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This was the year when the reckless behavior of risk takers from Wall Street traders to mortgage lenders to Bernie Madoff blew up in everyone's faces. So it will probably come as cold comfort to learn why certain people are willing to commit such daring acts: It's because they have fewer inhibitors of happy-chemical dopamine in their brains, neuroscience researchers have discovered. So they get an extra feel-good high whenever they take a risk, predisposing them to keep flirting with danger—until, you know, the market crashes or the feds come knocking.