The mind of the polyglot is a very particular thing, and scientists are only beginning to look closely at how acquiring a second language influences learning, behavior and the very structure of the brain itself.

We are all born with an innate understanding of interpersonal equity - the idea that if you lend me your rake today, I'll respond in kind when you come to borrow my shovel tomorrow. Or nearly all of us are born with that. Psychopaths aren't.

There are a lot of obstacles in the way of our understanding animal intelligence - not the least being that we can't even agree whether nonhuman species are conscious. We accept that chimps and dolphins experience awareness; we like to think dogs and cats do. But what about mice and newts? What about a fly? Is anything going on there at all?

When we're awake, cortisol can fragment memories - one reason eyewitness crime scene accounts are so unreliable. But at night that very fragmentation allows creative recombinations of ideas.