The theory of evolution by natural selection is among the best established in science, yet also among the most controversial for subsets of the American public.
For decades we've known that beliefs about evolution are well-predicted by demographic factors, such as religious upbringing and political affiliation. There's also enormous variation in the acceptance of evolution across different countries, all of which suggests an important role for cultural input in driving beliefs about evolution. A child raised by Buddhists in California is much more likely to accept evolution than one raised by evangelical Protestants in Kansas.
But in the last 20 years or so, research in psychology and the cognitive science of religion has increasingly focused on another factor that contributes to evolutionary disbelief: the very cognitive mechanisms underlying human cognition.
Researchers have argued that a variety of basic human tendencies conspire to make natural selection especially aversive and difficult to understand, and to make creationism a compelling alternative. For instance, people tend to prefer explanations that offer certainty and a sense of purpose when it comes to their lives and the design of the natural world and they have an easier time wrapping their heads around theories that involve biological categories with clear boundaries — all of which are challenged by natural selection.
These factors are typically taken to hold for all humans, not only those who reject evolution. But this naturally raises a question about what differentiates those individuals who do accept evolution from those who do not. In other words, if the California Buddhist and the Kansas Protestant share the same cognitive mechanisms, what accounts for their differing views on evolution?
In fact, there's evidence that individuals vary in the extent to which they favor purpose and exhibit other relevant cognitive tendencies, and that this variation is related to religious belief — itself a strong predictor of evolutionary belief. But there's a lot we don't know about how differences between individuals drive different beliefs about evolution, and about how these individual differences interact with cultural input.
A new paper by psychologist Will Gervais, just published in the journal Cognition, sheds new light on these questions. In two surveys conducted with hundreds of undergraduates attending a large university in Kentucky, Gervais found an association between cognitive style and beliefs about evolution. Gervais used a common task to measure the extent to which people engage in a more intuitive cognitive style, which involves going with immediate, intuitive judgments, versus a more analytic cognitive style, which involves more explicit deliberation, and which can often override an intuitive response.
In both studies, Gervais found a statistically significant relationship between the extent to which individuals exhibited a more analytic style and their endorsement of evolution. Importantly, the relationship remained significant even when controlling for other variables that predict evolutionary beliefs, including belief in God, religious upbringing and political conservatism.
The study also replicated prior work that has found a relationship between religiosity and evolutionary beliefs, and between cognitive style and religious disbelief: Participants with a more analytic style were not only more likely to accept evolution, but also to indicate lesser belief in God.
These findings are consistent with at least three possibilities. The first — suggested by the clever title of Gervais' paper, "Override the Controversy" — is that all individuals have a tendency to reject evolution on an intuitive level, but that some individuals engage in a form of analytic or reflective thinking that allows them to "override" this intuitive response.
A second possibility is that some individuals have stronger intuitive responses than others. Such individuals are likely to experience a stronger pull toward purposive thinking, a greater aversion to uncertainty and other cognitive preferences at odds with evolution. If their intuitive responses are generally stronger, they're also less likely to succeed in overriding them by engaging in analytic or reflective thought.
Yet, a third possibility — and one I find compelling — is that effects of cognitive style interact with cultural input. Creationism and belief in God might be "intuitive" for many Kentucky undergraduates not only because these beliefs align well with basic human tendencies, but also because these are the beliefs they grew up with and that dominate their communities. What might require analytic and reflective thought isn't (just) overriding cognitive systems that govern intuition, but overriding the norms of one's upbringing and peers.
These possibilities are neither mutually exclusive nor exhaustive. The fact is, there's a lot we don't know and the reality is likely to be complex. But the new findings by Gervais — and the findings on which they build — already point to the richness of human belief. Evolution isn't controversial for scientific reasons, but it is controversial, in part, for psychological reasons.
Understanding those reasons won't only have practical implications for science education and policy, but also can tell us something about the basic building blocks of the mind — and about how they interact with our social and cultural environment.
Tania Lombrozo is a psychology professor at the University of California, Berkeley. She writes about psychology, cognitive science and philosophy, with occasional forays into parenting and veganism. You can keep up with more of what she is thinking on Twitter: @TaniaLombrozo