Date Published: March 7, 2019
Publisher: Public Library of Science
Author(s): Rémi Radel, Mathieu Gruet, Krystian Barzykowski, Miguel A. Vadillo.
The observation that exerting self-control in an initial task impairs subsequent self-control performance in a following task has been used to explain a wide range of phenomena. If evidence for this “ego-depletion” effect was initially believed to be strong, it is now questioned. Recent meta-analyses indicated that this effect was sensitive to publication bias and that it was greatly reduced after control for this bias. In a pre-registered replication attempt where an ego-depletion protocol was conducted in multiple independent laboratories, the effect was not distinguishable from zero. Here, a different approach is adopted to examine the validity of this effect by improving the experimental protocol with the addition of important methodological precautions: 1) a pre-test measurement, 2) a learning period, 3) a prolonged depleting task, 4) a similar control condition, and 5) valid indexes of self-control. Accordingly, a well-learned Simon task was done before and after 1h of continuous practice of a Stroop task in a high inhibition demands condition (75% of incongruent trials) or in a control condition (0% of incongruent trials). Datasets from between-subjects (Study 1, N = 82) and within-subjects (Study 2, N = 52) experiments were analyzed using generalized linear mixed models. A significant ego-depletion effect was found in Study 1 (greater interference effect and accuracy decline in high inhibition demands than in control condition) but not in Study 2. Because it is difficult to explain this difference in results, the findings suggest that, even in a context chosen to optimize the observation of an ego-depletion effect, it seems difficult to be conclusive about the existence of this effect.
Self-control, commonly defined as the capacity to actively override impulses, to suppress urges, and to resist habits and temptations , is crucial for a large variety of activities and to achieve long-term goals and plans. However, it has been suggested that self-control is a finite resource that can be easily depleted . This « ego-depletion » perspective was formulated following the observation that exerting self-control in a first task led to an impaired ability to exert self-control in a second task . An impressive number of studies has then followed in this vein, testing a similar two sequential tasks protocol in a variety of contexts with the aim of explaining the occurrence of some maladaptive behaviors as a result of a self-control failure. Despite this large set of studies, it is however still impossible to be conclusive on the existence of an ego-depletion effect, and it has therefore been recommended to conduct additional research to indicate if this effect really exists [3,4].
The present research aimed at testing the existence of the ego-depletion effect using another approach by testing the presence of this effect in a context where we optimized the experimental conditions for the observation of this effect. To achieve this goal, we selected tasks that are known to mobilize self-control resources, chose a task duration that is long enough, and used precautions to minimize individual differences. We analyzed data from two different studies, a first study with a between-subjects design and a second study from a within-subjects design. The results were contrasted with different patterns of results in the two studies.
Taken together, our results suggest that when manipulating the level of inhibition demands during the practice of long and continuous task, we could not systematically observe an ego-depletion effect. In other words, even in a protocol that was designed to optimize the conditions of its occurrence, ego-depletion remains an elusive effect. For the future, we see value in additional research on ego-depletion but first recommend conceptual work to better define the cognitive attributes of self-control. For the moment, this study indicates that if self-control just relies on inhibitory control, then it might be hard to observe ego-depletion.