacts memory processes, two recognition memory experiments were conducted with matched monolingual and bilingual samples. In Experiment 1, monolingual speakers of English and Spanish studied high- and low-frequency words under full attention or cognitive load conditions. In Experiment 2, Spanish–English bilingual participants studied high- and low-frequency words under full-attention conditions in each language. For both monolinguals and bilinguals, low-frequency words were better recognized than high-frequency words. The central new findings were that bilingual recognition was more accurate in the less fluent language (L2) than in the more fluent language (L1) and that bilingual L2 recognition was more accurate than monolingual recognition. The bilingual L2 advantage parallels word frequency effects in recognition and is attributed to the greater episodic distinctiveness of L2 words, relative to L1 words.     

Neurolinguists, beware! The bilingual is not two monolinguals in one person

Two views of bilingualism are presented--the monolingual or fractional view which holds that the bilingual is (or should be) two monolinguals in one person, and the bilingual or wholistic view which states that the coexistence of two languages in the bilingual has produced a unique and specific speaker-hearer. These views affect how we compare monolinguals and bilinguals, study language learning and language forgetting, and examine the speech modes--monolingual and bilingual--that characterize the bilingual's everyday interactions. The implications of the wholistic view on the neurolinguistics of bilingualism, and in particular bilingual aphasia, are discussed.     

Bilinguals in a monolingual and a bilingual speech mode: The effect on lexical access

The time course of lexical access in fluent Portuguese-English bilinguals and in English speaking monolinguals was examined during the on-line processing of spoken sentences using the phoneme-triggered lexical decision task (Blank, 1980). The bilinguals were tested in two distinct speech modes: a monolingual, English or Portuguese, speech mode, and a bilingual, code-switching, speech mode. Although the bilingual’s lexical decision response times to word targets in the monolingual speech modes were identical to those of the monolingual subjects, their response times to code-switched word targets in the bilingual mode were significantly slower. In addition, the bilinguals took longer to detect nonwords in both the monolingual and bilingual modes. These results confirm that bilinguals cannot totally deactivate their other language when in a monolingual speech mode. It is hypothesized that bilinguals search both lexicons when confronted with nonwords, even when in a totally monolingual mode, and that they search the base-language lexicon before the other lexicon when in a bilingual, code-switching, speech mode.     

Cross-language activation in children's speech production: evidence from second language learners, bilinguals, and trilinguals

In five experiments, we examined cross-language activation during speech production in various groups of bilinguals and trilinguals who differed in nonnative language proficiency, language learning background, and age. In Experiments 1, 2, 3, and 5, German 5- to 8-year-old second language learners of English, German-English bilinguals, German-English-Language X trilinguals, and adult German-English bilinguals, respectively, named pictures in German and in English; in Experiment 4, 6- to 8-year-old German monolinguals named pictures in German. In both language conditions, cognate status was manipulated. We found that the bidirectional cognate facilitation effect was significant in all groups except the German monolinguals (Experiment 4) and, critically, the child second language learners (Experiment 1) in whom only native language (L1) German had an effect on second language (L2) English. The findings demonstrate how the integration of languages into a child's system follows a developmental path that, at lower levels of proficiency, allows only limited cross-language activation. The results are interpreted against the backdrop of the developing language systems of the children both for early second language learners and for early bi- and trilinguals.     

Bilinguals Show Weaker Lexical Access During Spoken Sentence Comprehension

When bilinguals process written language, they show delays in accessing lexical items relative to monolinguals. The present study investigated whether this effect extended to spoken language comprehension, examining the processing of sentences with either low or high semantic constraint in both first and second languages. English-German bilinguals, German-English bilinguals and English monolinguals listened for target words in spoken English sentences while their eye-movements were recorded. Bilinguals’ eye-movements reflected weaker lexical access relative to monolinguals; furthermore, the effect of semantic constraint differed across first versus second language processing. Specifically, English-native bilinguals showed fewer overall looks to target items, regardless of sentence constraint; German-native bilinguals activated target items more slowly and maintained target activation over a longer period of time in the low-constraint condition compared with monolinguals. No eye movements to cross-linguistic competitors were observed, suggesting that these lexical access disadvantages were present during bilingual spoken sentence comprehension even in the absence of overt interlingual competition.     

Language learning and control in monolinguals and bilinguals

Parallel language activation in bilinguals leads to competition between languages. Experience managing this interference may aid novel language learning by improving the ability to suppress competition from known languages. To investigate the effect of bilingualism on the ability to control native-language interference, monolinguals and bilinguals were taught an artificial language designed to elicit between-language competition. Partial activation of interlingual competitors was assessed with eye-tracking and mouse-tracking during a word recognition task in the novel language. Eye-tracking results showed that monolinguals looked at competitors more than bilinguals, and for a longer duration of time. Mouse-tracking results showed that monolinguals' mouse movements were attracted to native-language competitors, whereas bilinguals overcame competitor interference by increasing the activation of target items. Results suggest that bilinguals manage cross-linguistic interference more effectively than monolinguals. We conclude that language interference can affect lexical retrieval, but bilingualism may reduce this interference by facilitating access to a newly learned language.     

Effects of Bilingual Language Use and Language Proficiency on 24-month-olds’ Cognitive Control

ABSTRACT

Although a bilingual advantage has been reported for various measures of cognitive control, most previous studies have looked at a limited range of cognitive control measures. Furthermore, they typically leave unaddressed whether positive effects of bilingualism hold for all bilinguals or whether these are modulated by differences in bilingual language use and proficiency of children and their parents. This study reports on tasks of selective attention and inhibitory control from 24-month-old bilinguals (n = 37) and monolinguals (n = 58). Their parents completed a Dutch vocabulary checklist assessing receptive and productive vocabulary as well as questionnaires on children’s attentional focusing, attention shifting and inhibitory control, and language background. Linear mixed-effect regressions showed no differences on cognitive control between the monolinguals and bilingual groups. However, analyses taking into account differences in children’s bilingual language use and proficiency and of their parents revealed a more nuanced picture. Specifically, children’s degree of balanced language usage predicted parent-rated cognitive control. Furthermore, bilingual toddlers who had parents were low proficient in one of the home languages showed significantly better performance on a selective attention task than toddlers whose parents were both proficient in both home languages. These findings suggest that both children’s active usage of two languages and their experience with switching depending on their interlocutor are related to cognitive control performance in young bilingual children. As such, they add to a growing body of evidence that the bilingual advantage in cognitive control is tied to specific conditions of bilingualism, already at a young age.