Left hemisphere language lateralization in bilinguals and monolinguals

Tachistoscopic studies of lateralization in bilinguals suggest that there is a greater degree of right hemisphere involvement in their processing of language than is typically found in monolinguals. However, most of the studies reviewed failed to control the sex, handedness, and degree of fluency of the subjects and did not include a monolingual comparison group. The present study used adult right-handed males (Portuguese-English bilinguals and English-speaking monolinguals) in a tachistoscopic word-reading task. In Experiment 1, the words from the bilinguals’ two languages were presented in mixed blocks, while in Experiment 2, they were presented in separate blocks. The results were: (1) a similar level of left hemisphere advantage for language in the bilingual and the monolingual groups, (2) no evidence of greater heterogeneity of asymmetry patterns in bilinguals, and (3) a significant correlation (r=.61) for lateralization levels of the bilinguals’ two languages. These results indicate that language is processed primarily in the left hemisphere of both bilinguals and monolinguals.     

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.     

Bilingual speech: Bilateral control?

Forty bilinguals from several language backgrounds were contrasted to a group of English-speaking monolinguals on a verbal-manual interference paradigm. For the monolinguals, concurrent finger-tapping rate during speech output tasks was disrupted only for the right hand, indicating left-hemisphere language dominance. Bilingual laterality patterns were a function of language used: native (L1) versus second acquired (L2), and age of L2 acquisition. Early bilinguals (L1 + L2 acquisition prior to age 6) revealed left-hemisphere dominance for both languages, whereas late bilinguals (L2 acquired beyond age 6) revealed left-hemisphere dominance only for L1 and symmetrical hemispheric involvement for L2.     

The bilingual effects of linguistic distances on episodic memory and verbal fluency

The impact of linguistic distance or the relatedness between two languages, on bilinguals’ episodic memory performance and verbal fluency is an understudied area. Thus, the purpose of this study was to determine if differences in linguistic distances have differential effects on these abilities. Measures of episodic recognition, categorical fluency, and global cognitive functioning were also considered in the analyses. Two matched samples with participants living and educated in Sweden were drawn from the Betula Prospective Cohort Study. Results showed that bilinguals who speak linguistically similar languages (Swedish and English), performed significantly better than monolinguals on both episodic memory recall and letter fluency, while bilinguals who speak two languages that are more distant (Swedish and Finnish), showed no advantages compared to their monolingual counterparts. For both tasks, however, a linear trend was observed indicative of better performance for the Swedish-English group compared to the Finnish-Swedish group, and for the Swedish-Finnish group compared to the monolinguals group. As expected, no differences between groups were found in any of the other cognitive tasks. Overall, results suggest that the impact of linguistic distances should be explored in more detail in the future.     

Do French–English Bilingual Children Gesture More Than Monolingual Children?

Previous studies have shown that bilingual adults use more gestures than English monolinguals. Because no study has compared the gestures of bilinguals and monolinguals in both languages, the high gesture rate could be due to transfer from a high gesture language or could result from the use of gesture to aid in linguistic access. In this study we tried to distinguish between those causes by comparing the gesture rate of 10 French–English bilingual preschoolers with both 10 French and 10 English monolinguals. All were between 4 and 6 years of age. The children were asked to watch a cartoon and tell the story back. The results showed the bilingual children gestured more than either group of monolinguals and at the same rate in both French and English. These results suggest that that the bilinguals were not gesturing because they were transferring the high gesture rate from one language to another. We argue that bilinguals might gesture more than monolinguals to help formulate their spoken message.     

双语和双言对图片命名和分类的不对称影响

采用普通话-英语双语者、粤语-普通话双言者和普通话单言者为被试, 比较他们图片命名与图片分类的成绩。结果表明, 普通话-英语双语者用优势语言命名图片的反应时比普通话单语者显著长, 错误率显著高。在第4次和第5次重复呈现图片时, 普通话-英语双语者与普通话单语者的命名反应差异不显著。普通话-英语双语者与普通话单语者对图片分类的反应差异不显著。这表明, 双语影响图片命名却不影响图片分类。粤语-普通话双言者对图片命名和图片分类的反应模式和普通话-英语双语者一致, 表明粤语-普通话双言和普通话-英语双语有类似的认知机制。普通话和粤语是作为两种语言储存在粤语-普通话双言者的头脑中的。     

