In America, there is a large English- Spanish bilingual community, especially in the bordering states. There is often debate on whether being bilingual is actually beneficial for individuals’ intellectual capabilities or even enhance them. The exposure to an additional language at an early age is widely assumed enhance the language and auditory abilities of the child.
In the investigation by Kraus et al (2012), they investigated 48 incoming freshmen, 28 of whom were bilingual in Spanish and English and 20 monolinguals. The aim of the investigation was to test whether bilingual teens, whose brains were still developing, would also show an enhanced response to complex sounds when compared to monolingual teens. With the use of electrodes in order to record the intensity of the participants’ auditory brainstem response, the researchers played the syllable “da”. The results indicated that the bilinguals display a large response. When the next control of background noise was played for the participants, the monolinguals displayed a weaker response than when it was played alone. The bilingual participants displayed identical responses with and without the background noise. In a second experiment conducted by the researchers, the participants were given a selective attention test in which they were asked to click a mouse when only a 1 was either seen or heard. A total of 500 trials were conducted of either one or two seconds each over a period of 20 period. The results from the experiments showed that the bilinguals had outperformed the monolinguals on this test. The bilinguals displayed stronger behavioral measure of attention control and enhanced subcortical representation to the responses to the syllable [da] compared to monolinguals. The results suggest that bilingualism may help improve skills in selective attention through the enhancement of auditory brainstem response. Due to the subcortical and cortical responses being simultaneously record, there is a possibility that the established relationship may partly reflect a byproduct of the procedure of the recording.
The area of the brain that is vital for language ability is the left inferior frontal gyrus, which is crucial for language production and comprehension because the majority of language processing takes place within the left hemisphere.
Through a study conducted by Kovelman et al (2008), bilinguals and monolinguals were compared on how they activate language brain areas in response to a language task. The researchers also addressed the question of whether there was a “neural signature” of bilingualism. The experiment consisted of healthy adults who were highly proficient and early-exposed in both Spanish-English, and English monolinguals. The participants were scanned by functional magnetic resonance imagining (fMRI) while completing a syntactic sentence judgment task. The task exploited the linguistic properties of differences between English and Spanish. This allows the exploration of bilingual differences and similarities in neural and behavioral responses compared to monolinguals, as well as between the two languages of the bilinguals. The results of the study showed that in English, both bilinguals and monolinguals had the same speed and accuracy in behavior, however the bilinguals had a different performance pattern in Spanish. The fMRI analysis revealed that both the monolinguals and bilinguals showed increased activity in the left inferior frontal cortex. A vital differences displayed was that while processing English, the bilinguals had a significantly greater increase in the blood oxygenation level-dependent signal in the left inferior frontal cortex in comparison to the English monolinguals. This result suggests that there may be a possible neural signature of bilingualism.
How Bilingualism Affects Brain structure
The ability of speaking two languages is widely known to be advantageous for multiple opportunities and be used to measure cognitive intelligence, however bilinguals show that there is no difficulty in doing so. There are few different times of when people become bilingual; learning a second language from birth, during early childhood, late childhood, adolescence, and adulthood. Those who learn a second language in the later year is often a result of being in an immersive environment. The effects on the brain from learning a second language due to being in an immersive environment or to bilingual exposure has yet to be concluded, however, studies with the use of a voxel-based morphometry, a neuroimaging analysis technique which investigates the central differences in the anatomy of the brain, doing so with the approach of statistical mapping.
An objection to the VBM includes that it is extremely sensitive. A simple movement by a subject during the screening may affect results. The VBM is also extremely sensitive to various artifacts such as the misalignment of the structure of the brain and the misclassification of brain tissue.
Being bilingual has been considered an advantage compared to being monolingual. In a study conducted by Andrea Mechelli et al (2004), voxel-based morphometry (VBM) was used to investigate the structural plastically in healthy right-handed English and Italian bilinguals. The participants of this experiment included 25 monolinguals who had little or no exposure to a second language; 25 early bilinguals, who had learned a second European language before the age of 5 and practiced regularly since, 33 late bilinguals who had learned a second European languages between the ages of 10 and 15 years and regularly practice for the duration of at least 5 years. Each participant was a native English speaker and shared similar age and education levels. The voxel-based morphometry revealed that there was a greater grey-matter density in the inferior parietal cortex in bilinguals compared to the monolinguals.
Due to the sensitivity of the VBM, the measured results may have flaw or mismapping.
With the use of a magnetic resonance imaging (MRI), Klein et al (2013) investigated the effects of bilingualism on brain structure by examining 22 monolinguals’ and 66 bilinguals’ cortical thickness. Some of the bilinguals had learned both languages simultaneously (0-3 years) meanwhiles ome had learned their second language after being proficient in their first language during that early to late childhood. The results of the MRI displayed that the subjects with a second language had a significantly thicker cortex in the left inferior frontal gyrus (IFG) and thinner cortex in the right IFG. There were significant correlations between the age of learning the second language and cortical thickness in bilinguals; age acquisition correlated with cortical thickness positively in the left IFG and appeared negatively in the right IFG. The monolinguals and bilinguals who learned the second language simultaneously did not display any difference in cortical thickness at all. These results reveal that there is age-dependent modification in the brain structure when learning a second language, and the simultaneous learning of two language has no extra effect on brain development.
Brain structure and cognitive effects in Mandarin- English bilinguals.
Many studies involving the cognitive research of bilinguals only investigate English and Latin based languages. The cognitive effect of bilingualism for English and Sino-Tibetan languages has also recently been investigated. A method of investigating the effect, brain scanners such as Magnetoencephalography and Functional Magnetic Resonance Imaging were used. Wang et al (2011) conducted a study investigating if Mandarin – English bilingual speaker have the same cortical areas or develop distant language-specific networks without word processing overlaps with the use of magnetoencephalography (MEG). Eight Mandarin-English adult bilinguals and eight English speaking monolinguals participants were chosen for this study. They were all scanned by the MEG while being audio-visually presented with single-word paradigms. The results of the experiment showed that there was a beta-band power suppression in the right inferior parietal lobe covering the supramarginal gyrus and angular gyrus for bilinguals when processing Mandarin compared to processing English. Despite the Mandarin-English bilinguals and monolinguals’ neural system for word processing was highly similar, the bilinguals had strong right hemisphere involvement. As the right hemisphere has the ability to generate verbal inflections and detecting tones of voice, it’s discovered involvement through the MEG provides better insight in the understanding of the language system in bilinguals’ and monolinguals’ brain.
Chee et al (1999) examined 24 right-handed Mandarin- English fluent bilinguals; 15 whom were exposed to both languages before the age of 6; nine exposed to Mandarin early in their childhood while being exposed to English after 12 years old. fMRI scans were used on the participants while the they performed cued word generation in each language. It was found that in both languages, the prefrontal, parietal, and temporal regions were active, as was the supplementary motor area. There was no significant difference in any of the participants regarding the activation that were peak-location or hemispheric in the pre frontal language areas. Bilinguals who learned the second language early or late in their childhood displayed similar patterns of overlapping activity. The findings show that common cortical areas are active when Mandarin- English bilinguals perform cued word generation.