Examining decision-making using transcranial direct current stimulation

INTERVENTION: Eldith tDCS stimulator device (DC Stimulator Plus); Participants will be assigned to one of two arms (each participant will undergo two sessions in total). For both arms, Session 2 will be scheduled at least 3 days after Session 1. Arm 1: Session 1: 20 minutes of transcranial Direct Current Stimulation (tDCS) at 2mA: anodal stimulation to left dorsolateral prefrontal cortex (DLPFC) (electrode placed at F3, based on the international 10‐20 system) and cathodal stimulation to right DLPFC (electrode placed at F4). Session 2: 20 minutes of sham (fake) tDCS (30 seconds of 2 mA tDCS, then current is switched off) to left DLPFC and right DLPFC. Arm 2: Session 1: 20 minutes of tDCS at 2mA: anodal stimulation to right DLPFC and cathodal stimulation to left DLPFC Session 2: 20 minutes of sham (fake) tDCS CONDITION: Decision‐making processes in healthy volunteers PRIMARY OUTCOME: Difference in the proportion of risky gamble choices made on a gambling task between active tDCS and sham tDCS ; ; The gambling task is a simplified version of slot‐machines or "pokies". On each trial participants will be given a number of betting options and asked to place a bet. Larger bets associated with larger wins. ; ; Risky gambling choices is defined as the proportion of trials in which participants decide the place the larger bet over the smaller bet. Difference in the proportion of unfair offers accepted (in Ultimatum Game experimental task) between active tDCS and sham tDCS SECONDARY OUTCOME: Anhedonia score (as measured by Principal Components Analysis score of Chapman Physical Anhedonia Scale, Chapman Social Anhedonia Scale, Snaith‐Hamilton Pleasure Scale, Temporal Experience of Pleasure Scale, Carver and White BIS/BAS scale) INCLUSION CRITERIA: No history of neurological or psychiatric illness; Not taking any psychoactive medications; Able to provide informed consent