Examining affective partisan polarization through a novel behavioral experiment: The equality equivalency test in the United States (2019–2022)

Existing behavioral studies of affective partisan polarization only capture a subset of decision-making preferences and strategies. We apply an innovative experimental design, the Equality Equivalency Test (EET), to investigate a broader range of affective behavior toward partisan others. Based on data from yearly nationwide surveys between 2019 and 2022 with over 6000 observations, we find that affective polarization is expressed through strong malevolent, and to a lesser degree, benevolent deviations from rational expected-utility maximization. The rising preponderance of spitefulness towards political opponents supports negative partisanship as the dominant mechanism governing affective polarization. In addition, we find evidence of growing negative partisanship among independents, who are turning increasingly spiteful toward members of both parties. We argue that the EET should be utilized by scholars as a next-generation design innovation to deepen our understanding of affective polarization.