Unfairness sensitivity and equity in severe alcohol use disorder: Insights from the ultimatum game

Severe alcohol use disorder (SAUD) is characterized by social interaction difficulties that play a key role in the persistence of this addictive state. Biased social decision-making might underpin such interpersonal problems. Previous studies exploring social decision-making in SAUD used the ultimatum game - an economic game evaluating sensitivity to unfairness (for the responder) and equity (for the proposer) - and showed increased unfairness sensitivity in SAUD. However, these studies used one-shot designs that are not representative of real-life interactions and focused only on responders, letting much of the phenomenon unexplored.

Thirty-five recently detoxified patients with SAUD and 34 matched control participants played four iterated ultimatum games, with variations according to the role (responder vs. proposer) and strategy used by their virtual opponent (fair/easy vs. unfair/difficult). Participants then completed social cognition tasks and psychopathological questionnaires.

As responders, patients with SAUD did not reject fair or unfair offers more often than controls, which contradicts the unfairness sensitivity previously highlighted in one-shot ultimatum games. As proposers, patients with SAUD made more generous offers than controls and did not adapt to their opponent's strategy, which resulted in poorer economic outcomes.

Patients with SAUD do not display an unfairness sensitivity but are less able to adapt to their opponent, which has detrimental consequences, namely poorer outcomes. They behave differently during one-shot and repeated interactions, probably because - due to their social cognition impairments - they need more time to understand their opponent and overcome their a priori social biases.