There are a lot of ways to make people not like you, but one of the most powerful - if least fair - is to be really, really successful. Nobody resents the guy who just lost his job. But the guy whose Internet start-up made him a billionaire at 25? That's a whole different kettle of envy.

There's no such thing as downtime for your brain.

Well, I think of the folks who are the climate deniers as the flat Earthers and the people who say the moon landings never happened.

Introverts listen better, they assess risks more carefully, they can be wiser managers. It's not for nothing that the Silicon Valley billionaires are so often the retiring types.

Certainly, people can get along without siblings. Single children do, and there are people who have irreparably estranged relationships with their siblings who live full and satisfying lives, but to have siblings and not make the most of that resource is squandering one of the greatest interpersonal resources you'll ever have.

Older siblings get more total-immersion mentoring with their parents before younger siblings come along. As a result, they get an IQ and linguistic advantage because they are the exclusive focus of their parents' attention.

The brain sits snugly inside the skull, but it's not a completely flush fit - there is still a layer of fluid between bone and soft tissue that serves as a natural shock absorber. Some shocks, however, can't be absorbed, and when the head gets clobbered too hard, the brain can twist or torque or rattle around inside its skeletal casing.