The perception-behavior dissociation in the ultimatum game in unmedicated patients with major depressive disorders.

Jin, Gao, Wang, Xiao, Wu, & Zhou (2022) examined “The perception-behavior dissociation in the ultimatum game in unmedicated patients with major depressive disorders” in an article in Journal of Psychopathology and Clinical Science.  The ultimatum game is an experimental game in which one player (the proposer) makes an offer to another player (the responder) concerning a sum of money that the two must apportion between them, and the responder must then either accept or reject this offer. If the offer is accepted, the money is split as proposed. Jin et al. begin by noting that people with major depressive disorder (MDD) have a

lower acceptance rate of unfair proposals in the Ultimatum Game (UG) compared with a control group. They studied 68 unmedicated patients with MDD and 55 control group members. Here’s part of the abstract:

Fairness perception mediated the relationship between fairness level and acceptance behavior for both groups of participants when they played with human proposers but not computer proposers. The mediation effect was stronger among the control group than among the MDD patients. The linkage between fairness perception and acceptance behavior was attenuated among the patients with MDD compared with the control group. In conclusion, MDD patients were impaired in their ability to flexibly adjust acceptance behavior based on fairness perception in social interactions. 

There are several interesting findings here. First, fairness perception plays a mediating role only with human, not computer partners. Second, people in the control group used fairness perception more than depressed people did. Third, people with MDD were less able to use fairness perception as a basis for drawing inferences. Gradin et al. (2015) used fMRI research to examine the behavior of depressed people using the Ultimatum Game and offer additional insight:

In comparison to controls, depressed participants reported decreased levels of happiness in response to 'fair' offers. With increasing fairness of offers, controls activated the nucleus accumbens and the dorsal caudate, regions that have been reported to process social information and responses to rewards. By contrast, participants with depression failed to activate these regions with increasing fairness, with the lack of nucleus accumbens activation correlating with increased anhedonia symptoms. Depressed participants also showed a diminished response to increasing unfairness of offers in the medial occipital lobe.

Our findings suggest that depressed individuals differ from healthy controls in the neural substrates involved with processing social information. In depression, the nucleus accumbens and dorsal caudate may underlie abnormalities in processing information linked to the fairness and rewarding aspects of other people's decisions.