Tuesday, November 20, 2007

Evolutionary psychology as an “extraordinary claim”

Channeling David Hume, Carl Sagan famously said, "extraordinary claims require extraordinary evidence". As Richard Dawkins notes in the Afterword to Buss (2005), evolutionary psychology [EP], oddly, is often thought to make extraordinary claims meriting strong skepticism. Now, clearly, to accept the proposition that telepathic communication is occurring in a particular case, we would require extraordinary evidence and "demand multiple replications under ultrarigorous, double-blind controlled conditions, with a battery of professional illusionists as skeptical scrutineers and with a statistical p-value less than one in a billion" (2005: 977). On the other hand, the claim that, say, two people can communicate via a telephone or by exchanging letters would elicit practically no skepticism. In between these extremes are claims that one ought to be somewhat skeptical about and require a good deal (but not an extraordinary amount) of evidence before they can be accepted provisionally. Examples of this class include the proposition that smoking causes cancer (when it was first posited) and the claim that, say, cocaine has epigenetic effects on the hippocampus. The difference between the cases, it would seem, has to do with a priori plausibility: the extent to which the proposition under consideration fits in with everything else we know about the world. So where on this spectrum does evolutionary psychology fall?

Dawkins makes a convincing case that many critics of EP incorrectly place it on the telepathy end of the spectrum when it belongs in the middle, much nearer to the plausible end. Evolutionary psychology, notes Dawkins, "amounts to the exceedingly modest assertion that minds are on the same footing as bodies where Darwinian natural selection is concerned" (2005: 978). Indeed, it is the opposite conclusion – that human psychology is exempt from the forces that govern the rest of the natural world – that requires extraordinary evidence. It is the proposition that humans are unique, and somehow not continuous with the natural world, that is a priori implausible given everything else we know. Dawkins makes the same argument with respect to modularity: since "modularity is a universally good design principle which pervades engineering, software, and biology" and since it "is such an obvious way to run any complex operation, we should positively expect that the mind would be modularized" (2005: 978, emphasis added). The controversy over modularity of mind is therefore often so heated because its opponents are far more skeptical of it than they ought to be.

While I think Dawkins is exactly right when it comes to the many of EP’s critics, it is only fair to note that there is a group of people who don’t make the mistakes he discusses. Some cognitive scientists and cognitive psychologist accept the mind is a product of the brain and agree the brain evolved by natural selection, but then deny an evolutionary perspective is illuminating. (see this blog post). While we should expect an evolutionary perspective to offer insights, it is possible to adopt a functionalist perspective (a "design stance" in Dennett’s parlance) without being explicitly evolutionary. (Indeed, a good deal was discovered about human physiology using this method long before the publication of Darwin’s theory). Nonetheless, it is still clear that this sub-class of EP's critics ought to locate particular EP propositions – say, that female mate preference varies with menstruation cycle – in the middle of the skepticism spectrum, not at the telepathy end. Sometimes it seems that even these critics – such as the blog entry liked above – fail to do so and I can't help but detect antipathy bordering on bias.


Dawkins, R. (2005) “Afterword,” in Buss, M. (ed.) Handbook of Evolutionary Psychology (Hoboken, NJ: John Wiley & Sons)

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