Self-Control Following Prior Exertion: An Empirical Test of the Motivational Shift and Compensatory Effort Hypotheses

The ego depletion effect—a sometimes-observed reduction in self-control performance following repeated self-control exertion—has been a topic of debate for over a decade. While a multitude of models have aimed to explain the effect, two prominent hypotheses are the focus of the current research: 1) the motivation shift hypothesis and 2) the compensatory effort hypothesis. So far, the mechanisms underlying both hypotheses (i.e., differences in exerted mental effort resulting from depletion and motivation) have not been tested and compared empirically. In a pre-registered experiment (N = 172), we manipulated depletion and motivation (presence of incentives) and physiologically assessed participants’ mental effort via systolic blood pressure (SBP) reactivity. Both hypotheses predict an interaction of depletion and motivation for mental effort, albeit with differing patterns. The results indicated that neither mental effort nor performance corresponded to either hypothesis. Instead, performance was consistent across all four conditions, with mental effort being predicted solely by the level of incentive. Both manipulation checks—self-reported depletion after the initial demand block and SBP reactivity during it—provided strong support for a successful depletion manipulation. Consequently, we conclude that these findings add to the growing body of evidence challenging the ego depletion effect empirically as well as its theoretical foundations.