What makes spinal-cord injuries as devastating as they are is that everything about them plays out in absolutes: they are instantaneous, utterly disabling and horribly permanent.

When it comes to raising civilized kids there are no hard rules, but there are two things on which most parents agree: Boys are generally wilder than girls, and adolescents are wilder than kids of any other age. If you've got an adolescent boy, you're in the sweet spot for trouble.

Indeed, the best way to think of willpower is not as some shapeless behavioral trait but as a sort of psychic muscle, one that can atrophy or grow stronger depending on how it's used.

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're learning how important it is both to preserve sibling relationships if they work and repair them if they're broken. We're also learning a lot about nonliteral siblings - stepsiblings, half-siblings - and the surprising power they can have.

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.