This is a repost of an article I wrote in 2012.  This is one of the things I had in mind when I recently wrote “So you want to discredit an academic field“.  It’s super old, so I felt it needed some light editing for clarity, and to remove references to old drama nobody cares about.

Both critics and defenders of evolutionary psychology (henceforth EP) agree that popular EP is terrible.  The question is, how deep does it go?  There are four possibilities:

1. Journalists are misinterpreting and exaggerating studies.
2. Journalists understand correctly, but pick out terrible studies from a generally reputable field.
3. There are large sections of EP which are just bad, but attract more media attention.
4. EP is rotten all the way through.

Case study: Argumentative Theory

The trouble is that you can hardly talk about EP without talking about specific examples of EP.  And if you only have a few examples, people can accuse you of not having a large enough survey.  But it’s hard to investigate more than a few examples, because we’re lazy and/or have jobs.

I’m among those people who are lazy and/or have jobs, so I’m just going to use one example, and it’s not even a new example.  I wrote about this in 2011:

Someone sent me a link to a NY Times article called “Reason Seen More as Weapon Than Path to Truth“. […]  It’s about “argumentative theory”, which claims that human reasoning evolved to win arguments, rather than to reach truth.  In this view, even our many cognitive biases are adaptations to improve debate skills.  This goes against the more common view that cognitive biases represent limitations of natural selection.

Given these two diverging views, I was curious about the evidence for each side.  But I was disappointed in how little evidence the article presented.  In fact, it presented no evidence at all!  I’ve decided the article is a self-referential parody.

So the NY Times article was terrible.  But was it terrible because there’s no evidence for argumentative theory, or is it terrible because the journalist botched the evidence for argumentative theory?  The answer lies buried in this fifty-page review on which the NY Times article was based.

Yeah, I’m not going to read through fifty pages.  But my boyfriend read through it.  He said that it was a good review of fallacies and cognitive biases, but did not advance any other kind of evidence for argumentative theory.  In his opinion, the biggest hole in the paper was its failure to give any account of the evolution of persuadability.  How can anyone win arguments if no one ever gets persuaded?  I asked him if the paper at least showed evidence that cognitive biases lead to winning more arguments, and in his recollection it did not.

Naturally I’m obligated to believe what my boyfriend says, but you’re welcome to look at the paper yourself.  Massimo Pigliucci also read the paper independently, and had an even more negative opinion.

But maybe this is just one bad paper that the journalists picked out because it was bad.  It’s hard to say without being familiar with the field.  However, there are measures that even a non-expert can use.  According to the Web of Science, “How do Humans Reason? Arguments for Argumentative Theory” was the most cited paper in Behavioral and Brain Sciences in 2011, receiving 38 citations.  As for Behavioral and Brain Sciences, it has the highest impact factor in the category of behavioral science, and third highest impact factor in the category of neuroscience. It’s possible that all 38 citations are saying, “Look at this terrible paper”, but I doubt it; by all accounts this is a very authoritative paper. [2018 note: it now has over 1300 citations, although I noticed that a lot of them are coming from outside EP.]

Now that doesn’t mean that all of EP is bad.  It could be that only one segment of EP is bad, a large enough segment to cite this paper 38 times.  Given that even anti-EP people agree that at least some parts of EP are decent, this is a good place to settle our inquiry.

TL;DR: I read an awful article about EP, and found that the awfulness comes from the researchers, not the journalists.  It was also a very authoritative study in its field, though this does not imply that all of EP is bad, just parts of it.

Discussion: What is the problem?

First let me note that there is nothing politically “incorrect” or “correct” about argumentative theory.  I have no problem with it, and argumentative theory seems like a reasonable possibility.  Unlike many of the other EP studies that people complain about, it clearly has nothing to do with race or sex.  You may hypothesize that people oppose EP because its conclusions are at odds with liberal politics.  My own hypothesis is that the racism and sexism just draws people’s attention to the shoddy arguments that exist in EP.

And what are those shoddy arguments?

If I may generalize based on the above case study and a few other examples I have seen, evidence for EP (at least that which appears in major media) comes in this form: Based on our theory, human evolution should have selected for trait X.  We did an experiment confirming the prevalence of X across cultures.

