Do different fairness contexts and facial emotions motivate ‘irrational’ social decision-making in major depression? An exploratory patient study

Although ‘irrational’ decision-making has been linked to depression, the contribution of biases in information processing to these findings remains unknown. To investigate the impact of cognitive biases and aberrant processing of facial emotions on social decision-making, we manipulated both context-related and emotion-related information in a modified Ultimatum Game. Unfair offers were (1) paired with different unselected alternatives, establishing the context in which an offer was made, and (2) accompanied by emotional facial expressions of proposers. Responder behavior was assessed in patients with major depressive disorder and healthy controls. In both groups alike, rejection rates were highest following unambiguous signals of unfairness, i.e. an angry proposer face or when an unfair distribution had deliberately been chosen over an equal split. However, depressed patients showed overall higher rejection rates than healthy volunteers, without exhibiting differential processing biases. This suggests that depressed patients were, as healthy individuals, basing their decisions on informative, salient features and differentiating between (i) fair and unfair offers, (ii) alternatives to unfair offers and (iii) proposers' facial emotions. Although more fundamental processes, e.g. reduced reward sensitivity, might underlie increased rejection in depression, the current study provides insight into mechanisms that shape fairness considerations in both depressed and healthy individuals.