The financial crisis of 2008 was not caused by investment banks betting against the housing market in 2007. It was caused by the fact that too few investors - including all of the big investment banks - bet too heavily on the housing market in the years before 2007.

The world's central banks and the International Monetary Fund still have vaults full of bullion, even though currencies are no longer backed by gold. Governments hold on to it as a kind of magic symbol, a way of reassuring people that their money is real.

The important thing about groupthink is that it works not so much by censoring dissent as by making dissent seem somehow improbable.

If army ants are wandering around and they get lost, they start to follow a simple rule:Just do what the ant in front of you does. The ants eventually end up in a circle. There's this famous example of one that was 1,200 feet long and lasted for two days; the ants just kept marching around and around in a circle until they died.

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."

Of course, presidents are always blamed or rewarded for the state of the economy.

Pop music thrives on repetition. You know a song's a hit when you've heard it so often that you'll be happy never to hear it again.