Individual Differences in Rational Thinking Time

Individual Differences in Rational Thinking Time Wim De Neys (Wim.Deneys@psy.kuleuven.be) Kristien Dieussaert (Kristien.Dieussaert@psy.kuleuven.be) Department of Psychology, K.U. Leuven, Tiensestraat 102 B-3000 Leuven, Belgium automatically whereas the operations of the analytic system would be slow and heavily demanding of our limited working memory resources. Both systems have been shown to reside in different brain regions (Goel & Dolan, 2003). It is assumed that in most situations the heuristic and analytic system interact in concert. Hence, most of the time the heuristic default system will provide us with fast, frugal, and correct conclusions. However, the prepotent heuristics may also bias reasoning in situations that require more elaborate, analytic processing. That is, both systems will sometimes conflict and cue different responses. In these cases the analytic system will need to override the belief-based response generated by the heuristic system (Stanovich & West, 2000). The inhibition of the heuristic system and the computations of the analytic system would draw on limited, executive working memory resources. Therefore, correct analytic reasoning in case of a belief-logic conflict would be characteristic of those highest in working memory span: The more resources that are available, the more likely that the analytic system will be successfully engaged and the correct response calculated. Individual difference studies on the belief bias effect in syllogistic reasoning provide paradigmatic support for the framework. Belief bias refers to the heuristic tendency to judge the validity of a syllogism by evaluating the believability of the conclusion (e.g., Klauer, Musch, & Naumer, 2000; Oakhill, Johnson-Laird, & Garnham, 1989; Newstead, Pollard, Evans, & Allen, 1992). For some syllogistic problems the logical status of the conclusion conflicts with background beliefs (i.e., conflict items, see Appendix for examples). The heuristic, belief-based system thus triggers an erroneous response and consequently many people fail to solve these problems correctly. For other syllogisms the logical status of the conclusion is consistent with the believability of the conclusion (i.e., no-conflict items). Correct solution rates on these no-conflict items are uniformly high. Consistent with the dual process framework it has been observed (e.g., Kokis et al., 2002; Newstead et al., 2004; Stanovich & West, 1999, 2000) that individual differences in cognitive capacity predict performance on the conflict items but not on the no-conflict items. Indeed, the heuristic system is assumed to operate automatically, that is, it should not burden the limited executive resources. Hence, when the heuristic-belief based response is consistent with the logical response even the heuristically reasoning low spans will get the Abstract Individual difference studies suggest that reasoners highest in cognitive capacity favor analytic, normative responses over fallacious, heuristic responses. The present study complemented reasoning accuracy with timing data to obtain an indication of the nature of the reasoning process underlying the response selection. A total of 199 participants were presented with a measure of working memory capacity and a syllogistic reasoning task. As predicted, higher spans were not only more likely to draw a correct conclusion but also reasoned longer when believability and logical status of the conclusion conflicted. Working memory capacity did not predict reasoning accuracy or time when believability and logic were consistent. Findings validate basic processing assumptions of a dual process framework of thinking. Introduction In recent years, studies on individual differences in reasoning performance moved to the center stage of the cognitive research on human thinking. Over the last decades an impressive body of research established that human reasoning frequently violates normative standards: In a wide range of reasoning tasks the majority of educated adults fails to give the response that is correct according to logic or probability theory (Evans, 2002; Kahneman, Slovic, & Tversky, 1982). The exact nature and consequences of this “rational thinking failure” instigated a rife debate (e.g., Stein, 1996). Systematic research on individual differences in cognitive capacity (e.g., Kokis, Macpherson, Toplak, West, & Stanovich, 2002; Klaczynski, 2001; Newstead, Handley, Harley, Wright, Farrelly, 2004; Stanovich & West, 1999, 2000; Torrens, Thompson, & Cramer, 1999) pointed to the crucial stipulation that participants highest in cognitive (working memory) capacity do manage to solve the problems correctly. According to influential dual process theories of thinking, correct normative responding in classic reasoning tasks requires that an analytic, controlled reasoning process overrides prepotent heuristics (e.g., Epstein, 1994; Evans, 2003; Evans & Over, 1996; Sloman, 1996; Stanovich & West, 2000). Advocates of the dual process framework have distinguished two types of reasoning systems. In general, the first, so-called heuristic system is characterized by a tendency towards an automatic contextualization of a problem with prior knowledge and beliefs whereas the second, so-called analytic system tends to decontextualize a problem and allows reasoning according to normative standards. The heuristic default system is assumed to operate fast and