The prevailing view is that people adopt false beliefs because they’re too stupid or ignorant to grasp the truth. This may be true in some cases, but just as often the opposite is true: many delusions prey not on dim minds but on bright ones. And this has serious implications for education, society, and you personally.
In 2013 the Yale law professor Dan Kahan conducted experiments testing the effect of intelligence on ideological bias. In one study he scored people on intelligence using the “cognitive reflection test,” a task to measure a person’s reasoning ability. He found that liberals and conservatives scored roughly equally on average, but the highest scoring individuals in both groups were the most likely to display political bias when assessing the truth of various political statements.
In a further study (replicated here), Kahan and a team of researchers found that test subjects who scored highest in numeracy were better able to objectively evaluate statistical data when told it related to a skin rash treatment, but when the same data was presented as data regarding a polarizing subject—gun control—those who scored highest on numeracy actually exhibited the greatest bias.
The correlation between intelligence and ideological bias is robust, having been found in many other studies, such as Taber & Lodge (2006), Stanovich et al. (2012), and Joslyn & Haider-Markel (2014). These studies found stronger biases in clever people on both sides of the aisle, and since such biases are mutually contradictory, they can’t be a result of greater understanding. So what is it about intelligent people that makes them so prone to bias? To understand, we must consider what intelligence actually is.