Linguistic and non-linguistic factors influencing attentional control performance in bilinguals and monolinguals in Singapore and Edinburgh

The suggestion that bilinguals show enhanced cognitive control compared to monolinguals in certain aspects of executive function has received much contention. While this has been explained as a result of the extensive training in bilinguals having to manage the conflict that arises from their concurrently active langauges, others have argued that the superiority in executive control is attenuated when background variables such as immigration status, education and general cognitive ability is taken into account. This thesis was motivated by the general question: How is executive control influenced by differing bilingualism experiences? To this end, we compared attentional control performance in bilinguals and monolinguals on the Attention Network Test, the auditory Elevator task (Test of Everyday Attention), and the number Stroop task. The main aim of the thesis was to examine the role of two bilingualism factors: (i) interactional context (defined in the Adaptive Control Hypothesis, Green & Abutalebi, 2013), which pertains to how bilinguals switch between their languages, and (ii) linguistic distance, which refers to the extent of similarity between the bilingual’s languages. The comparison between Edinburgh monolinguals, Edinburgh late bilinguals, Edinburgh early bilinguals, and Singapore early bilinguals as differentiated by their interactional context revealed better performance in bilinguals on two specific test components. Singapore bilinguals, who came from a dual-language and dense code-switching context, showed enhanced conflict resolution on the Attention Network Test, whilst Edinburgh late bilinguals, who were from a single-language context, were better on the Elevator reversal subtest tapping on attentional switching. The results thus suggest differential effects of interactional context on attentional control. We further compared task performance of bilinguals with related or distant L1-L2 combinations as defined by the linguistic and orthography overlap between their two languages. The data did not support a role of linguistic distance on attentional control. Edinburgh bilinguals studying an Indo-European language performed similarly to those studying the non Indo-European languages of Chinese and Japanese. In Singapore bilinguals, English-Chinese bilinguals also did not differ from English-Malay bilinguals on any of the test components. We supplemented the investigation by further examining if the factors of test-order and age could impact on how differences between monolinguals and bilinguals are exhibited. Our results suggest that monolinguals may show an improvement in attentional control after relatively short periods of engagement in experimental tasks, whilst bilinguals did not receive this boost. Test order may therefore partly explain the inconsistencies in literature regarding the claimed bilingual advantage. The comparison between older and younger adults also implied an effect of age. In young adults, bilinguals outperformed monolinguals on the Elevator reversal subtest of auditory switching, whereas the advantage shown in older bilinguals was on visual attentional orienting. The results across the various themes are reviewed and discussed with relevance to the current standing in the field, and suggestions for future research directions are put forth