Sometimes you just can't: within-person variation in working memory capacity moderates negative affect reactivity to stressor exposure.

The executive hypothesis of self-regulation places cognitive information processing at the center of self-regulatory success/failure. While the hypothesis is well supported by cross-sectional studies, no study has tested its primary prediction, that temporary lapses in executive control underlie moments of self-regulatory failure. Here, we conducted a naturalistic experiment investigating whether short-term variation in executive control is associated with momentary self-regulatory outcomes, indicated by negative affect reactivity to everyday stressors. We assessed working memory capacity (WMC) through ultra-brief, ambulatory assessments on smart phones five times per day in a 7-day ecological momentary assessment (EMA) study involving college-aged adults. We found that participants exhibited more negative affect reactivity to stressor exposures during moments when they exhibited lower than usual WMC. Contrary to previous findings, we found no between-person association between WMC and average stress reactivity. We interpret these findings as reflecting the role of executive control in determining one's effective capacity to self-regulate.