Simultaneous Contradictory Belief and the Two-Systems Hypothesis

Simultaneous Contradictory Belief and the Two-System Hypothesis Joshua Mugg (joshuamugg@gmail.com) Department of Philosophy, 4700 Keele St. Toronto, ON M3J 1P3 Canada criticism of the two-system hypothesis has focused on the kind claim (Samuels 2009; Evans 2011), I argue that Sloman has not provided us with cases of SCB. I then offer an experimental setup that would strongly support the existence of SBC. Abstract The two-system hypothesis states that there are two kinds of reasoning systems, the first of which is evolutionarily old, heuristically (or associatively) based, automatic, fast, and is a collection of independent systems. The second is evolutionarily new, perhaps peculiar to humans, is rule-based, controlled, slow, and is a single token system. Advocates of the two-system hypothesis generally support their claim by an inference to the best explanation: two systems are needed to explain experimental data from the reasoning, heuristics, and biases literature. The best evidence for this claim comes from simultaneous contradictory belief (henceforth SCB) (Sloman 1996, 2002). I argue that Sloman has not provided us with cases of SCB. In each of his examples there is no evidence that the beliefs are held simultaneously. I then offer the outline for an experimental setup that would offer compelling evidence for the existence of SCB and thereby support the two-system hypothesis. Keywords: Dual-process; two-system simultaneous contradictory belief. Why SCB? hypothesis; Introduction The two-system hypothesis states there are two reasoning systems (or at least two kinds of reasoning systems), the first of which (System 1 or ‘S1’) is evolutionarily old, heuristically (or associatively) based, automatic, fast, and is a collection of independent systems. The second (System 2 or ‘S2’) is evolutionarily new, perhaps peculiar to humans, is rule-based, controlled, and slow. 1 The advocate of the two-system hypothesis must demonstrate that the two systems are distinct (what I call the distinctness claim), that the two systems are of different kinds (what I call the kind claim), and that S2 is a single system. Advocates of the two- system hypothesis (I have in mind Evans (2004); Evans & Over (1996); Sloman (1993, 1996); Stanovich (1999, 2004); Carruthers (2009); and Frankish (2004, 2009)) generally support their claim by an inference to the best explanation: two systems are needed to explain experimental data from the reasoning, heuristics, and biases literature. The best evidence for this claim comes from simultaneous contradictory belief (henceforth SCB) (Sloman 1996, 2002). However, their inference to the best explanation only supports, if successful, the distinctness claim. While For a complete list of the property clusters of S1 and S2, sometimes called the ‘Standard Menu’, see Evans and Frankish (2009). I take the two-system hypothesis to be stronger than the existential claim that there are two systems of reasoning. The thesis is that cognition is divided into two systems and that each system has a certain set of properties associated with it—the properties on the Standard Menu. Before examining Sloman’s cases of SCB we need to understand why SCB is good evidence for the two-system hypothesis, and we need to understand what counts as evidence for SCB. Sloman seems to have a rival explanation in mind to account for human reasoning: there is just one reasoning system (call this the one-system hypothesis). The one-system hypothesis can and should allow that this system operates differently under different circumstances. It should, for example, sometimes operate deductively and other times inductively. The two-system theorist allows for a single system to operate inductively and deductive on different occasions, since S1 and S2 engage in both forms of reasoning. What, we should ask, would be the empirical difference between there being one reasoning system that operates differently under different stimuli and there being multiple systems? One reasoning system cannot have contradictory outputs for one input (Here I am in agreement with Sloman (1996, 2002)). So the one-system hypothesis is committed to the following claim: for any question demanding reasoning and for which a reasoning system will produce only one answer, subjects will only offer one answer at any given time. Sloman understands ‘belief’ broadly to mean “a propensity, feeling, or conviction that a response is appropriate even if it is not strong enough to be acted on” (384). This definition is not uncontroversial, but (for the sake of argument) I will grant it for the purpose of this paper. From Sloman’s definition it follows that there are at least two ways in which subjects might offer more than one response at any given time. The first is behavioral. While people might explicitly say that they believe that p, they may exhibit behavior demonstrating that they believe not-p. This would be evidence that there is more than one system involved in reasoning. They believe (explicitly) that p but believe (dispositionally, tacitly, or implicitly) not-p. Second, a subject might feel a tension between p and not-p. This is phenomenological evidence for SCB. As an example of a task where subjects give simultaneous contradictory responses which indicates the existence of distinct systems, consider the Muller-Lyer illusion. Subjects believe that the two lines are equal, but cannot help but see them as different lengths, even after they have measured the