Effects of language learning and bilingualism on executive functions: influence of exposure, experience and linguistic distance
Item statusRestricted Access
Embargo end date31/07/2022
The debate as to whether bilingual experience benefits individuals in terms of certain aspects of executive function has received much attention. The differences on cognitive performance between monolinguals and bilinguals have not been consistently replicated, which has raised concerns regarding the reliability and robustness of the cognitive effects associated with bilingualism. Given that bilingualism is a multidimensional, continuous, and dynamic phenomenon and varies with respect to many factors, the specific bilingual experience plays an important role in modulating the degree of bilingualism and, in turn, affects executive functions. Hence, identifying individuals’ language experience is crucial for understanding the language control in bilinguals; importantly, it can shed light on the issue of the inconsistent evidence and identifying the possible reasons behind it. The first aim of this thesis is to understand the effects of specific language experience on executive functions (EF), particularly the components involved in language control, such as inhibitory control. The second aim is to explore the unsolved and lesser-investigated issues in the field of bilingualism research and to examine their impact on executive control in the context of bilingualism. These issues include: (i) inhibitory mechanisms for the reported inhibitory benefits associated with bilingualism (ii) pathways of language acquisition (i.e., language immersion versus instruction); and (iii) cognitive consequences of linguistic differences, such as linguistic distance and language script. EF performance in all of the studies carried out in this thesis was assessed by at least four non-linguistic cognitive tasks; namely, the Attention Network Task (ANT), the Number Stroop task, the Elevator subtests of the Test of Everyday Attention (TEA), and the Corsi Tapping Task (CTT), tapping into multiple dimensions of EF. The selection of the experimental tasks was based on the fact that the nature of language learning entails multiple domains, such as the visual (e.g., reading and writing), auditory (e.g., listening and speaking), and working memory (e.g., lexical and grammatical acquisition) domains. An additional arrow version of Simon task was included in the second and fourth studies. The first study investigates how language experience modulates EF in early adulthood Chinese learners of English. The results show that different aspects of language experience affect specific subcomponents of EF: language proficiency affects switching ability, disengagement of attention, inhibition in the visual domain, and auditory attentional switching, language exposure mainly affects switching ability and disengagement of attention, whereas the length of language use affects inhibition in both the visual and auditory domains. The second study examines the inhibitory mechanisms in young adult monolinguals and bilinguals and the role of language proficiency in modulating EF. The results show that bilingualism mainly influences interference suppression, but not response inhibition. Language proficiency turns out to differentially affect specific aspects of executive control and influence the emergence of group differences between monolinguals and bilinguals. The third study explores potentially different cognitive consequences of two pathways of language acquisition; namely, language instruction and language immersion. We examined EF longitudinally in young adult Chinese speakers learning English through instruction and immersion, respectively. The results suggest that overall the cognitive effects of L2 exposure are comparable in an instruction and immersion setting. However, subtle differences can be detected on specific cognitive tests such as auditory inhibition. The fourth study investigates whether linguistic differences extend to the cognitive domain as a result of language learning in Chinese and European populations. Specifically, the role of linguistic distance in spoken languages in modulating language control and executive control (Experiment 1), and how language script in written languages affects language acquisition and cognitive performance (Experiment 2). The results suggest that a larger linguistic distance is associated with better cognitive control; namely, general-domain executive control and inhibitory control. Moreover, language script plays a modulating role in cognitive performance: native Chinese speakers showed superior performance in visual attention tasks and mental rotation, while native English speakers obtained better performance in the auditory attention tasks. The results demonstrate that native language, linguistic distance, and script are significant predictors to EF, although the interaction with other factors, such as cultural differences and education systems, remains to be further studied. Taken together, this thesis focuses on the different aspects of language learning and bilingualism on different sub-components of executive functions in young adult populations. As to specific bilingual experience, we have investigated the less-explored factors, such as pathways of language acquisition (instruction vs. immersion), linguistic distance, and language scripts, and their impact on cognitive performance. Moreover, we have examined the effects of bilingualism on different types of inhibition mechanism (interference suppression vs. response inhibition) to specify the relationship between language control and inhibitory control. These findings contribute to our understanding of the key aspects of the bilingual experience that are responsible for the emergence of the cognitive effects of young adulthood bilingualism.