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claim that the earth was not the center of the solar system, put him under house arrest for the last eight years of his life? In part, the answer lies in the distinction between skepticism and closed-mindedness. Many scientists who were skeptical about cold fusion nevertheless tried to replicate the reported phenomenon in their own labs; Galileo’s critics refused to look at the pertinent data. Equally important, however, is the foundation on which a person’s pre-existing beliefs and theories rest. We are justified in allowing our beliefs and theories to influence our assessments of new information in direct proportion to how plausible and well-substantiated they are in the first place. One need not feel concerned about quickly dismissing a purported levitation because our faith in the inexorable effect of gravity has been built up by a lifetime of consistent experience. Well-supported beliefs and theories have earned a bit of inertia, and should not be easily modified or abandoned because of isolated antagonistic “facts.” In marked contrast, many ethnic, gender, and occupational stereotypes are particularly troublesome because they often rest on such flimsy or non-existent evidence to begin with.
    All of this is to say that the question of how even-handed we should be in evaluating evidence is rather complex. Not all bias is a bad thing; indeed, a certain amount is absolutely essential. The power and flexibility with which we reason depends upon our ability to use context, generic knowledge, and pre-existing information to disambiguate and extract meaning from new information—and, to some degree, to bias our interpretation of evidence. Consider, for example, the newspaper headline, “Mondale’s offensive looks hard to beat.” 2 Nothing in the words themselves allows us to determine whether it is referring to Mondale’s campaign strategy or to his physical appearance. Nevertheless, our pre-existing knowledge of what is and is not plausible allows us to quickly and effortlessly draw the correct conclusion.
    Note, however, that it has proven extremely difficult to program even the most advanced computers to make such “simple” inferences. 3 3 Thus, without this ability to use context and expectations to “go beyond the information given,” 4 we would be unintelligent in the same way that computers with superior compututional capacity are unintelligent. As dysfunctional as they may be on occasion, our theories, preconceptions, and “biases” are what make us smart.
THE PATH OF BIAS
     
    Ambiguous Information. Our expectations can bias our evaluation of new information in two ways, depending largely on whether or not the information is ambiguous. Truly ambiguous information is often simply perceived in a way that fits our preconceptions. Consider how the stimulus “13” is differently perceived in the context of “12, 13, 14” versus “A, 13, C.” Similarly, the same smile can look warm and friendly when it is worn by someone we like, but smug or sinister when worn by someone we consider untrustworthy.
    A particularly interesting example of how our expectations can influence what we see involves people’s negative associations to the color black and how they can influence the perceived aggressiveness of someone wearing black clothing. The “bad guys” have worn black hats since the invention of motion pictures, and psychological research has shown that film directors who employ this tactic are capitalizing on a very basic psychological phenomenon: Surveys conducted in a wide range of cultures reveal that black is seen as the color of evil and death in virtually all corners of the world.
    This negative association leads to several interesting results in the domain of professional sports. When my colleague Mark Frank and I asked a group of respondents to rate the appearance of professional football and hockey uniforms, they judged those that were at least half black to be the most “bad,” “mean,”