Why are bubbles such a persistent feature of financial history? Economists argue that these speculative frenzies are caused in part by market failures like too much liquidity or lax regulation. Cognitive psychologists, meanwhile, see bubbles as a case of pattern recognition gone awry, as people extrapolate the past into the future. In recent years, neuroscientists also have become interested in bubbles, if only because the financial manias seem to take advantage of deep-seated human flaws; the market fails only because the brain fails first. Read Montague, at Baylor College of Medicine, has spent the last few years trying to decipher the bits of brain behind our irrational exuberance. It’s microeconomics at its most microscopic.