No Change in Theory of Mind Related Processes During tDCS to the Right Temporoparietal Junction

Many studies report changes to social cognition after delivering transcranial direct current stimulation (tDCS) to the scalp. Across multiple paradigms, it is unclear whether changes in social cognition are a result of modulating fundamental cognitive processes, like attention-shifting, or multidimensional ones, like theory of mind. The aim of this study was to segment theory of mind into component processes and examine how tDCS modulates task performance in each to clarify the role of the temporoparietal junction in social cognition. Three stimulation conditions were used: anodal, cathodal, and sham. tDCS was applied to the right temporoparietal junction whilst participants completed the Reading the Mind in the Eyes Task, a shape association self-other distinction task, and the Wisconsin card-sorting task. Results showed no significant differences between anodal, cathodal, and sham tDCS conditions, as well as no significant change in task accuracy from before tDCS was applied to during tDCS being applied (p = .05). A significant difference in task performance was found between the three tasks. Exploratory analyses showed a significant, un-corrected task by stimulation by time point interaction, which is likely driven by the difference in task difficulty. The efficacy of tDCS remains unclear, and we highlight a potential file-drawer problem in this field.