In a controversial piece of research that is sure to ignite debate, US researchers have concluded that religious people are more likely to have lower IQs than non-religious people.
The University of Rochester researchers found there was "a reliable negative relation between intelligence and religiosity" in 53 of 63 studies they reviewed.
The studies began as early as the 1920s, and each was analysed independently for data collection method, sample size and analysis used.
Only two of the studies showed religious people had higher intelligence, and 35 strongly suggested they had lower intelligence.
The authors suggested a number of reasons for their findings.
"Intelligent people tend to adopt an analytic, as opposed to intuitive, thinking style, which has been shown to undermine religious beliefs," they wrote in Personality and Social Psychology Review.
"Intelligent people are less likely to conform and, thus, are more likely to resist religious dogma. And several functions of religiosity, including compensatory control, self-regulation, self-enhancement, and secure attachment, are also conferred by intelligence. Intelligent people may therefore have less need for religious beliefs and practices."
The three researchers, who are all psychologists, found the trend starts in childhood, with intelligent children more likely to shun religion than individuals with average intelligence.
They also found elderly people with higher IQs are less likely to follow a religion.
They found no such correlation between other factors, such as gender or education, and intelligence.
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