The anger-infused ultimatum game: A reliable and valid paradigm to induce and assess anger

The Ultimatum Game (UG) is a canonical social decision-making task whereby a proposer divides a sum of money between himself and a responder who accepts or rejects the offer. Studies consistently demonstrate that unfair offers induce anger, and that rejecting such offers relates to aggression. Nevertheless, the UG is limited in interpersonal provocations common to real-life experiences of anger. Moreover, the psychometric properties of the UG as an anger-induction paradigm have yet to be evaluated. Here, to induce a more intense and genuine anger experience, we implemented a modified UG whereby short written provocations congruent with unfairness levels accompanied each offer. We aimed to test whether this anger-infused UG led to more anger and aggressive responses relative to the standard UG and to establish the reliability and validity of both versions. Participants performed either the anger-infused UG or a standard version, repeated twice, a week apart. They also performed the Taylor Aggression Paradigm, a reactive aggression paradigm, and completed emotion ratings and a trait anger inventory. Results indicate similar decreases in acceptance rates with increase in offer unfairness, and increases in reported anger, across both UG versions. Both versions demonstrated strong test-retest reliability. However, the anger-infused UG led to significantly stronger relations with reactive aggression and trait anger compared to the standard UG, providing evidence for better validity. The development of the anger-infused UG as a reliable and valid paradigm is pivotal for the induction and assessment of interpersonal anger and its aggressive expression in basic and clinical research settings.