During a sabbatical at the University of Cambridge in 1991, a Canadian psychologist called Keith Stanovich decided to address these issues head on. With a wife specializing in learning difficulties, he had long been interested in the ways that some mental abilities may lag behind others, and he suspected that rationality would be no different. The result was an influential paper introducing the idea of dysrationalia as a direct parallel to other disorders like dyslexia and dyscalculia.

It was a provocative concept—aimed as a nudge in the ribs to all the researchers examining bias. “I wanted to jolt the field into realizing that it had been ignoring individual differences,” Stanovich told me.

Stanovich emphasizes that dysrationalia is not just limited to system 1 thinking. Even if we are reflective enough to detect when our intuitions are wrong, and override them, we may fail to use the right “mindware”—the knowledge and attitudes that should allow us to reason correctly. If you grow up among people who distrust scientists, for instance, you may develop a tendency to ignore empirical evidence, while putting your faith in unproven theories. Greater intelligence wouldn’t necessarily stop you forming those attitudes in the first place, and it is even possible that your greater capacity for learning might then cause you to accumulate more and more “facts” to support your views.