The smartest groups, then, are made up of people with diverse perspectives who are able to stay independent of each other.

Lower oil prices won't, by themselves, topple the mullahs in Iran. But it's significant that, historically, when oil prices have been low, Iranian reformers have been ascendant and radicals relatively subdued, and vice versa when prices have been high.

Technological innovation has dramatically lowered the cost of computing, making it possible for large numbers of consumers to own powerful new technologies at reasonably low prices.

If you work for Google or Apple, stock options give you a chance to share in the increasing value of the company. In the N.F.L., nothing like this happens; the players, though rich, are just working stiffs like the rest of us.

Behavioral economists have shown that a sizable percentage of people are willing to pay real money to punish people who are taking from a common pot but not contributing to it. Just to insure that shirkers get what they deserve, we are prepared to make ourselves poorer.

In conditions of uncertainty, humans, like other animals, herd together for protection.

Procrastination also can be a way of self-handicapping: if you don't do a great job, you can always say to yourself, "If I'd only started sooner, I'd have been able to produce something excellent."