Executive Function Skills in English Monolinguals and Mandarin-English Bilinguals

Thesis (Master's)--University of Washington, 2019Previous studies have shown a relationship between one’s language background and executive function skills. Thus far, evidence has suggested that bilinguals may have a cognitive advantage compared to monolinguals in inhibition and shifting abilities. Some studies have shown that bilingualism has a positive correlation with inhibition and shifting abilities while other studies have shown mixed or no differences between monolinguals and bilinguals. For this study, our aim is to further delve into this controversial topic and replicate previous studies to examine the effects of bilingualism on executive function skills. We recruited a group of adult English monolingual (N=22) and Mandarin-English bilinguals (N=22), and compared their executive function skills measured by four tasks: Simon, Stroop, Letter-Number Switching and Color-Shape Switching (Cued). Two dependent measures were calculated and analyzed from these tasks: reaction time and percentage accuracy. We hypothesized that the bilinguals would outperform monolinguals on all tasks. Two-way mixed ANOVAs revealed mixed results between monolinguals and bilinguals across trial types. Results from the Simon task revealed that both groups responded significantly faster to compatible trials than incompatible trials, though both groups were similarly accurate in both trial types. Bilinguals also responded significantly slower than monolinguals to both trial types while a significantly larger difference was found between trial types in monolinguals than bilinguals. Results from the Stroop task revealed that both groups responded significantly faster and were more accurate in responding to compatible trials than to incompatible trials. However, no group differences or interaction effect were found. Results from the Letter-Number Switching and Color-Shape Switching (Cued) task revealed that both groups responded significantly faster and were more accurate in responding to repeat than to switch trials. Bilinguals also had a significantly higher accuracy percentage than monolinguals in the Letter-Number Switching task though no significant group differences were found in reaction time. No significant group differences were found in both dependent measures for the Color-Shape Switching (Cued) task. We discussed current results in relation to previous studies in terms of similarities and differences in methodology as well as potential confounding variables. We also discussed the limitations of our current study. In summary, while our results did not replicate previous research, it added to the existing literature on whether bilingualism affects inhibition and shifting skills and future research is warranted to address the methodological differences and potential confounding variables in cognitive tasks