Gender differences in cognitive Theory of Mind revealed by transcranial direct current stimulation on medial prefrontal cortex

Abstract

Gender differences in social cognition are a long discussed issue, in particular those concerning Theory of Mind (ToM), i.e., the ability to explain and predict other people's mental states. The aim of this randomized, double-blind, placebo-controlled study was to test the hypothesis that anodal tDCS over the medial prefrontal cortex (mPFC) selectively enhances cognitive ToM performance in females. In the first experiment we administered to sixteen females and sixteen males a cognitive ToM task during anodal or placebo tDCS over the mPFC. In the second experiment further sixteen females completed the task receiving anodal or placebo tDCS over the vertex. The results showed that anodal tDCS over the mPFC enhances ToM in females but not in males, an effect indicated by enhanced ToM in females that received anodal tDCS over the mPFC compared with females that received tDCS over the vertex. These findings are relevant for three reasons. First, we found evidence of gender-related differences in cognitive ToM, extending previous findings concerning affective ToM. Second, these differences emerge with anodal stimulation of the mPFC, confirming the crucial role of this area in cognitive ToM. Third, we show that taking into account gender-related differences is mandatory for the investigation of ToM.

Figure 1. Changes in RTs in the AI task for anodal tDCS and placebo tDCS.

Only in the female group that received tDCS over mPFC the RTs were improved after anodal tDCS compared to placebo stimulation. No tDCS effects were shown for the female group that received tDCS over Cz and for the male group that received tDCS over mPFC. No significant differences between the groups were observed in the placebo condition. Asterisk indicates a significant effect (p < 0.05).

Figure 2

(A) Experimental design. Anodal or placebo tDCS was applied 2 minutes before the beginning of the experimental block and covered the entire AI task. In the AI task, a short video was played and then the participant’s task was to choose the picture showing the logical story ending, by pushing one of the two buttons on a button box. (B) Schematic drawing of electrode positions.