A time sharing cross-sectional study of monolinguals and bilinguals at different levels of second language acquisition

Several methodological factors associated with the concurrent activities (finger-tapping) paradigm were considered in a cross-sectional study investigating cerebral patterns of asymmetry in three groups of English-speaking non-Hispanic dextral males at three levels of second language (Spanish) acquisition and one control group of monolinguals. Results revealed the fluent bilinguals to be bilateral and significantly different from other groups for native language tasks in English. Moreover, a priori contrasts indicate that greater right- than left-hand disruption in concurrent tapping may be typical of monolinguals, but can be influenced by other factors. Monolingual reliability test-retest correlations were .77 and .47.     

Dual language use in sign-speech bimodal bilinguals: fNIRS brain-imaging evidence

The brain basis of bilinguals’ ability to use two languages at the same time has been a hotly debated topic. On the one hand, behavioral research has suggested that bilingual dual language use involves complex and highly principled linguistic processes. On the other hand, brain-imaging research has revealed that bilingual language switching involves neural activations in brain areas dedicated to general executive functions not specific to language processing, such as general task maintenance. Here we address the involvement of language-specific versus cognitive-general brain mechanisms for bilingual language processing. We study a unique population, bimodal bilinguals proficient in signed and spoken languages, and we use an innovative brain-imaging technology, functional Near-Infrared Spectroscopy (fNIRS; Hitachi ETG-4000). Like fMRI, the fNIRS technology measures hemodynamic change, but it is also advanced in permitting movement for unconstrained speech and sign production. Participant groups included (i) hearing ASL–English bilinguals, (ii) ASL monolinguals, and (iii) English monolinguals. Imaging tasks included picture naming in “Monolingual mode” (using one language at a time) and in “Bilingual mode” (using both languages either simultaneously or in rapid alternation). Behavioral results revealed that accuracy was similar among groups and conditions. By contrast, neuroimaging results revealed that bilinguals in Bilingual mode showed greater signal intensity within posterior temporal regions (“Wernicke’s area”) than in Monolingual mode. Significance: Bilinguals’ ability to use two languages effortlessly and without confusion involves the use of language-specific posterior temporal brain regions. This research with both fNIRS and bimodal bilinguals sheds new light on the extent and variability of brain tissue that underlies language processing, and addresses the tantalizing questions of how language modality, sign and speech, impact language representation in the 7brain.     

Bimodal bilinguals reveal the source of tip-of-the-tongue states

Bilinguals report more tip-of-the-tongue (TOT) failures than monolinguals. Three accounts of this disadvantage are that bilinguals experience between-language interference at (a) semantic and/or (b) phonological levels, or (c) that bilinguals use each language less frequently than monolinguals. Bilinguals who speak one language and sign another help decide between these alternatives because their languages lack phonological overlap. Twenty-two American Sign Language (ASL)-English bilinguals, 22 English monolinguals, and 11 Spanish-English bilinguals named 52 pictures in English. Despite no phonological overlap between languages, ASL-English bilinguals had more TOTs than monolinguals, and equivalent TOTs as Spanish-English bilinguals. These data eliminate phonological blocking as the exclusive source of bilingual disadvantages. A small advantage of ASL-English over Spanish-English bilinguals in correct retrievals is consistent with semantic interference and a minor role for phonological blocking. However, this account faces substantial challenges. We argue reduced frequency of use is the more comprehensive explanation of TOT rates in all bilinguals.     

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.     

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.     

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.     

Are bilingual advantages dependent upon specific tasks or specific bilingual experiences?

Paap and Greenberg concluded that there is no coherent evidence for bilingual advantages in executive processing. More optimistic researchers believe that the advantages may be restricted to certain types of bilinguals. Recent large-scale and lifespan investigations that tested highly fluent bilinguals from communities where the same two languages are spoken by most residents reported no bilingual advantages in any age group or in any of the tasks used to measure executive functioning. The present study takes a complementary approach by examining a sample that is quite homogeneous in terms of current life experiences, but heterogeneous in terms of its exposure to second languages. The composite database of 168 bilinguals and 216 monolinguals is used to explore for differences based on: (1) the age of acquiring a second language (L2), (2) the relative proficiency of an L2 and (3) the number of languages used. Across 12 different measures of executive function, derived from 4 different nonverbal tasks, there was no consistent evidence supporting the hypotheses that either early bilingualism, highly fluent balanced bilingualism, or trilingualism enhances inhibitory control, monitoring or switching. In fact, when statistically significant effects did occur, they more often disconfirmed than confirmed these hypotheses.     

