Whatever one thinks of the study referenced below, one has to admire the choice to illustrate the point:
As for the substance of the study, here is the abstract:
Despite their important implications for interpersonal behaviors and relations, cognitive abilities have been largely ignored as explanations of prejudice. We proposed and tested mediation models in which lower cognitive ability predicts greater prejudice, an effect mediated through the endorsement of right-wing ideologies (social conservatism, right-wing authoritarianism) and low levels of contact with out-groups. In an analysis of two large-scale, nationally representative United Kingdom data sets (N = 15,874), we found that lower general intelligence (g) in childhood predicts greater racism in adulthood, and this effect was largely mediated via conservative ideology. A secondary analysis of a U.S. data set confirmed a predictive effect of poor abstract-reasoning skills on antihomosexual prejudice, a relation partially mediated by both authoritarianism and low levels of intergroup contact. All analyses controlled for education and socioeconomic status. Our results suggest that cognitive abilities play a critical, albeit underappreciated, role in prejudice. Consequently, we recommend a heightened focus on cognitive ability in research on prejudice and a better integration of cognitive ability into prejudice models.
Gordon Hodson, one of the authors of the study, was quoted in a Live Science article:
Hodson was quick to note that the despite the link found between low intelligence and social conservatism, the researchers aren’t implying that all liberals are brilliant and all conservatives stupid. The research is a study of averages over large groups, he said.
“There are multiple examples of very bright conservatives and not-so-bright liberals, and many examples of very principled conservatives and very intolerant liberals,” Hodson said.
All of this reminds me of the controversy surrounding The Bell Curve by Richard Herrnstein and Charles Murray. The book asserted that cognitive ability can be expressed in a meaningful single number (g) and that it is substantially, though not completely, the result of genetics.
The book also argued that IQ tests accurately measure this ability and that those tests can be designed to eliminate bias. That led to controversy because the authors asserted that racial differences in IQ were real (blacks, for instance, tend to score lower on IQ tests than whites) and like all differences in IQ involves an important genetic component (so they argued).
Now, there was a raging debate after the publication of The Bell Curve and the author’s analysis was found to be wanting by many critics. Right now all I can offer is that I distrust such studies. We don’t yet know enough about how the brain works to pronounce with confidence the relationship between “intelligence” (the definition of which is also problematic) and performance on IQ tests or the adoption of a set of beliefs.
But I do think there is validity in the idea that low intelligence folks tend to prefer black and white explanations of an otherwise complicated reality, and that would apply to people on the left and right as far as I can tell. (But some intelligent folks prefer the black and white explanations presumably because of the emotional comfort involved, so go figure.)
But I do like the idea that Donald Trump is the poster child for the alleged link between low intelligence and racism and conservative beliefs.