The effects of alcohol on sequential decision-making biases during gambling

Rationale: Gambling and alcohol use are recreational behaviours that share substantial commonalities at a phenomenological, clinical, and neurobiological level. Past studies have shown that alcohol can have a disinhibiting effect on gambling behaviour, in terms of bet size and persistence. Objectives: To characterize how alcohol affects biases in judgment and decision-making that occur during gambling, with a focus on sequential decision-making including the gambler’s fallacy. Methods: Sequential biases were elicited via a roulette-based gambling task. Using a standard between-groups alcohol challenge procedure, male participants played the roulette task 20 minutes after receiving an alcoholic (0.8g/kg; n = 22) or placebo (n = 16) beverage. The task measured colour choice decisions (red/black) and bet size, in response to varying lengths of colour runs and winning/losing feedback streaks. Results: Across both groups, a number of established sequential biases were observed. On colour choice, there was an effect of run length in line with the gambler’s fallacy, which further varied by previous feedback (wins vs losses). Bet size increased with feedback streaks, especially for losing streaks. Compared to placebo, the alcohol group placed higher bets following losses compared to wins. Conclusions: Increased bet size after losses following alcohol consumption may reflect increased loss chasing that may amplify gambling harms. Our results do not fit a simple pattern of enhanced gambling distortions or reward sensitivity, but help contextualize the effects of alcohol on gambling to research on decision-making biases.