Mind wandering (MW) is a common mental phenomenon. Despite this, there is still much we don’t know about this pervasive mental state. Transcranial direct current stimulation (tDCS) has been proposed to be able to modulate mind wandering propensity, but a large variability in results paints an inconclusive picture in the current brain stimulation literature, and a satisfactory conclusion is still lacking. Recently, a study by Boayue et al. (2020) reported to successfully reduce mind wandering using high-definition transcranial direct current stimulation (HD-tDCS) over the dorsolateral prefrontal cortex, providing preliminary evidence of the efficacy of HD-tDCS in modulating MW. The current thesis introduces the topic of replicating this elusive effect of non-invasive brain stimulation in depth, as well as reporting a high-powered, pre-registered direct replication attempt of the effect found by Boayue et al. (2020). Additionally, the results of investigating MW with a finger-tapping random sequence generation task that draws heavily on executive resources are reported. We failed to replicate the original effect of reducing MW during HD-tDCS, and in a meta-analytic approach, when the data was combined with Boayue et al. (2020) the original effect of HD-tDCS reducing MW disappeared. These findings and potential problems of brain stimulation studies (in particular their low replicability) and their implications are reviewed and discussed
