Rule-Based Reasoning Is Fast and Belief-Based Reasoning Can Be Slow: Challenging Current Explanations of Belief-Bias and Base-Rate Neglect

It is commonly assumed that belief-based reasoning is fast and automatic, whereas rule-based reasoning is slower and more effortful. Dual-Process theories of reasoning rely on this speed-asymmetry explanation to account for a number of reasoning phenomena, such as base-rate neglect and belief-bias. The goal of the current study was to test this hypothesis about the relative speed of belief-based and rule-based processes. Participants solved base-rate problems (Experiment 1) and conditional inferences (Experiment 2) under a challenging deadline; they then gave a second response in free time. We found that fast responses were informed by rules of probability and logical validity, and that slow responses incorporated belief-based information. Implications for Dual-Process theories and future research options for dissociating Type I and Type II processes are discussed.