Fig. 1: Experimental design and choice behavior.

a Trial structure. Each trial consisted of a choice task and a confidence rating, followed by a challenge and feedback. In the choice task, participants had to decide whether to accept or reject a given offer based on gain prospects (represented by a set of regular 10 cent coins) and loss prospects (crossed-out 10 cent coins). The challenge involved stopping a moving ball, which became invisible upon entering a gray tunnel, within the blue target (difficulty level) in the center of the screen. b Stimulation procedure. Each session consisted of 14 trials with intracranial electrical stimulation (iES) alternating with 14 trials without iES. The nature of the first trial (with or without iES) was randomly assigned to maintain participants’ blindness to the experimental conditions. A 30-s interval was observed between the onset of each trial, resulting in a 1 min interval between each stimulation. During trials involving iES, stimulation was delivered for a period of 5 s, in the form of pulses with a width of 0.5 ms, at a frequency of 50 Hz and an amplitude of 1, 2, or 3 mA (adjusted to ensure that participants did not experience any discernible clinical effects or subjective sensations during the task). c Anatomical location of the anterior insula (aIns; pink) and ventromedial prefrontal cortex (vmPFC; green) stimulation sites retained for analysis on the standard Montreal Neurological Institute (MNI) template brain. Anterior (A), posterior (P), dorsal (D) and ventral (V) directions are indicated. Stimulation sites have been aggregated in the mediolateral direction (x-axis) for visualization purposes. See Supplementary Fig. 1 and Supplementary Table 1 for a more detailed location of each site. d Choice behavior in trials without iES. Acceptance probability is plotted as a function of the monetary prospects (gain and loss) and confidence (expressed as percentile). Circles represent binned data averaged across stimulation sites. Error bars represent S.E.M across stimulation sites. Significant main effects of gains (t₇₇₂ = 4.24, p < 0.001), losses (t₇₇₂ = −4.26, p < 0.001), and confidence (t₇₅₈ = 2.23, p = 0.026) on acceptance probability were found using logistic mixed-effects models with participants (n = 15 for gains and losses / n = 14 for confidence) and stimulation sites (n = 54 for gains and losses / n = 53 for confidence) as random effects. *p < 0.05, ***p < 0.001.