Pietraszewski proposes four triadic “primitives” for representing social groups. We argue that, despite surface differences, these triads can all be reduced to similar underlying welfare trade-off ratios, which are a better candidate for social group primitives. Welfare trade-off ratios also have limitations, however, and we suggest there are multiple computational strategies by which people recognize and reason about social groups.

Heyes asks whether cultural learning mechanisms are cognitive instincts or cognitive gadgets. I argue that imitation does not fall into either category. Instead, its acquisition is promoted by its value in social interactions, which is evident across phylogeny and ontogeny and does not depend on the role of imitation in cultural learning.