I’ve been thinking deeply about this over the last couple of weeks. So sure, the obvious answer is the overriding human reward function is survival, propagation of our dna. Except I think it’s more complex than that, take War for example where people sacrifice themselves for an idea of nationality or culture, that goes against the ‘selfish gene’ theory. I think the answer is there are multiple reward functions that compete for dominance. Perhaps each of the different ‘brains’ has it’s own reward function.