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Rationality and Belief in Human Evolution
Dan M. Kahan
Keith E. Stanovich
This paper examines two opposing theories of disbelief in evolution. One, the “bounded rationality” account, attributes disbelief to the inability of individuals to suppress the strongly held intuition that all functional systems, including living beings, originate in intentional agency. The other, the “expressive rationality” account, holds that positions on evolution arise from individuals’ tendency to form beliefs that signal their membership in and loyalty to identity-defining cultural groups. To assess the relative plausibility of these theories, the paper analyzes data on the relationship between study subjects’ beliefs in evolution, their religiosity, and their scores on the Cognitive Reflection Test (CRT), a measure of critical-reasoning proficiencies including the disposition to interrogate intuitions in light of available evidence. Far from uniformly inclining individuals to believe in evolution, higher CRT scores magnified the division between relatively religious and relatively nonreligious study subjects. This result was inconsistent with the bounded rationality theory, which predicts that belief in evolution should increase in tandem with CRT scores for all individuals, regardless of cultural identity. It was more consistent with the expressive rationality theory, under which individuals of opposing cultural identities can be expected to use all the cognitive resources at their disposal to form identity-congruent beliefs. The paper discusses the implications for both the study of public controversy over evolution and the study of rationality and conflicts over scientific knowledge generally.