Atheists are more intelligent – but why?

When psychologists first studied the connection between religion and intelligence, in the 1920s and 30s, they came to the conclusion that atheists were more intelligent, on average, than their religious counterparts. But further research showed a murkier picture, and by the 1970s the general conclusion was that there was no difference between atheists and the religious.

More recent studies have started to shove opinion back. They seem to be showing that there is, after all, a difference – albeit with some caveats and nuances. Here’s a couple of recent ones.

Miron Zuckerman, at the University of Rochester in New York State, USA, along with colleagues has conducted a meta-analysis of all the previously-published studies. A meta-analysis is a statistical tool used to pool together different studies, so that you can see the overall picture.

Altogether, Zuckerman dug up 63 studies, dating back to the 1920s. He found that, although there was a lot of variation, there was clear evidence that “the higher a person’s intelligence, the lower the person scored on the religiosity measures”.

With this much data, Zuckerman was also able to dig a bit deeper into what factors affect the relationship. He found that the relationship is weakest in pre-college (i.e. young) individuals, and stronger for religious beliefs than for religious behaviour (i.e. church going).

Now, there are several theories on why intelligent people are less religious.

One idea is that religion is irrational, so intelligent, educated people simply ‘know better’. It’s also been suggested that intelligent people are more likely to be unorthodox. In a similar vein, Satoshi Kanazawa has suggested that religion is an evolutionary adaptation – and therefore instinctive. It takes intelligence, he suggests, to break free of our instincts. An alternative, more radical idea from Darren Sherkat is that the culture of religious fundamentalists actually impedes their intellectual development.

Zuckerman and colleagues looked at four so-called ‘time-gap’ studies, in which intelligence was measured at an early age and then religion was assessed later. Taken together, these suggest that intelligence can predict your religiosity in later life. 

They also looked at two studies of gifted children. These studies found that intelligent children were less likely to be religious later – but that the religiosity of their upbringing had little influence over their religion in later life.

Now, you should take these findings with a pinch of salt in light of other research which shows the powerful influence of upbringing on religious belief – and given that in the US (where these studies were conducted) people usually have a religious upbringing. That limits the possibilities for intelligent people to become more religious!

But the idea that intelligence turns people off religion fits nicely with the results of the second study.

Francisco Cribari-Neto and Tatiene Souza are statisticians at the Universidade Federal de Pernambuco and the Universidade Federal da Paraíba, respectively, in Brazil.

They’ve taken a look at a how the average IQ seen in different countries varies with average religiosity. The idea is to see whether religious culture is related generally to intellectual life. Now, this has been done before (by Richard Lynn in 2009), but Cribari-Neto and Souza have taken a rather more sophisticated approach.

They were able to show that the link is real, and that it is independent of economic development (both intelligence and loss of religion are independently linked to economic development, but there is something additional to that). What’s more, the effect is strongest in nations at middling levels of average IQ – as shown in the figure.

The reason for this, they suggest, is that at low IQs there is little scope for critical reasoning. And at high IQs most of the potential effect of critical reasoning have already happened (as the nation transitioned from lower IQs. So it is the middle range of IQs that the effect of increasing IQ is most clearly seen.

Of course, because it’s a correlation you can’t rule out the reverse effect. But it does all seem to fit together nicely.

Zuckerman M, Silberman J, & Hall JA (2013). The Relation Between Intelligence and Religiosity: A Meta-Analysis and Some Proposed Explanations. Personality and social psychology review : an official journal of the Society for Personality and Social Psychology, Inc PMID: 23921675
Francisco Cribari-Neto, & Tatiene C. Souza (2013). Religious belief and intelligence: Worldwide evidence Intelligence, 482-489 DOI: 10.1016/j.intell.2013.06.011

This article by Tom Rees was first published on Epiphenom. It is licensed under Creative Commons.