How great investors can do better revealed

Researchers at Caltech and Virginia Tech that looked at the brain activity and behavior of people trading in experimental markets where price bubbles formed. In such markets, where price far outpaces actual value, it appears that wise traders receive an early warning signal from their brains-a warning that makes them feel uncomfortable and urges them to sell, sell, sell.

Colin Camerer, the Robert Kirby Professor of Behavioral Economics at Caltech, said that seeing what's going on in people's brains when they are trading suggests that Buffet was right on target.

Camerer and his colleagues found two distinct types of activity in the brains of participants-one that made a small fraction of participants nervous and prompted them to sell their experimental shares even as prices were on the rise, and another that was much more common and made traders behave in a greedy way, buying aggressively during the bubble and even after the peak.

The researchers set up a simple experimental market in which they were able to control the fundamental, or actual, value of a traded risky asset. In each of 16 sessions, about 20 participants were told how an on-screen trading market worked and were given 100 units of experimental currency and six shares of the risky asset. Then, over the course of 50 trading periods, the traders indicated by pressing keyboard buttons whether they wanted to buy, sell, or hold shares at various prices.

The study found that the low earners tended to be momentum buyers who started buying as prices went up and then kept buying even as prices tanked. The middle-of-the-road folks didn't take many risks at all and, as a result, neither made nor lost the most money. And the traders who earned the most bought early and sold when prices were on the rise.

The study was published in the Proceedings of the National Academy of Sciences.