Recent evidence suggests that the task of managing a bilingual individual’s two languages is carried out by general attentional mechanisms. Researchers have found evidence for bilingual advantages in attention, specifically on tasks that involve inhibiting irrelevant information, which are believed to stem from lifelong practice at inhibiting the language system not currently in use. In the present study we hypothesized that, since bilinguals are better at inhibiting irrelevant information, they should show memory disadvantages if previously irrelevant information becomes relevant. 12 bilingual and 12 monolingual participants (age range:19-27) were tested in an eye tracking paradigm where the relational manipulation effect (the tendency to direct more viewing to manipulated regions of previously viewed scenes) was used to access memory for scenes that had been presented as distractors during a study block. No differences in memory were observed. However, we observed a significant difference in general viewing patterns between the two language groups, such that bilinguals made significantly shorter fixations.

Recent evidence suggests that the task of managing a bilingual individual’s two languages is carried out by general attentional mechanisms. Researchers have found evidence for bilingual advantages in attention, specifically on tasks that involve inhibiting irrelevant information, which are believed to stem from lifelong practice at inhibiting the language system not currently in use. In the present study we hypothesized that, since bilinguals are better at inhibiting irrelevant information, they should show memory disadvantages if previously irrelevant information becomes relevant. 12 bilingual and 12 monolingual participants (age range:19-27) were tested in an eye tracking paradigm where the relational manipulation effect (the tendency to direct more viewing to manipulated regions of previously viewed scenes) was used to access memory for scenes that had been presented as distractors during a study block. No differences in memory were observed. However, we observed a significant difference in general viewing patterns between the two language groups, such that bilinguals made significantly shorter fixations.

The ease at which individuals acquire a second language is astounding. Individuals are capable of learning a second language at any point through out their lifespan, although it is easier to learn a second language early in life. With increasing knowledge about linguistic neural processing and the brain’s capacity for plasticity, the research on bilingualism has increased substantially. Researchers have become increasingly more interested in the long-term effects of acquiring a second language, especially the enhancement of executive function (EF). This enhancement, also known as bilingual advantage, has been studied for a range of EFs, including inhibition, attention, problem solving, and reasoning. Although this effect was first demonstrated in bilingual children, researchers have extended the quest for understanding to young, middle, and older adults; however, the research findings are mixed for young adults. In order clarify these mixed results, the age of second language acquisition has been included as an experimental variable, producing three relevant groups: early bilinguals, late bilinguals, and monolinguals. There are several ways in which EFs can be measured, including behavioral rating scales, computerized cognitive tasks with behavioral outcomes (i.e., response times and accuracy), and computerized event-related potential cognitive tasks. A novel multi-level approach to measuring the bilingual advantage was developed and used as a framework for the current dissertation; i.e., the bilingual advantage was measured at three levels of measurement. This approach predicts that more complex levels of measurement (i.e., executive behaviors) would produce null findings between the three groups, while differences between early bilinguals and the other two groups would be predicted for less complex levels of measurement (i.e., neurophysiological markers). This approach predicts mixed results for levels of measurement that involve moderate complexity (e.g., computerized tasks of EF). Early bilinguals, late bilinguals, and monolinguals were compared across three hierarchical levels of measurement: (i) executive behaviors; (ii) information processing (i.e., computerized tasks of EF); and (iii) neurophysiology (i.e., event-related potential paradigm). Findings generally support the multi-level approach: no differences were found at the executive behavior level, limited and mixed differences were found at the information processing level, and differences between groups were found at the neurophysiological level. / Graduate

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Yes / This study examined whether the proposed bilingual advantage in inhibitory control and working memory can be extended to a trilingual advantage, and assessed any age-related effects on a continuum in young adults to older adults. Trilinguals, bilinguals and monolinguals’ performance on the Simon task and a numerical version of the N-back task was compared. On the Simon task, there was no language group difference observed, although the data show an age-related decline in inhibitory control only in trilinguals, but not in bilinguals or monolinguals. No clear language group differences were observed between trilinguals and bilinguals on the N-back task, however an overall trilingual and bilingual disadvantage, compared to monolinguals, was observed. Together the results suggest that managing two or three languages, compared to just one, may have a negative impact on inhibitory control and working memory performance. Importantly, they highlight the need to control for a possible confounding effect of including trilinguals/multilinguals in bilingual cohorts and to ensure that participants in monolingual cohorts speak only one language.

Bilinguals have been posited to have, compared to monolinguals, enhanced cognitive control, consequently exhibiting greater cognitive reserve, which is thought to subsequently delay the onset of clinical expression of dementia. Based on recent evidence suggesting that the more languages one manages the greater cognitive reserve, and that trilinguals undergo greater exercise in language control than bilinguals, this thesis investigated the effects of trilingualism and ageing on cognitive control, in young adults to older adults. As the thesis investigated the novel field of trilingualism and cognitive control, task complexity, the age of second and third language acquisition, language use, and physical and cognitive activity were also, importantly, assessed, as these are possible influencing factors in test performance. The participants completed several cognitive tasks; namely the Simon task, the Inhibition of return task, the Stroop task (inhibition) and the N-back task (working memory). The novel discovery of a trilingual (and bilingual) disadvantage was observed, which could explain some previous inconsistent findings in the bilingualism literature, where trilingualism may influence bilinguals’ test performance, as trilinguals and multilinguals are often mixed in with the bilingual group. Furthermore, the results suggest that second language acquisition and language use does not consistently predict performance in trilinguals (and bilinguals), nor does cognitive activity, although physical activity may modulate language group differences. Importantly, the results from this novel investigation of the effects of trilingualism and ageing on cognitive control suggest that trilingualism (and bilingualism) can, in some cases, be detrimental to cognitive control.

