Thursday, June 02, 2011

The role of theory in science

One final thought about evolutionary psych, in the wake of the Kanazawa debacle.
I spend a lot of time thinking about how to get generally smart and educated people to understand the nature of science. Despite many people's eagerness to dismiss young earth creationists as either deluded or cranks, I think their beliefs are built upon a misconception of science that is remarkably prevalent. When strongly held beliefs meet scientific evidence, the beliefs generally win.

 At the end of my history of psychology course, we read Keith Stanovich's excellent "How to Think Straight About Psychology". It is an incredibly readable philosophy of science book, applied to psychology. But even at the end, I have students who I know still doubt evolution, or hold strikingly pseudoscientific or unscientific beliefs. This is not because they are stupid, or haven't studied enough, but because science is quite often counterintuitive, and in most of our school science curriculum, we don't really teach how science works as much as a large set of science facts. Not to diminish the power of facts, because you can't organize anything if there are no facts, but science is not just a series of facts.

Darwin's first writing of theory of evolution,
in 1837, 21 years before Origin was published
One main misconception of science is the relationship between theories and facts. Evolution is a theory. So is evolution as applied to psychology. What "work" do these theories do? I think a good way of looking at a theory is as a framework for past facts and a way of finding future facts. In science, we might replace facts with observations, or experiments, since observations and experiments are the root of all facts in science. So, how can we evaluate theories as good or bad? First, a theory has to explain some portion of the current set of facts. Darwin's theory explained his finches, and other animals, but it also fit in with a larger set of observations of animals of other explorers. But we can't ignore that Darwin's theory also fit with the growing set of observations in geology about the age of the earth, about dating different fossils, or even explaining coral reefs, a mystery of the time (described beautifully in Steven Johnson's "Where Good Ideas Come From". Darwin's theory was a pretty good theory for explaining the morphology and current behavior of animals from around the world. But Darwin was dubious of his own theory, and delayed publishing it for nearly 20 years. Why? Partly because he knew the conflict it would stir with religion, but also because he wanted to collect more evidence. In other words, Darwin's theory predicted future facts and observations. If species change, and in a gradual way, and this way corresponds with environmental changes, then there should be more fossils of transitional forms. This is a key part of evolutionary theory, and of any theory. You should be able to find more facts that fit into this theory. In other words, a theory should generate hypotheses.

So where does that leave us with evolutionary psychology? Well, evolution explains a great deal of human and animal biology. How does it do with psychology? I am not a big fan of many of the evolutionary and genetic accounts of intelligence, partly because they do not square with my egalitarian beliefs, but also because they may explain some facts, but they do a crappy job of predict any new ones. If the IQ gap between blacks and whites is genetic and fixed, why is there so much evidence that IQ can be changed? Why is there the Flynn effect?

While popular imagination of science hears evolutionary psych and thinks of Kanazawa, or the Bell Curve, the theories of evolutionary psychology are many and diverse. Instead of disparaging the whole field, we should try to be more like scientists ourselves, and tease apart which individual claims of a theory have merit, and which don't. Unfortunately, this often means learning more about the set of facts that the science is trying to organize, or trusting the scientists who know those facts. Too often, instead of learning more, we look down the hole and see darkness, and assume that it is shallow, instead of asking those who have dug, who had reached, who have probed and prodded, to tell us how deep it goes.

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