February 12th is Darwin Day, the anniversary of Darwin's birth and an excuse for scientists, educators, and Darwin enthusiasts worldwide to celebrate the theory of natural selection and its central role throughout the biological and social sciences.

While scientists overwhelmingly accept natural selection as a well-established scientific theory, it's rejected by a sizable minority of Americans, especially as an explanation for human origins.

What makes natural selection so unpalatable to so many people? And what makes alternatives, such as Intelligent Design and creationism, so attractive?

The answers to these questions are no doubt complex, and every individual has his or her own reasons for belief. Nonetheless, a growing body of research spanning the cognitive sciences suggests that powerful psychological mechanisms shape the explanations that people tend to find satisfying and ultimately accept.

This post is the first in a series inspired by Darwin Day that explores why people find evolution difficult to understand and to accept, and why Intelligent Design and creationism might be more compelling.

In this post I'll consider a provocative paper published in 2010 by Bastiaan Rutjens, Joop van der Pligt, and Frenk van Harreveld from the University of Amsterdam. They examined how a reminder that one can't always control life's outcomes influenced people's preferred explanations for life on earth. Specifically, they wondered whether feeling a lack of control would lead people to reject explanations that involve random chance (namely natural selection) in favor of explanations that suggest a more orderly and predictable world.

The experimenters first assigned their undergraduate participants to one of two groups. In the first group (call them the powerless group), participants were encouraged to think of themselves as powerless in the face of an unpredictable universe. They first recalled an unpleasant situation in which they lacked control and were then asked to provide three reasons to believe that the future is uncontrollable. In the second group (call them the powerful group), participants were encouraged to think of themselves as powerful agents in an orderly universe: They were asked to recall an unpleasant situation in which they did have some control and to provide three reasons to believe that the future can in fact be controlled.

Participants were then presented with descriptions of evolution and Intelligent Design and asked to choose the theory that "provides the best framework to explain the origin of life on this planet." The description of evolution emphasized the role of random processes and chance:

"...Natural selection, the basis of this theory, is generally an unstructured and random process in which unpredictable features of the natural environment determine how life evolves."

In contrast, the description of Intelligent Design focused on the role of an overseeing and controlling designer:

"...Contrary to evolutionary theory, which explains life on our planet as the results of random processes, ID theory posits that, given the complexity of our planet, its design requires an external agent."

Overall, participants tended to choose natural selection over Intelligent Design.* However – and this is the key – they were much less likely to do so when their sense of control was threatened. Participants in the powerful group chose Intelligent Design less than 5% of the time, but those in the powerless group chose it over 20% of the time! In other words, feeling a lack of control sent participants in search of a designer.

But is God or some other external agent the only remedy for the existential malaise induced by confronting one's powerlessness in an uncontrollable world?

Not necessarily. The researchers cleverly considered a third possible explanatory framework: a version of natural selection inspired by Conway-Morris that characterized evolution as a predictable and orderly process. The description explained that "life on our planet is not the result of random processes: if evolution would be replayed, results would inevitably be similar to the present state of affairs."

Given the choice between "random" natural selection and this predictable form of evolution, participants tended to prefer the familiar random option. But they were much less likely to choose the random option if they were in the powerless group. Only about 5% of participants in the powerful group opted for the Conway-Morris version of evolution. But when participants' sense of control was challenged in the powerless group, over 30% did so! As before, feeling a lack of control pushed participants towards the more orderly universe, but in this case it was one that did not invoke a designer.

The researchers also pitted one orderly universe against the other: Intelligent Design versus the Conway-Morris version of evolution. When these were the options, manipulating participants' sense of control no longer had a measurable effect. Confronted with two options that promised order and predictability, feeling powerless no longer gave Intelligent Design an edge relative to evolution.

Some lessons are clear: Feeling a lack of control can push people towards explanations that suggest a predictable and orderly world, but embracing an ultimate designer isn't the only option.

Other lessons are less clear. Does this explain why any given individual does or does not accept evolution? Probably not. And do findings of this kind tell us anything about what ACTUALLY explains the biological world as opposed to what people BELIEVE explains it? That turns out to be a complicated and controversial question, which I'll return to in a Darwin Day post next month. Stay tuned!

* Remember that participants were university students, presumably in Amsterdam. While approximately 70% of people polled in the Netherlands agreed with the statement that "Human being, as we know them, developed from earlier species of animals," only about 40% of Americans did so (Miller, Scott, & Okamoto, 2006).

** The Image above comes from here, where you can find additional Darwinalia.