Day-to-day fluctuations in cognitive precision predict the domain-general intention-behaviour gap

The idea that better cognitive functioning helps to close the gap between goals and behaviour seems self-evident, yet empirical work has found surprisingly weak inter-individual associations between cognitive task performance and real-world, goal-relevant outcomes. Here, we resolve this paradox by shifting from trait-level to state-level assessments of cognition. Leveraging a micro-task design to measure daily fluctuations in cognitive function, goal setting and goal progress, mood, sleep, and motivation over a 12-week intensive longitudinal study of university students (N=184, timepoints=9,248), we show that within person upswings in domain-general information processing precision precede and predict same-day self-reported goal achievement across domains, even after controlling for other factors. A one standard deviation change in this cognitive capacity translated to the behavioral equivalent of ~40 minutes of work, with similar or larger predictive effects compared to fluctuations in mood/motivation and no moderation by trait-level self-control or conscientiousness. Our work addresses long standing controversies and highlights the power of intra individual analysis to reveal relationships missed by cross sectional approaches.