The theory-based model of categorization posits that concepts are represented as theories rather than as feature lists. Thus, it is particularly interesting that the DSM-IV (American Psychiatric Association, 1994), establishes a set of atheoretical guidelines for diagnosis in the domain of mental disorders. Five experiments investigated how clinicians handle an atheoretical nosology. Clinical psychologists' causal theories for DSM-IV disorders and their responses on diagnostic and memory tasks were measured. Participants were more likely to diagnose a hypothetical patient with a disorder if that patient had causally central rather than causally peripheral symptoms according to their theory of the disorder. They also showed biased memory for the causally central symptoms. Clinicians are cognitively driven to form and apply theories despite decades of training and practice with the DSM's atheoretical guidelines. Clinical Psychologists' Theory-Based Representations of Mental Disorders Predict their Diagnostic Reasoning and Memory The theory-based view of categorization proposes that concepts are represented as theories or causal explanations. Murphy and Medin (1985) suggested that our nave theories about the world hold the features of a concept together in a cohesive package. For instance, a layperson's concept of anorexia not only contains the features "fear of becoming fat" and "refuses to maintain minimal body weight," but also the notion that the fear of becoming fat helps cause the refusal to maintain minimal body weight (Kim & Ahn, 2002). Indeed, a growing body of evidence supports the notion that the human mind constantly seeks out rules and explanations that make sense of incoming data concerning its surroundings, and forms concepts based on its theories about the ...

Abstract. Th is study addresses the counselling of heterosexual men with low-risk behaviour who, voluntarily or involuntarily, take a HIV test. If such a man tests positive, the chance that he is infected can be as low as 50%. We study what information counsellors communicate to clients concerning the meaning of a positive test and whether they communicate this information in a way the client can understand. To get realistic data, one of us visited as a client 20 public health centres in Germany to take 20 counselling sessions and HIV tests. A majority of the counsellors explained that false positives do not occur, and half of the counsellors told the client that if he tests positive, it is 100 % certain that he is infected with the virus. Counsellors communicated numerical information in terms of probabilities rather than absolute frequencies, became confused, and were inconsistent. Based on experimental evidence, we propose a simple method that counsellors can learn to communicte risks in a more eff ective way. Former Senator Lawton Chiles of Florida reported at an AIDS conference in 1987 that of 22 blood donors in Florida who were notifi ed that they tested HIV-positive with the ELISA test, seven committed suicide. In the same medical text that reported this tragedy, the reader is informed that “even if the results of both AIDS tests, the ELISA and WB (Western blot), are positive, the chances are only 50–50 that the individual is infected ” (Stine, 1996, pp. 333, 338).

this article unless noted otherwise). The names of ss'mptoms are abbreviated because of space limitations (full names of the criterial symptoms can be fbund in Table 1). The symptoms circled with double lines are criterial symptoms, and those circled with single lines are characteristic symptoms. One interesting result to notice is that even among criterial symptoms, causal centrality (as grossly indicated by the number of symptoms that a symptom causes and their strengths) seems highly variable. For instance, on average, participants believe that in anorexia nervosa, "fear of being fat even when underweight" causes many symptoms, including fear of eating in public, bingeing and purging, excessive dieting, and refusal to gain weight. However, "absence of the period (in women) for 3+ menstrual cycles," another criterial symptom for anorexia nervosa, was rarely judged to cause any other symptoms of that disorder. Figure 1 suggests that a conceptually central symptom (e.g., "fear of being fat even when underweight" in anorexia nervosa) is also causally central, and a conceptually peripheral symptom (e.g., "absence of the period (in women) tbr 3+ menstrual cycles") is also cansally peripheral. This would be consistent with our primary hypothesis that a symptom is conceptually central to the extent that it causes other features. However, it is also apparent from Figure 1 that not all such pairwise comparisons, as in all of psychological research, were perfect one-to-one correspondences. Therefore, we tested for statistical significance as follows

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