How do investors perceive dependence between stock returns; and how does their perception of dependence affect investments and stock prices? We show experimentally that investors understand differences in dependence, but not in terms of correlation. Participants invest as if applying a simple counting heuristic for the frequency of comovement. They diversify more when the frequency of comovement is lower even if correlation is higher due to dependence in the tails. Building on our experimental findings, we empirically analyze U.S. stock returns. We identify a robust return premium for stocks with high frequencies of comovement with the market return.

Prices and returns are alternative ways to present information and to elicit expectations in financial markets. But do investors think of prices and returns in the same way? We present three studies in which subjects differ in the level of expertise, amount of information, and type of incentive scheme. The results are consistent across all studies: asking subjects to forecast returns as opposed to prices results in higher expectations, whereas showing them return charts rather than price charts results in lower expectations. Experience is not a useful remedy but cognitive reflection mitigates the impact of format changes.