Serum omega-3 fatty acids are associated with ultimatum bargaining behavior

Abstract

In the ultimatum game (UG), two players are involved to bargain over a division of a given sum of money. The proposer makes an ultimatum offer of a fraction of money, while the responder can either accept or reject the proposer's decision. In case of rejection of the proposed splitting by the responder, neither player gets anything. Adverse psychological reactions are deemed to play a role in the rejection of unfair offers. Low serum levels of omega-3 polyunsaturated fatty acids have been linked to impulse control and hostility. This study examined the serum omega-3 and omega-6 fractions in relation to the ultimatum bargaining behavior. Participants were sixty economy students (31 males and 29 females, mean age: 24.4 ± 2.3 years) who played a €10 ultimatum game. Ultimatum offers were constrained to be €5 (proposer keeps €5) or €1 (proposer keeps €9) to generate a roughly even split between fair (5:5) and unfair (1:9) offers. Fasting serum alpha-linolenic (ALA), eicosapentaenoic (EPA), docosahexaenoic acid (DHA), linoleic acid (LA) and arachidonic acid (AA) were assayed with gas chromatography. In participants who rejected unfair offers there was a significant depletion of ALA, EPA and DHA. Moreover, the ratio of serum omega-3/omega-6 fatty acids was significantly lower in patients who rejected unfair offers as compared to those who did not. The results of this study suggest that a depletion of the serum omega-3 fatty acids is associated with rejections of unfair ultimatum offers in an experimental neuroeconomic setting.