But you can imagine there are plenty of cases where the observation of X is correct, just not for the reasons supposed by EP researchers.

In the case of argumentative theory, an alternative hypothesis that correct reasoning is more adaptive, but also costs a lot of other resources, or is otherwise difficult for evolution to achieve.  The paper points at all our cognitive hiccups, but this is just as consistent with my theory as it is with argumentative theory.  You can also imagine other reasons why cognitive biases might be adaptive.  For example, perhaps they allow you to lose arguments more often, which is good because winning arguments doesn’t win friends.  Or cognitive biases could lead to more cautious behaviors (eg mistaking the wind for a tiger is better than mistaking a tiger for the wind).

TL;DR: The study’s badness doesn’t come from being politically incorrect.  It makes predictions, and shows evidence confirming the predictions, but does not do enough to rule out alternative explanations of the same predictions.  The theory is technically falsifiable, but falsifiability is not enough.

Some defenses of Evolutionary Psychology

Chris Hallquist talks about why large brains must be an adaptation [2018 note: links to Hallquist are now broken].  Big brains are very costly, so there has to be some adaptive value to offset this.  He also mentions the theory that women are more “picky” about sex partners than men because women have to invest more in children.  This theory is evidenced by a cross-species study which verifies that in animal species with two sexes, the sex with more investment in offspring is the pickier one.

Those kinds of evidence overcome my objections, and so I do not object to them.  There could be further objections that I am not aware of, but for now I accept the null hypothesis that this is good science.  However, neither of these arguments apply to argumentative theory, which I still think is bad science.

Ed Clint also gives a quote by Elliot Sober from Philosophy of Biology:

Adaptationism is first and foremost a research program. Its core claims will receive support if specific adaptationist hypotheses turn out to be well confirmed. If such explanations fail time after time, eventually scientists will begin to suspect that its core assumptions are defective. Phrenology waxed and waned according to the same dynamic (Section 2.1). Only time and hard work will tell whether adaptationism deserves the same fate ( Mitchell and Valone 1990).

My interpretation of this quote is that adaptationism is not the assumption that everything is adaptive, it is a way of picking research topics.  You look at a trait and start with the theory that it is adaptive, not because you believe it’s true, but because among all the possible hypotheses that’s the best one to start with.  (This could be compared to methodological naturalism.)  Something like argumentative theory is just the beginning of a project.  And once argumentative theory becomes a big enough question, scientists will finally perform a solid, expensive experiment.  (I’m sure the cross-species study, for instance, must be quite expensive.)

I believe my interpretation is corroborated by this EP FAQ linked by Ed Clint:

It is true that many functional hypotheses have been offered for a variety of psychological phenomena, and it is also true that most of these hypotheses are probably wrong. However, hypotheses outnumber established theories in just about any field you care to name, and evolutionary psychologists are no less discriminating than other scholars.

I think this is a fair defense of EP, though it leaves a few questions.  Why do researchers so happily talk about their hypotheses to the media as if they were true?

And at most, it leads me to a middle ground between the two sides.  If I read a story, or a scientific study proposing an adaptive explanation for a human trait, should I believe it?  No, I should not.  Because in the field of EP, the adaptive hypothesis is just the starting hypothesis.  It’s the idea that the researchers toss around, until it gains enough weight and they bring in the real evidence.  Should I believe in argumentative theory?  No, not at all.  Should I believe in the pickier women theory?  Yes, but only after I heard about the cross-species research.

TL;DR: There are some kinds of evidence in EP that I find persuasive, such as cross-species research.  Another defense of EP is that adaptationism is not so much an assumption of EP, as it is simply a good starting point.  If that is the case, then I should reject adaptive claims from EP until I’m sure that they’ve advanced beyond the starting point.

2018 postscript: Oof, some of my writing in the middle section was really bad, so I hope the edits helped.  I’d like to add that my friend Sciatrix, an evolutionary biologist, commented on this article, criticizing this “adaptationism as a research program” idea, and criticizing the argumentative theory paper.