¿Por qué morir por un hermano?: La asociación positiva entre la fusión de identidad y la pérdida imaginada con la disposición al autosacrificio

Identity fusion — a visceral feeling of connection with a group — is a powerful predictor of willingness to engage in extreme pro-group behaviour. Here we propose that identity fusion also reinforces willingness to fight and die for one’s siblings, and we explore one of the underlying mechanisms producing this effect. We additionally controlled for a powerful predictor of family investment, perceived psychological similarity with the sibling. Our study shows that fusion with a sibling, but not perceived similarity, is positively associated with willingness to fight and die for the sibling. This relation is mediated by the imagined personal consequences of losing one’s sibling. This research extends previous work on fusion with groups to pairs of individuals and identifies a new mediator of the effect of fusion on willingness to fight and die for others. Overall, these results suggest that identity fusion might contribute towards explaining self-sacrifice among genetically related individuals as predicted by the theory of kin selection.