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Moving The Goalposts In Evolutionary Psychology

I'm not usually in the habit of refereeing other bloggers' disputes, but a recent exchange between Todd Zywicki and PZ Myers got under my skin. Zywicki started things off by drawing an implicit parallel between conservative opposition to evolution and liberal opposition to evolutionary psychology. He challenges liberals to answer four questions. In the interest of getting my views on the table, I'll take a moment to answer:

1. Are differences between men's and women's aptitudes solely a result of society and culture, or is there an evolutionary basis for some of those distinctions?
Of course there are evolutionary differences between men and women. But these differences are 1) very small compared with the range of interpersonal variability, and 2) heavily mediated by culture. It's usually a mistake to see genetics as the proximate cause of any human behavior (particularly controversial or politically significant behavior).

2. Do you think that schools should expose children to the scientific hypothesis that evolution has produced innate differences between men and women that partially explains differences in interests and aptitudes, or should they teach that all differences are socially-constructed?
Schools should not be in the business of exposing children to hypotheses -- after all, there are countless scientific hypotheses out there. Schools should be in the business of teaching 1) how science works, and 2) the content of scientific theory -- that is, those hypotheses that have stood up to a great deal of scientific scrutiny and been accepted by most experts in the field.

3. Do you believe that Harvard's faculty was correct in censuring President Larry Summers for offering the hypothesis that differential performance by men and women in math and science achievement at elite universities may be in part the result of differential distribution of natural abilities in math and science between men and women at several standard deviations above the mean?
Summers didn't offer a hypothesis. He asserted a conclusion (albeit couched in some weasel words). And he did so in his capacity as President of Harvard, thus implying that Harvard's training and hiring of scientists would be based on the view that differences in achievement are innate (and hence there's nothing the university can do about them).

4. Do you believe that the theory of evolution applies to the evolution of mental traits as well as physiological traits?
It depends on what you mean by "traits." Certainly the brain has evolved the trait of being flexible and programmable. But it's clearly incorrect to say that all of the ideas, inclinations, and thought processes in the brain are hard-wired by evolution.

PZ Myers responded with a set of answers largely similar to mine, then declared (in his characteristically nasty way) evolutionary psychology to be "a load of poorly done hokum." Let's pause here for a definitional clarification. In his first three questions, Zywicki implicitly defined EP as the claim that there are significant differences in aptitude between the sexes, and that these differences are evolved. This definition -- let's call it EP1 -- is consistent with the issues at stake in most punditry on EP (and with my definition of EP in an earlier post). Myers' argument is that EP1 is at best controversial, and at worst rejected, among those scientists who study these things.

Zywicki updated his original post, charging that Myers's dismissal of EP1 meant that he must disagree with a whole host of widely-accepted findings, such as "the innate ability to acquire culture, the unusual degree of plasticity of human minds relative to other species, ... [and] an innate ability to detect intentionality." Here we see a clear shifting of the goalposts. Zywicki is now talking about evolutionary psychology as implicitly defined in his fourth question -- the more general claim (call it EP2) that the human brain is the result of evolution. There's no reason that rejection of EP1 entails rejection of EP2 -- indeed, Myers's post asserted as fact several of the claims Zywicki lists for EP2, and it's Myers's very commitment to a strong version of those EP2 claims about the evolved flexibility of the brain that leads him to reject EP1's claims of detailed hardwiring. He even links approvingly to an interview with David J. Buller, who makes a distinction between "Evolutionary Psychology" (EP1) and "evolutionary psychology" (EP2), declaring only the former to be bad science.

After Myers unleashes some ad hominem in the comments to his own post, Zywicki accuses him of a move similar to that made by Intelligent Design proponents -- picking at disputes and questionable conclusions on the edges of a paradigm in order to impugn the validity of its core. This is only a correct assessment of Myers's argument if you insist on taking "EP1 is bunk, EP2 is fine" to mean "both EP1 and EP2 are bunk." And Zywicki seems to be advocating a move that's just the reverse of the IDers' strategy. He's claiming that since the core of the EP paradigm (EP2) is solid, then controversial propositions at its fringe (EP1) must be true as well.


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