Hypnotic ingroup–outgroup suggestion influences economic decision-making in an Ultimatum Game

Studies in economic decision-making have demonstrated that individuals appreciate social values supporting equity and disapprove unfairness when distributing goods between two or more parties. However, this seems to critically depend on psychological mechanisms partly pertaining to the ingroup–outgroup distinction. Little is known as to what extent economic bargaining can be manipulated by means of psychological interventions such has hypnosis. Here we show that a hypnotic ingroup versus outgroup suggestion impacts the tolerance of unfairness in an Ultimatum Game. Specifically, the ingroup suggestion was associated with significantly greater acceptance rates of unfair offers than the outgroup suggestion, whereas hypnosis alone exerted only small effects on unfairness tolerance. These findings indicate that psychological interventions such as hypnotic suggestion can contribute to ingroup favoritism and outgroup rejection.