 Ultimate explanations, on the other hand, aim to explain the likely origins of different traits. It is now common for the cognitive sciences to make extensive use of evolutionary theory, taking what is known about the environments and selective pressures faced by ancestral populations and using it to help inform hypotheses about minds (Barkow, Cosmides, &amp; Tooby 1992). Central to many of the ultimate explanations proposed by researchers interested in the psychology of norms are the adaptive challenges raised by collective action and large-scale cooperation (Gintis, Bowles, et al. 2005; Boyd &amp; Richerson 2005b; N. Henrich &amp; J. Henrich 2007; Tomasello 2009). For the sake of clarity, it is helpful to remember that these two styles of explanation are analytically distinct, but that proximate and ultimate explanations for a given trait will ideally be complementary and mutually reinforcing. Thus, evolutionary accounts of norm cognition can inform and constrain proximate models, and vice versa.