Fluctuations in emotional valence and arousal are differentially linked to cognitive performance and subjective mental effort.

Emotional states fluctuate continuously, yet it remains unclear how momentary emotional states and their temporal variability relate to cognition in daily life. We examined how fluctuations along the two principal dimensions of emotion, valence and arousal, are associated with objective cognitive performance and subjective mental effort using ecological momentary assessment. To address this question, we conducted two complementary studies. In Experiment 1 (online sample, n = 289), four brief state items (happiness, calmness, energy, fatigue) were validated as measures of state valence and arousal using a semantic association task and factor analysis. In Experiment 2, participants (July 2024-February 2025; n = 59) completed a 5-day ecological momentary assessment protocol with three assessments per day (682 completed sessions), combining repeated emotional state ratings with a working memory task and subjective mental effort reports. Associations were tested using linear mixed models. In Experiment 1, happiness and calmness loaded on a valence factor, whereas energy and fatigue loaded on an arousal factor. In Experiment 2, greater between-day variability in valence was associated with reduced working memory performance, driven by increased intrusion errors, together with lower perceived mental effort. In contrast, higher momentary arousal was associated with lower perceived mental effort without changes in working memory performance. Together, our results support a dissociation between emotional influences on cognitive control and on the subjective experience of effort. This dissociation suggests that emotion-cognition interactions in everyday life cannot be captured by a single affective dimension and that different emotional dimensions exert distinct effects on cognitive performance and its subjective experience. (PsycInfo Database Record (c) 2026 APA, all rights reserved).