Self-reported cognitive confidence and negative beliefs about thinking predict metacognitive sensitivity in a pilot transcranial direct current stimulation (tDCS) experiment

Metacognition encompasses the capability to monitor and control one’s cognitive processes. According to brain imaging, prospective and retrospective second-order judgments recruit widespread portions of prefrontal cortex (PFC), thus leaving the neuronal architecture underlying metacognitive knowledge poorly understood. This pilot experiment makes use of transcranial Direct Current Stimulation (tDCS) targeting the ventromedial PFC (vmPFC) to understand whether this brain region occupies a crucial role in sustaining metacognition. A randomized, double-blind, within-subjects research design was used. Twelve healthy participants underwent two sessions of either anodal or sham tDCS over vmPFC spaced at least one week apart. During neuromodulation, subjects performed a 2-Alternative Forced Choice task with the addition of post-decisional confidence judgments. Metacognitions Questionnaire-30 was also dispensed at the beginning of each session, before applying neurostimulation. Wilcoxon signed rank test highlighted no statistically significant difference in metacognitive sensitivity between real and sham conditions. Linear mixed-effect model showed that metacognitive sensitivity was significantly predicted by self-reported negative beliefs about thinking (𝛘2(1) = 4.56, p = .033) and cognitive confidence (𝛘2(1) = 4.09, p = .043) regardless of stimulation protocol. Neuromodulation of vmPFC does not affect metacognition, suggesting that such brain region is not involved in retrospective second-order judgments. Hence, retrospective metacognitive judgments might recruit more lateral aspects of PFC, leaving to medial PFC the processing of prospective second-order judgments. Notably, self-reported beliefs concerning cognition impact on metacognition, hinting that higher levels of cognitive confidence might enhance one’s metacognitive sensitivity, whereas perceived danger or uncontrollability of thoughts could sort the opposite effect.