Project Summary The burden of Alzheimer’s Disease (AD) takes a significant toll on the individual living with dementia, their families and communities, and the healthcare system. Without effective intervention and prevention strategies, the prevalence of AD is expected to more than double over the next 30 years. It is critical to identify protective factors that can be leveraged for more effective prevention before the onset of the disease. Conscientiousness is a personality trait that is associated consistently with better health outcomes, which extends to dementia: Conscientiousness is one of the most replicated psychological factors that is protective against cognitive impairment. Most work on Conscientiousness has focused on its agentic aspects (e.g., self-control, achievement striving). Conscientiousness, however, has a distinct interpersonal component that is often overlooked in the relation with health in general and cognition in particular. This interpersonal component – Interpersonal Conscientiousness – defined as either responsibility or dutifulness, is protective against dementia, an effect that has replicated in three independent samples. In addition, its protective association with dementia is independent of the agentic components of this trait and extends to cognitive function prior to dementia. Interpersonal Conscientiousness is thus a robust and novel psychological factor that is a promising target of intervention for healthier cognitive outcomes in older adulthood. The objective of this proposal is to provide much needed stage 0 evidence that is necessary for intervention development. Specifically, this research aims to identify the clinical/physiological, behavioral, psychological, and relational mechanisms through which Interpersonal Conscientiousness leads to better cognitive outcomes. The proposed research addresses these mechanisms and cognition as typically measured in lab settings and the daily expression of these mechanisms and momentary cognitive performance measured with ecological momentary assessment in everyday life. It seeks to identify the pathways through which Interpersonal Conscientiousness protects cognition and promotes better daily cognitive function across a critical period of the lifespan – midlife and the transition to old age (ages 40-70) – a period particularly relevant for prevention because it is generally before the onset of neurodegeneration. In addition, this research addresses actor and partner effects within committed relationships to test whether the protective effect of Interpersonal Conscientiousness extends from one member of the couple to the other. This work will lead to new knowledge on how Interpersonal Conscientiousness promotes healthier cognitive aging and will point to new prevention and intervention targets for promoting healthier cognitive aging across adulthood to support better outcomes in older adulthood.