Undergraduate Honors Theses

Thesis Defended

Spring 2018

Document Type


Type of Thesis

Departmental Honors



First Advisor

Akira Miyake

Second Advisor

Michael Saddoris

Third Advisor

Andrew Chapman


The ego-depletion effect was originally found to be highly robust and has often been explained through the strength model of self-control. This model states that exerting self-control depletes a limited pool of domain-general resources and makes subsequent self-control attempts less effective. However, some researchers proposed an alternative account based on the notion of people’s implicit beliefs about willpower; specifically, only those individuals who hold the belief that willpower is limited are susceptible to the ego-depletion effect. This study evaluated these two theoretical accounts of the ego-depletion effect while trying to address some of the methodological and conceptual limitations present in most prior research. The current study used the sequential-task paradigm on two 20-minute tasks (N-back and SART) that have been shown to overlap in their self-control task demands. N-back task differed in their self-control demands where the easy 1-back version was administered in the non-depletion condition and the more challenging 2-back version in the depletion condition. It was hypothesized that if the strength model is valid, there should be more inhibitory errors and attentional lapses in the second SART task. Further, it was hypothesized that if the mindset theory is valid, the ego-depletion effect should be moderated by one’s belief about willpower. The preliminary results based on 98 subjects (n = 49 in each condition) showed that there were no significant differences in SART performance or mind wandering between conditions. Further, no significant interactions were found between beliefs about willpower and condition. These findings do not only challenge both the strength model and willpower belief accounts of the ego-depletion effect but more fundamentally add to the growing body of research that questions the robustness and replicability of the ego-depletion effect.