Dissertations, Theses, and Capstone Projects

Date of Degree

9-2025

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy

Program

Psychology

Advisor

Justin Storbeck

Committee Members

Veronica J. Hinton

Sarah Grey

Desiree Byrd

Melinda Cornwell

Subject Categories

Clinical Psychology | Cognitive Psychology | First and Second Language Acquisition

Keywords

multilingualism, bilingual advantage, set-shifting, cognitive flexibility, rumination

Abstract

Although findings are mixed, many researchers believe there are cognitive benefits to multilingualism, a phenomenon dubbed the “bilingual advantage”. Of these apparent benefits, cognitive flexibility, or the ability to shift thinking styles based on the context or specific demands of a certain situation, is thought to be highly relevant. Current literature suggests that one aspect of multilingualism, the practice of “code-switching” between languages throughout their daily lives, is related to increased general cognitive flexibility compared to monolinguals. Another branch of research on cognitive flexibility investigating the role of affect in cognition demonstrates that clinical depression as well as transient negative affective states are related to decreased cognitive flexibility. For example, many people with depression or in sad moods tend to be vulnerable to rumination or repetitive negative thinking patterns. This study examined whether multilingualism serves as a protective factor against cognitive impairments associated with negative mood and rumination, particularly in the context of cognitive flexibility. Across two experiments, participants completed a cognitive set-shifting task following a mood induction (negative or neutral) and provided self-report data on depression, rumination, and cognitive flexibility. We hypothesized that multilingual individuals would demonstrate superior performance on the set-shifting task, even when induced into a sad mood (Experiment 1), or when they had higher depressive symptomatology (Experiment 2). In general, we predicted that multilingualism would buffer against mood-induced deficits in cognitive functioning. Contrary to predictions, multilingualism was overall not associated with advantages in cognitive functioning, either on self-reported outcomes or on performance on a cognitive set-shifting task. In fact, correlational results of Experiment 1 suggested that multilingualism was associated with slower reaction time (RT) on switch trials of the set-shifting task, as well as increased state rumination. When multilingualism did benefit cognitive flexibility, it was detected only in specific favorable conditions, such as when trait rumination and depressive symptomatology was low, and under neutral mood induction. This subtle advantage benefitted accuracy on the cognitive set-shifting task, and not reaction time. No main effects or two-way interactions among multilingualism, mood condition, and psychological factors predicted cognitive performance. However, several three-way interactions emerged of multilingualism, trait rumination, and mood induction condition, and multilingualism, depressive symptomatology, and mood induction condition. Notably, multilinguals with low trait rumination in a negative mood state performed worse than monolinguals on switch trials, contradicting the hypothesized protective effect. In contrast, under neutral mood and low trait rumination, multilinguals outperformed monolinguals on backward inhibition (BI) and switch trials. These findings suggest that any cognitive benefits of multilingualism are limited and conditional, rather than generalizable. These results challenge the assumption of a universal bilingual advantage.

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