| Abstract: | We compare two competing theories of financial anomalies: "behavioral"theories built on investor irrationality, and "rational structuraluncertainty" theories built on incomplete information aboutthe structure of the economic environment. We find that althoughthe theories relax opposite assumptions of the rational expectationsideal, their mathematical and predictive similarities make themdifficult to distinguish. Even if irrationality generates financialanomalies, their disappearance still may hinge on rational learning—thatis, on the ability of rational arbitrageurs and their investorsto reject competing rational explanations for observed pricepatterns. |