Doctor of Philosophy / Department of Psychological Sciences / Heather R. Bailey / Bilingualism refers to an ability to speak two or more languages and the daily experience involved in coordinating these two languages can have a strong effect on bilinguals’ cognition. For decades, research strongly supported the idea of bilingual advantage; however, recent studies have found no bilingual advantage. Not surprisingly, such conflicting findings raised concerns about the validity of previous research as well as several other methodological issues. For instance, simple cognitive tasks like the Simon task are commonly used in bilingualism research, but they may not best capture bilinguals’ daily experience using the two languages. Bilinguals are constantly suppressing one language while engaged in other tasks, which is better captured by complex working memory (WM) tasks. Most importantly, previous work has not empirically evaluated the effects of language mode on bilinguals’ cognitive performance. Language mode refers to the state of activation of each language. Bilinguals may be in monolingual mode if only one of their languages is activated, whereas they may be in bilingual mode if both of their languages are activated. Previous work has proposed that language mode can have an effect on performance. Thus, the main objective of this dissertation was to evaluate the possible effects of bilingualism on complex WM performance while controlling for language mode and various demographic variables. The Pretest provided initial evidence that language mode affected performance on a simple cognitive task like MPWI. Therefore, a similar language mode manipulation was used in the Main study while testing performance on several complex WM tasks (CSPAN, OSPAN, and RotSpan) and the Simon task for monolinguals, bilinguals in bilingual mode, and bilinguals in monolingual mode. No significant differences were observed between all bilinguals and all monolinguals on any of the measures. However, significant differences were observed once language mode was accounted for. That is, bilingual participants in bilingual mode outperformed both bilingual participants in monolingual mode and monolingual participants on measures of complex WM. Further, there were no differences between monolinguals and bilinguals in monolingual mode. Thus, being in monolingual mode and fully suppressing one language may require more inhibition resources than bilingual mode in which both languages are active, and as a result, there may be fewer resources left to complete the complex WM span tasks. Importantly, the current work shed light on the hotly debated issue of the existence of a bilingual advantage by identifying a third variable that may explain the conflicting results in the literature. That is, no bilingual advantage was observed, but the current data provide evidence of a bilingual mode advantage.

Bilinguals have been posited to have, compared to monolinguals, enhanced cognitive control, consequently exhibiting greater cognitive reserve, which is thought to subsequently delay the onset of clinical expression of dementia. Based on recent evidence suggesting that the more languages one manages the greater cognitive reserve, and that trilinguals undergo greater exercise in language control than bilinguals, this thesis investigated the effects of trilingualism and ageing on cognitive control, in young adults to older adults. As the thesis investigated the novel field of trilingualism and cognitive control, task complexity, the age of second and third language acquisition, language use, and physical and cognitive activity were also, importantly, assessed, as these are possible influencing factors in test performance. The participants completed several cognitive tasks; namely the Simon task, the Inhibition of return task, the Stroop task (inhibition) and the N-back task (working memory). The novel discovery of a trilingual (and bilingual) disadvantage was observed, which could explain some previous inconsistent findings in the bilingualism literature, where trilingualism may influence bilinguals’ test performance, as trilinguals and multilinguals are often mixed in with the bilingual group. Furthermore, the results suggest that second language acquisition and language use does not consistently predict performance in trilinguals (and bilinguals), nor does cognitive activity, although physical activity may modulate language group differences. Importantly, the results from this novel investigation of the effects of trilingualism and ageing on cognitive control suggest that trilingualism (and bilingualism) can, in some cases, be detrimental to cognitive control.

Two conflicting findings characterize cognitive processing accompanying bilingualism. The “bilingual advantage” refers to improved cognitive performance for bilingual compared to monolingual participants. Most bilingual advantages fall under the umbrella of cognitive control mechanisms, most frequently demonstrated using the Stroop task and the Simon task (e.g., Bialystok, 2008; Coderre, Van Heuven, & Conklin, 2013). The “bilingual disadvantage,” on the other hand, refers to bilinguals’ diminished performance on tasks that require word retrieval or switching between languages. This study examined the intersection of the bilingual advantage and the bilingual disadvantage to investigate whether they stem from a single cognitive control process. The bilingual advantage was measured as speech onset time differences between monolingual and bilingual participants in the Stroop task after being primed in the same language (i.e., English prime and English Stroop for monolinguals, and either English prime and English Stroop or Spanish prime and Spanish Stroop for bilinguals). The bilingual disadvantage was measured as differences in bilingual participants’ speech onset times between the same-language conditions described above and cross-language conditions (i.e., either English prime and Spanish Stroop or Spanish prime and English Stroop). Monolinguals performed better than bilinguals did on the same-language Stroop [F(3,1) = 83.5, p < 0.001, MSE = 15415], so a bilingual advantage was not demonstrated. However, bilinguals did perform better in same-language blocks than cross-language blocks [F(7,3) = 24.6, p < 0.001, MSE = 22648]. This suggests that the current protocol successfully elicits the bilingual disadvantage. Further research is needed to evaluate whether the same cognitive control processes are responsible for the two effects. Possible extensions of this work include observing a larger number of participants to rule out between-subjects effects and using a button press rather than spoken response during the Stroop task.