Early bilingualism enhances mechanisms of false‐belief reasoning

In their first years, children's understanding of mental states seems to improve dramatically, but the mechanisms underlying these changes are still unclear. Such ‘theory of mind’ (ToM) abilities may arise during development, or have an innate basis, developmental changes reflecting limitations of other abilities involved in ToM tasks (e.g. inhibition). Special circumstances such as early bilingualism may enhance ToM development or other capacities required by ToM tasks. Here we compare 3‐year‐old bilinguals and monolinguals on a standard ToM task, a modified ToM task and a control task involving physical reasoning. The modified ToM task mimicked a language‐switch situation that bilinguals often encounter and that could influence their ToM abilities. If such experience contributes to an early consolidation of ToM in bilinguals, they should be selectively enhanced in the modified task. In contrast, if bilinguals have an advantage due to better executive inhibitory abilities involved in ToM tasks, they should outperform monolinguals on both ToM tasks, inhibitory demands being similar. Bilingual children showed an advantage on the two ToM tasks but not on the control task. The precocious success of bilinguals may be associated with their well‐developed control functions formed during monitoring and selecting languages.     

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.     

The Distinctiveness of Emotion Words: Does It Hold for Foreign Language Learners? The Case of Arab EFL Learners

Empirical evidence has recently been provided for the distinctiveness of emotion words as compared to abstract and concrete words for monolinguals, calling for a reconsideration of the relation between emotion and language. The present study investigates whether the distinctiveness of emotion words among monolinguals holds for foreign language learners. To this end, three groups (n?=?120 per group) of late Arabic-English bilinguals who learned English as a foreign language completed tasks including free recall, rating, and discrete word association. One group completed the tasks in Arabic while the other two groups, representing two levels of foreign language exposure, completed the tasks in English. Planned comparisons indicated the distinctiveness of emotion words in the participants’ first and foreign languages in the free recall and rating tasks while no significant differences were found in the word association task. The results are discussed in light of the existing literature and relevant theoretical models.     

Lateralization effects in the perception of Hebrew and English words

A series of four experiments was conducted on Israelis with a good knowledge of English, Anglo-Saxons with a good knowledge of Hebrew, and full Bilinguals of the two languages. In all experiments words were presented vertically and measurements of both accuracy and response times were taken. Experiments 1 and 2 examined the perception of Hebrew words in unilateral and bilateral conditions, respectively; Experiments 3 and 4 examined the perception of both Hebrew and English words in these two conditions. The results revealed right visual field advantage in the perception of words in both languages and in all groups. A reversal between the two conditions was not found. The data support the hypothesis whereby nonnative languages are less lateralized than native ones, but they indicate that full bilinguals are more, not less, lateralized than monolinguals. Various hypothesis regarding the relationship between lateralization and bilingualism are discussed.     

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.     

The perception of stop consonant voicing by Spanish-English bilinguals

The performance of Spanish-English bilinguals in two perception tasks, using a synthetic speech continuum varying in voice onset time, was compared with the performance of Spanish and English monolinguals. Voice onset time in speech production was also compared between these groups. Results in perception of bilinguals differed from that of both monolingual groups. Results of bilingual production in their two languages conformed with results obtained from each monolingual group. The perceptual results are interpreted in terms of differences in the use of available acoustic cues by bilingual and monolingual listeners of English and Spanish.     

Cognitive control and lexical access in younger and older bilinguals

Ninety-six participants, who were younger (20 years) or older (68 years) adults and either monolingual or bilingual, completed tasks assessing working memory, lexical retrieval, and executive control. Younger participants performed most of the tasks better than older participants, confirming the effect of aging on these processes. The effect of language group was different for each type of task: Monolinguals and bilinguals performed similarly on working memory tasks, monolinguals performed better on lexical retrieval tasks, and bilinguals performed better on executive control tasks, with some evidence for larger language group differences in older participants on the executive control tasks. These results replicate findings from individual studies obtained using only 1 type of task and different participants. The confirmation of this pattern in the same participants is discussed in terms of a suggested explanation of how the need to manage 2 language systems leads to these different outcomes for cognitive and linguistic functions.