Critical thinking classes can reduce common biases: Results from a field experiment

Critical thinking classes are ubiquitous in U.S. college curricula. One of their aims is to teach good reasoning skills. To date, there is little systematic evidence that they do this. We report the results of a field experiment (N = 397) that compared undergraduate critical thinking classes taught in a philosophy department to other undergraduate philosophy classes. The results suggest that an appropriately designed critical thinking class can dramatically reduce four common biases in judgment and decision making: honoring sunk costs, inferring causation from correlation, ignoring regression to the mean, and overlooking opportunity costs. The size of the debiasing effects was substantial (Cohen's d > 0.80) and persisted at least 16 months after the class ended. (PsycInfo Database Record (c) 2026 APA, all rights reserved).