Patricia S. Churchland at Edge:
The question that I’ve been perplexed by for a long time has to do with moral motivation. Where does it come from? Is moral motivation unique to the human animal or are there others? It’s clear at this point that moral motivation is part of what we are genetically equipped with, and that we share this with mammals, in general, and birds. In the case of humans, our moral behavior is more complex, which is probably because we have bigger brains. We have more neurons than, say, a chimpanzee, a mouse, or a rat, but we have all the same structures. There is no special structure for morality tucked in there.
Part of what we want to know has to do with the nature of the wiring that supports moral motivation. We know a little bit about it, namely that it involves important neurochemicals like oxytocin and vasopressin. It also involves the hormones that have to do with pleasure, endocannabinoids and the endogenous opioids. That’s an important part of the story. The details are by and large missing. And what I would love to know, of course, is much more about the details.