Human cognition is often biased, from judgments of the time of impact of approaching objects all the way through to estimations of social outcomes in the future. We propose these effects and a host of others may all be understood from an evolutionary psychological perspective. In this article, we elaborate error management theory (EMT;Haselton & Buss, 2000). EMT These two wisdoms seem contradictory. The first urges caution, whereas the second reminds us that we have nothing to lose and should throw caution to the wind. Yet both seem to capture aspects of human psychology. A person following both maxims would be a paranoid optimist, taking chances in some domains but simultaneously being fearful of certain kinds of harm. We argue, using insights from signal detection and error management theory (EMT), that there are good evolutionary reasons why the paranoid optimist mind could evolve. Furthermore, in which domains it is best to be paranoid and in which to be optimistic is predictable from the pattern of recurrent costs and benefits associated with decisions in that domain throughout our evolutionary history. This perspective suggests that one of the curiosities of human cognition-the fact that it seems riddled with biases-may be a functional feature of mechanisms for making judgments and decisions.Human cognition has often been shown to be biased. Perceivers underestimate the time-to-impact of approaching sounds (Neuhoff, 1998(Neuhoff, , 2001) and overestimate the connection between pictures of snakes and unpleasant outcomes such as electric shocks (Tomarken, Mineka, & Cook, 1989). People also appear to have a variety of positive illusions (Taylor & Brown, 1988), which cause them to overestimate the likelihood that they will succeed in spite of the adversity they face. Evidence in these domains and many others suggests that humans possess a multitude of biases, or propensities to adopt one belief on the basis of more slender evidence than would be required to believe in an alternative.Until recently, many psychologists have been content to describe these phenomena, their contexts of appearance, and possible implications, without much concern for their ultimate origin. As Krebs and Denton (1997) noted, in as much as explanation is needed, it tends to be proximate in nature. Psychologists argue that cognition is performed by a set of simple heuristic procedures, which are effective in many circumstances but prone to error in others (e.g., Kahneman, Slovic, & Tversky, 1982;Miller & Ross, 1975). Or, in social domains, biases in judgment serve the proximate function of preserving self-esteem or subjective happiness for the ego-centered human animal (Crocker & Park, 2003;Greenberg, Pyszczynski, Solomon, & Pinel, 1993;Kunda, 1990). Researchers offer evoked biases as examples of just such imperfections. Personality and Social Psychology Review 2006, Vol. 10, No. 1, 47-66 Copyright © 2006 by Lawrence Erlbaum Associates, Inc.
47We are grateful to Clark Barrett, Daniel Fessler, Mark Schaller and two reviewers for hel...