A preference for sameness and associated positive emotions in interindividual discrimination, even when based on chance

It was recently demonstrated that people allocate more money to another person when they both demonstrate the same outcome versus a different one, even when the outcome is based on chance. Different theoretical frameworks predict whether this effect reflects a preference for sameness, a derogation of difference, or both. Across three preregistered online experiments, we employed dot estimation (Exp. 1, n = 75), painting preference (Exp. 2, n = 75), and coin flip (Exp. 3, n = 84) versions of the sheer difference paradigm, while introducing a condition that lacked congruency information to distinguish these effects. Additionally, in the coin flip task, we explored retrospective emotional responses (using a self-report rating scale and the Positive and Negative Affect Schedule-Short Form). We found that: (1) allocations in the sameness (congruent) condition were significantly higher than in the congruency-unknown and difference (incongruent) conditions (Exp. 1–3); and (2) participants reported more positive emotions in the congruent condition than in both the congruency-unknown and incongruent conditions (Exp. 3). Notably, the congruency effect in retrospective positive emotion ratings was also significantly correlated with the congruency effect in allocation measures. We discuss the use of congruency-unknown conditions in this study and in the wider literature to disentangle preference for sameness from derogation of difference. This study provides a clearer understanding of unequal allocation following interpersonal sameness versus difference, while also offering preliminary evidence for their relationship with emotions.