Abstract

In lieu of an abstract, here is a brief excerpt of the content:Anorexia and the MacCAT-T Test for Mental Competence:Validity, Value, and EmotionLouis C. Charland (bio)Keywordsmental competence, decisional capacity, anorexia, value, emotionValidity of the MacCAT-THow does one scientifically verify a psychometric instrument designed to assess the mental competence of medical patients who are asked to consent to medical treatment? Aside from satisfying technical requirements like statistical reliability, results yielded by such a test must conform to at least some accepted pretheoretical desiderata; for example, determinations of competence, as measured by the test, must capture a minimal core of accepted basic intuitions about what competence means and what a theory of competence is supposed to do. The concepts of "face validity" and "content validity" are both important here. Face validity "indicates that an instrument appears to test what it is supposed to and that it is a plausible method for doing so" (Portney and Watkins 2000, 82). Content validity "means that the test contains all the elements that reflect the variable being studied" (Portney and Watkins 2000, 83). An adequate instrument for measuring mental competence must at minimum satisfy both of these requirements.What Tan and her colleagues (2006) have shown is that the MacArthur Competence Assessment Tool—Treatment (MacCAT-T) test for mental competence may not be an empirically valid measure of mental competence for some cases of anorexia. The data they report show that "competence," as measured by the MacCAT-T, does not conform sufficiently well with what is wanted of a clinical medical theory of competence. More specifically, the MacCAT-T is deficient in both face and content validity. This result is extremely significant; previous challenges to the validity of the MacCAT-T have often been largely theoretical in nature. My own objection that the MacCAT is inadequate because it omits the influence of emotion is based on a combination of empirical theory (Charland 1998a) and philosophical argument (Charland 1998b). However, it is entirely theoretical in nature. So is my argument that in ignoring emotion the MacCAT misses a crucial contributing ingredient in competence, namely, value (Charland 2001, see especially 136 note 2). Tan's study provides valuable empirical evidence for the second of these challenges, which deals more specifically with value. On the one hand, the study clearly demonstrates that patients sometimes do [End Page 283] base their treatment decisions on reasons derived from values. And on the other hand, it also nicely illustrates the centrality of values—"utilities" or "preferences"—in the decision-making process generally; a basic assumption of standard decision theory for which, paradoxically, there appears to be no satisfactory counterpart in the MacCAT-T model of reasoning and decision making.Thus, values figure among the reasons that patients actually use in reasoning when they weigh the risks and benefits of proposed treatment options. The MacCAT-T must be amended to incorporate this fact if it is to be a satisfactory clinical medical tool. Without such a correction, the concept of mental competence it measures is empirically invalid. At the root of the problem is a clash of intuitions. Tan's data provide convincing evidence that some of the patients who are deemed to be mentally competent by MacCAT-T standards should not in fact be considered competent. Note that the language in which this clash is expressed—"should not in fact"—involves a combination of descriptive and prescriptive elements, reminding us that the concept of competence is dual in nature: it is both prescriptive and descriptive (Freedman 1981). These problems underscore the need for greater clarity about what pretheoretically we want a clinical theory and test of competence to capture. It is of course reasonable to say that such a test must be consistent with major tenets of the relevant case law (Appelbaum 1998). But a legally valid concept of competence of this sort is too thin and arbitrary a foundation on which to build a clinical medical theory of competence. An empirically valid theory and test of the latter sort must incorporate the role of values if it is be truly helpful in medical practice.Value and the MacCAT-TI agree with Tan and her colleagues that some notion of "pathological value" needs to be...