A Tale of Two Systems

In a Russian folktale, a scamp teaches a fool how to prepare a delicious soup that requires nothing but a soup stone. All one has to do is put the soup stone into boiling water. Yet, to achieve a better taste, it is desirable to add some vegetables, some meat to make the soup especially tasty, and some salt and pepper will do no harm, and so forth. A methodical examination of the development of two-system models during the past 10 years is reminiscent of the above folktale. Indeed, inspecting the different labels proposed and the various terminologies employed to characterize the presumed two systems and their corresponding alleged processes strongly suggest that it has become a stone soup where everything goes. Several authors (e.g., Gigerenzer & Reiger, 1996; Keren & Schul, 2009; Kruglanski & Gigerenzer, 2011; Osman, 2004) have critically assessed the viability and usefulness of the two-system approach. The recent expositions by Evans and Stanovich (2013, this issue, henceforth E&S) in this issue and elsewhere (e.g., Evans, 2009, 2011; Stanovich, 2009) suggest that they recognize many of the problems and seek to rectify them. Unfortunately, I suggest that their attempts are futile and, if anything, only increase confusion due to the addition of new theoretical constructs and the proposition that there may be more than two systems. My commentary has two different levels. At one level, I directly address E&S’s article, particularly commenting on what they now term a two-process theory. At a higher level, I consider E&S’s new model to be yet another version of what generically is referred to as “two-system” models and ask whether these indeed constitute theories or models as usually conceived by the scientific community. It is obviously beyond the scope of this article to provide an elaborated discussion of the nature of adequate scientific theories. Yet, it is commonly agreed that proper models should be based on well-defined constructs, motivate new questions, and yield testable predictions that will either corroborate or refute the theory under investigation. The central claim of this commentary is that none of the two-system theories, including the current version from E&S, satisfy the cardinal requirements of a scientific theory. Indeed, a previous article written in collaboration with my colleague Yaacov Schul (Keren & Schul, 2009) was meant to specify some (but certainly not all) basic requirements needed to transform two-system theories into testable ones. We realized that satisfying these requirements may be difficult, if not impossible, because these theories are so broad that they supposedly can account for almost all high-level social-cognitive phenomena. An important feature, in fact a necessary condition, for any scientific theory is a clear and unambiguous statement regarding the theory’s constraints and the corresponding boundaries. Otherwise, the theory becomes nothing but a set of arbitrary nominal definitions as the testable empirical world is not constrained. Inspection of two-system theories, including E&S’s version currently under discussion, unequivocally shows that the selective evidence they state to support their claims is, at best, consistent with the theoretical position rather than being based on direct tests derived from their theories. E&S’s article boils down to three main points: First, they agree with many of the criticisms of two-system models, yet believe that these were overstated. Second, they point out that most of the criticisms apply to a generic model, but they assert that the various models differ on different dimensions and thus should not be treated identically. Finally, they propose a new twoprocess theory that they believe is invulnerable to the common criticisms. In what follows, I briefly comment on each of these points. I close my commentary by raising two questions: First, I ask whether the current model, like its two-system predecessors, is testable in any scientific sense and probe whether the empirical evidence, brought by proponents of the theory, really supports their claims. Second, I question whether the ontological inquiry about the existence 483474 PPSXXX10.1177/1745691613483474KerenA Tale of Two Systems research-article2013