In this paper, I provide a qualified defense of the claim that cognitive biases are not necessarily signs of irrationality, but rather the result of using normative standards that are too narrow. I show that under certain circumstances, behavior that violates traditional norms of rationality can be adaptive. Yet, I express some reservations about the claim that we should replace our traditional normative standards. Furthermore, I throw doubt on the claim that the replacement of normative standards would license optimistic verdicts (...) about human rationality. (shrink)