Understanding the minds of nonhuman animals promises to shed light on the origins of such cognitive abilities as, in this case, knowing and analyzing the contents of one’s own brain. That’s how people solve challenges and make discoveries — what do I know? what if I look at it this way? — and it’s a pillar of higher intelligence. Knowing what you know is also a form of consciousness, and the discovery that more and more nonhumans seem to have it raises tricky questions about how we treat them.