The origins of bubbles in laboratory asset markets

In twelve sessions conducted in a typical bubble-generating experimental environment, we design a pair of assets that can detect both irrationality and speculative behavior. The specific form of irrationality we investigate is probability judgment error associated with low-probability, high-payoff outcomes. Independently, we test for speculation by comparing prices of identically paying assets in multiperiod versus single-period markets. When these tests indicate the presence of probability judgment error and speculation, bubbles are more likely to occur. This finding suggests that both factors are important bubble drivers.