Moral rigidity as a proximate facilitator of group cohesion and combativeness.

De Dreu and Gross’s description of the proximate mechanisms conditioning success in intergroup conflict omits humans’ deontological morality. Drawing on research on sacralization and moral objectivism, I show how “moral rigidity” may have evolved through partner selection mechanisms to foster coalitions’ cohesion and combativeness in intergroup conflict [corrected]. De Dreu and Gross's argument that attack and defense are distinct strategies underpinned by different neuropsychological circuitries is an original refinement of the theory of conflict. However, their description of the proximate mechanisms facilitating success in intergroup competition (sect. 4, target article) omits humans' deontological moral intuitions. In interaction with overconfidence biases, hostile attributions, and the enforcement of "cultural rituals and sanctioning systems" (sect. 4, para. 1), what may crucially help groups of individuals cohere and prevail in conflict are high levels of "moral rigidity" in their tribal members, that is, of inflexible loyalty to their interpersonal commitments within the group.