1. CP as a straw man

First, they cast CP as a theory of the mind. For Ward Edwards, the founder of research on behavioral decision making and the first to use the term “subjective probability,” as well as for Kahneman & Tversky and their adherents, CP served as a point of comparison. Although one might argue that sensible decisions ought to follow CP, judgment and decision making (JDM) research has largely been about how decisions made by people do not. To use Baron's (Reference Baron, Koehler and Harvey2004) terminology, CP may be useful as a prescriptive theory of behavior, but not as a descriptive theory.

The appeal of CP to most psychologists is quite different. We seek a way to describe uncertainty. Uncertainty is a central construct that all sciences need to address. If there is to be any hope of communicating across disciplines (or subfields of psychology), we need to use that common construct.

2. Distorting behavior to accommodate mathematical requirements

Second, in order to define probabilities, P&B readily dichotomize a continuum. For example, they discuss two questions: (1) Is the person happy? (2) Is the person employed? They treat these questions as if they are equivalent, both having yes-no answers, and assign probabilities to the responses. The focus is on how the answers interplay: happiness might be more probable if a person is employed (because he or she has money) or less probable (because she hates her job).

However, happiness is a continuum, not a dichotomy. Translating from mathematical exercises into real research questions allows this distinction to be seen clearly. For example, one might try a manipulation to change a person's degree of happiness. The change could be measured, perhaps, by asking, “How happy are you now?” at various times. The amount of change, as opposed to whether there has been a change of status, is important.

Dichotomizing not only loses information (MacCallum et al. Reference MacCallum, Zhang, Preacher and Rucker2002), it can seriously distort substantive inferences. The latter danger is illustrated in the critique of a respected index of clinically significant change (Jacobson et al. Reference Jacobson, Roberts, Berns and McGlinchey1999) by Weiss et al. (Reference Weiss, Edwards, Weiss, Weiss and Weiss2009). In contrast, employment has only two, or maybe a few (part-time, or multiple-jobs) states. Therefore, it makes sense to use dichotomized responses in asking a subject about employment (“did the manipulation change your employment status?”).

3. Complexity beyond the needs of the research domain

Third, although the level of mathematical sophistication underlying QP is admirable, we view it as a case of overkill. As argued by fourteenth century logician and Franciscan friar William of Ockham, “entities should not be multiplied unnecessarily.” This recommendation is now commonly known as “Occam's Razor.” Ultimately, of course, whether complexity is excessive is a subjective matter. It is our opinion that P&B have developed an unnecessarily complicated alternative to CP.

Traditional CP is notable for its simplicity. Augmented with a Bayesian perspective, it has been a remarkably valuable tool for stimulating JDM researchers ranging from Edwards in the 1950s and 1960s, to Kahneman and Tversky in the 1970s and 1980s, to Gigerenzer and colleagues in the 1990s and 2000s, to the recent Behavioral & Brain Sciences article by Elqayam and Evans (Reference Elqayam and Evans2011) arguing for a distinction between normative systems and competence theories (see Brase & Shanteau Reference Brase and Shanteau2011).

Young (Reference Young1996) explained to the Psychometric Society why he was no longer interested in building increasingly more sophisticated algorithms for multi-dimensional scaling (MDS). Young had been one of the pioneers in developing MDS tools. His arguments can be summarized by the following quotes from his presentation: “Application to problems in Psychology and Social Sciences have gotten lost in the process of developing more complex methods and models… The methods and models have gotten much more complicated than users can understand…We are too focused on mathematics at the expense of usefulness.” We believe that Young's comments on MDS are equally applicable to the article by P&B.

4. Physics Envy

There has been ongoing discussion among behavioral scientists regarding “Physics Envy” (Mirowski Reference Mirowski1992; Sapolsky Reference Sapolsky1997; Schabas Reference Schabas and de Marchi1993). In part, recent discussions in economics (Lo & Mueller Reference Lo and Mueller2010) have been motivated by the role of so-called “quants” in the 2007 financial meltdown. As Malkiel noted, whereas “physical models can provide an accurate description of reality…financial models, despite their mathematical sophistication, can at best provide a vast oversimplification of reality” (Malkiel Reference Malkiel2011, p. 1)

Although we are not as pessimistic about the role of mathematical models in psychology, we share the concern about using physics as a standard against which to evaluate theories in psychology. The issue, according to Lo and Mueller, is that “human behavior is not nearly as stable as and predictable as physical phenomena” (Lo & Mueller Reference Lo and Mueller2010, p. 13). Therefore, tools appropriate for advances in physics may not be nearly as useful in psychology.