The role of task similarity for ego depletion: a registered report

Ego depletion refers to decrements in self-control performance resulting from prior use of self-control. The ego depletion effect has received much research attention, but the more recent literature reports small or null effects. This registered report examined the moderating effect of task similarity on the ego depletion effect. We predicted a crossover interaction between type of primary and secondary task such that engaging in a demanding self-control task should lead to better performance in the secondary task when it is similar to the primary task (facilitation effect) but worse performance when it is dissimilar (ego depletion). In a preregistered pilot study, N = 80 participants first completed either a visual stop-signal task (SST) or a simple lexical categorization task. They proceeded with one of four tasks classified as increasingly dissimilar based on their underlying operations and executive functions: (1) auditory stop-signal task, (2) Stroop task, (3) Eriksen flanker task, and (4) unsolvable anagrams. Both the pilot study and a high-powered registered replication (N = 300) revealed the predicted interaction effect. However, evidence for facilitation from similar tasks was stronger than evidence for depletion from dissimilar tasks. Together, these findings highlight the important role of task similarity for the study of ego depletion and related phenomena.