Meir Statman told Wall Street Journal columnist Jason Zweig (The Intelligent Investor) that "investment value" -- that is, the measure of a stock's worth now and in the future -- is often overcome by hope (in a rising market) and regret (in a declining market). "The evidence does suggest that the market is not rational," he said. But he cautioned that investors, for the most part, can't out-reason markets. Read the column here >> 1/9/10