Academic journal article Memory & Cognition

Increased Sensitivity to Differentially Diagnostic Answers Using Familiar Materials: Implications for Confirmation Bias

Academic journal article Memory & Cognition

Increased Sensitivity to Differentially Diagnostic Answers Using Familiar Materials: Implications for Confirmation Bias

Article excerpt

Researchers have recently pointed out that neither biased testing nor biased evaluation of hypotheses necessitates confirmation bias-defined here as systematic overconfidence in a focal hypothesisbut certain testing/evaluation combinations do. One such combination is (1) a tendency to ask about features that are either very likely or very unlikely under the focal hypothesis (extremity bias) and (2) a tendency to treat confirming and disconfirming answers as more similar in terms of their diagnosticity (or informativeness) than they really are. However, in previous research showing the second tendency, materials that are highly abstract and unfamiliar have been used. Two experiments demonstrated that using familiar materials led participants to distinguish much better between the differential diagnosticity of confirming and disconfirming answers. The conditions under which confirmation bias is a serious concern might be quite limited.

Although a wide variety of reasoning and decisionmaking errors have been reported (e.g., Evans, Newstead, & Byrne, 1993; Gilovich, Griffin, & Kahneman, 2002; Kahneman & Tversky, 2000), they are often disputed. For example, it has been argued that participants often construe tasks differently than do experimenters (Hilton, 1995; Schwarz, 1996), that some purported errors are consistent with an alternative normative standard (Anderson, 1990, 1991; Chase, Hertwig, & Gigerenzer, 1998; Gigerenzer, 1991, 1996; Gigerenzer, Todd, and the ABC Research Group, 1999; McKenzie, 2004a; McKenzie & Mikkelsen, in press; Oaksford & Chater, 1994, 1996, 2003; Sher & McKenzie, in press), and that many errors are limited to (or at least exacerbated by) the laboratory environment (Anderson, 1990, 1991; Klayman & Ha, 1987; McKenzie, 2003,2004b; McKenzie & Mikkelsen, 2000; McKenzie & Nelson, 2003; Oaksford & Chater, 1994,1996,2003). This article takes the latter position on confirmation bias-one of the most widely cited errors in the reasoning literatureand argues that the conditions under which the bias occurs are more limited than previously thought.

Confirmation bias is usually said to occur in tasks that fall under the topic of hypothesis development (Klayman, 1995), which is concerned with how people put their ideas or hypotheses to test. For present purposes, this process will be seen in terms of three components: hypothesis generation, testing, and evaluation. In the context of a physician's diagnosing a patient, hypothesis generation occurs when the physician produces possible causes of the patient's symptoms. The testing component refers to the physician's deciding which questions to ask the patient or which tests to run in order to help determine whether a generated hypothesis is correct. Once answers or test results are known, the evaluation component occurs: How strongly do the results support or refute the hypothesis?

Hypothesis development is not limited to relatively formal settings, such as ones in which physicians diagnose illnesses or scientists test theories. People constantly engage in hypothesis development as a means of imposing structure on complex environments (Brehmer, 1980; McKenzie, 2004b). Given the importance of hypothesis development, it is not surprising that it has been the focus of much psychological research over the past several decades (for reviews, see Klayman, 1995; McKenzie, 2004b; Poletiek, 2001). However, widespread interest in the topic did not develop until Wason's (1960) article, which cast lay hypothesis development in a bad light. People were said to be prone to confirmation bias because they appeared to be trying to confirm the hypothesis that they were entertaining.

As has been noted by Fischhoff and Beyth-Marom (1983; see also Klayman, 1995; Klayman & Ha, 1987), confirmation bias has been used to describe many different phenomena. In this article, the bias will be said to occur if people behave in a way that leads to systematic overconfidence in a focal hypothesis (i. …

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