Personality trait and state associations with cognitive functioning and variability in middle and older adults

Personality characteristics are early indicators of later cognitive functioning, but existing studies primarily focused on trait-level trends. How well these between-person differences translate to risk-mitigating interventions remains unclear. Addressing this entails examining within-person differences that explain how states may accumulate over time to influence longer-term outcomes. The present study answers this by investigating associations between personality traits and states and momentary cognitive function and variability. We conducted a three-week ecological momentary assessment study of middle and older adults (N = 183). We used Bayesian Mixed-Effect Location Scale Models to capture contingencies between personality and momentary cognitive functioning and variability. We additionally explored machine learning via (elastic net regression) profiles of personality state-cognition contingencies to identify who experiences stronger associations. At the trait-level, higher conscientiousness was associated with poorer working memory and processing speed. Higher openness was associated with better cognitive functioning and lower variability for episodic memory and processing speed. At the state-level, conscientiousness was better for working memory performance, while neuroticism was associated with variable episodic memory functioning. Extraversion was associated with working and episodic memory functioning and variability. Finally, sociodemographic, health, and personality trait variables emerged as top predictors of individual differences in within-person associations. By investigating within-person associations between personality and cognitive ability, we demonstrate that trait-level associations do not necessarily generalize to state-level ones. Profiles of top predictors of individual differences in state-level associations may be promising targets for intervention, but interventions should be tailored with between- and within-person differences in mind.