PROJECT SUMMARY. There are pervasive negative stereotypes about older adults’ competence, and these pose a barrier to successful aging by making older adults vulnerable to prejudice, discrimination, and stereotype threat. This project focuses specifically on the adverse effects of age-based stereotype threat (ABST). We define ABST as occurring when people are placed in situations that cause them to worry about the possibility of confirming (or being judged in light of) a negative age-based stereotype. Problematically, there is now more than two decades of research showing that when older adults experience ABST they underperform on cognitive tests, including on the tests used in clinical settings to assess for cognitive decline and dementia, and this likely contributes to an overdiagnosis of early dementia or mild cognitive impairment in older adults. ABST is also associated with poorer health, increased loneliness and depression, and greater dependency in older adults. There is a critical need to develop effective ABST interventions. In doing so, the NIH Stage Model of Behavioral Intervention Research suggests that intervention development should draw upon primary research that identifies the mechanism(s) underlying the effect of interest. Unfortunately, even though the adverse effects of ABST are well-documented and ubiquitous, there is debate about their underlying mechanisms, which poses a barrier to intervention development. Within the literature, there is currently support for two competing ABST theoretical models – namely, the executive control interference account and the regulatory focus account. In an effort to better understand ABST mechanisms, researchers have often pitted competing predictions from these two accounts against one another. However, this approach precludes the possibility that both theoretical accounts are correct, and that ABST effects occur for multiple reasons. To address this possibility, we will be the first to use a well-validated computation model (i.e., the drift diffusion model) to examine how ABST affects the component processes of older adults’ working memory performance (i.e., the domain where ABST effects occur most robustly). Within this innovative approach, predictions from the two ABST theoretical accounts do not contradict one another, and it is therefore possible to obtain support for one, or both, of them. Disentangling hypotheses from these accounts is a key strength of our approach, and this project will thus provide the most nuanced understanding to date of why ABST effects occur. Another strength of this approach is the recognition that ABST effects may not be explained by any single mechanistic account, and may instead be due to a cascade of attentional, physiological, affective, and motivational processes that together impact performance. The knowledge gained from this NIH Stage 0 (basic research) project about why ABST effects occur will directly inform future ABST intervention work. For insta...