May 31 2012

Richard Leakey, Evolution and Motivated Reasoning

Richard Leakey, son of Mary and Louis Leakey, is a deservedly famous paleoanthropologist who has contributed significantly to our understanding of human evolution. In a recent interview he expressed his confidence that skepticism over evolutionary theory will fade away over the next 15-30 years. He is quoted as saying:

“If you get to the stage where you can persuade people on the evidence, that it’s solid, that we are all African, that color is superficial, that stages of development of culture are all interactive,” Leakey says, “then I think we have a chance of a world that will respond better to global challenges.”

While I hope this is true, I am not as optimistic. I think the primary problem with his argument is the premise that you can get to the stage, “where you can persuade people on the evidence.”  In my opinion the evidence indicates that for many people, you cannot persuade them on the evidence. Unfortunately, human psychology simply does not work that way.

I agree with his premise that the evidence for evolution as a fact is overwhelming. In fact, I think we are already there. We do not need to wait 15-30 years for the evidence to be solid and convincing. There is a confluence of evidence from genetics, paleontology, anatomy, and developmental biology that has only one scientific explanation – common ancestry and organic evolution. We’re still working out the details, but the big picture is crystal clear.

Leakey says:

“You can lay out all the fossils that have been collected and establish lineages that even a fool could work up. So the question is why, how does this happen? It’s not covered by Genesis. There’s no explanation for this change going back 500 million years in any book I’ve read from the lips of any God.”

He seems to be agreeing with my position – the fossils are already so compelling that “even a fool” can see the obvious connection. So why, then, are there so many people who doubt evolution?

The key variable seems to be how tightly held a belief is. For those ideas and claims about which we do not have any serious emotional investment, we can behave rationally and follow the evidence wherever it leads. For those ideas in which we have an emotional stake, however, humans seem to have an unlimited capacity for what is called “motivated reasoning.” We are really good at finding reasons to dismiss ideas or evidence we don’t like, and for accepting notions we prefer, no matter how absurd and contradicted by evidence they may be.

Psychologist Kunda wrote in 1990 about motivated reasoning:

It is proposed that motivation may affect reasoning through reliance on a biased set of cognitive processes–that is, strategies for accessing, constructing, and evaluating beliefs. The motivation to be accurate enhances use of those beliefs and strategies that are considered most appropriate, whereas the motivation to arrive at particular conclusions enhances use of those that are considered most likely to yield the desired conclusion. There is considerable evidence that people are more likely to arrive at conclusions that they want to arrive at, but their ability to do so is constrained by their ability to construct seemingly reasonable justifications for these conclusions. These ideas can account for a wide variety of research concerned with motivated reasoning.

Since then research has reinforced the notion of motivated reasoning. A recent study, for example, concludes:

Three cognitive mechanisms are identified: a prior belief effect, confirmation bias, and disconfirmation bias.

We tend to hold onto a belief we already have, and we tend to seek out and accept confirming evidence while finding reasons to dismiss contrary evidence. Further, in a study by Nyhan and Reifler subjects who were given correct information that contradicted a tightly held political belief actually strengthened their original belief, in a so called “backfire effect.” Being subjected to information that contradicts their desired belief seemed to activate their motivated reasoning and cause them to dig in their heels even harder.

Anyone who has dealt with creationists should be familiar with the degree of motivated reasoning involved. Examples are legion. I was just sent a news item (an almost daily occurrence) reporting about a man from Georgia called Bob Staples who believes that evolution should not be taught in public schools. In a letter to the state board science committee he wrote:

“Presenting evolution as fact should be a concern to all Georgians. That evolution is not a fact of science and shouldn’t be taught.”  “To teach it as a fact is lying to people.”

He also claims:

“The crime rate, child abuse, divorce. All of these things rose from a period following the implementation of teaching Darwinian Theory.”

That last bit is classic confirmation bias. Crime rate has risen and fallen over the last century. In any case, these are complex social phenomena and it is ludicrous to assign cause and effect to a single factor, especially one that would have such an indirect effect such as the teaching of evolution (besides, I thought it was rock and roll that was the cause of all modern social ills). We could just as easily point to many of the positive social trends, like decreased discrimination, and credit the teaching of evolution.

If simply providing more and more evidence for the fact of evolution is not going to change the minds of people like Staples, then what will? I wish I knew. There doesn’t seem to be any magic formula. My guess, and a major motivation for my skeptical activism, is that giving people critical thinking skills can only help. We need to shift our motivation away from any one particular conclusion and toward being logically valid and correct on the facts. If people are more motivated to be rational than to be correct on any one point, they should be more likely to engage in effective (rather than motivated) reasoning.

We need to also give them the cognitive skills to reason effectively. This involved educating the public about logic, scientific methodology, and so-called metacognition – thinking about thinking.

There is no point in arguing with a creationist who is stuck is a creationist world view, who is engaged in motivated reasoning, and who does not have the intellectual tools to analyze their own logical fallacies and cognitive biases. If you teach them critical thinking, however, they might at some point turn their critical thinking skills to their own evolution denial. I have seen it happen.


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