Thursday, December 6, 2012

Just how bad is evolutionary psychology?

This week there was more bloggy drama because Rebecca Watson and evolutionary psychology (eg see John Wilkins).  I won't comment on the Watson-related drama, but I am interested in the evolutionary psychology (henceforth EP).

Nearly everyone on both sides of this drama agrees that popular EP is terrible.  The question is, how deep does it go? 
  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.

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.

*Since I am only waving at other examples vaguely, you are welcome to distrust my conclusions from this point on.

Part of the problem is that it's hard to guard against post-hoc theories constructed just to fit the evidence (whatever that evidence might be).  There's nothing to stop researchers from performing the experiment first and then coming up with an EP theory to justify the results.  Alternatively, it could be common wisdom that X is common, and the EP theory is created to explain X.  Occasionally it turns out that the common wisdom is mistaken, and EP theories can be falsified in this way.  Yes, EP is falsifiable!

But you can imagine there are plenty of cases where the common wisdom is correct, just not for the reasons supposed by EP researchers.  In these cases, the EP theory will never be falsified by the kind of evidence they come up with.

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 is not bad because it is politically incorrect, it is bad because it makes "obvious" predictions.  These "obvious" predictions might be wrong, falsifying the EP hypothesis.  But falsifiability is not enough, because even if the "obvious" predictions are right, there are many explanations besides EP.

Some defenses of Evolutionary Psychology

The great thing about this drama is that several people are mounting defenses of EP, making it easier for me to gather some of their points.

Chris Hallquist talks about why large brains must be an adaptation.  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.


Sciatrix said...

So I don't remember if I've mentioned this, but my field of study is the evolution of animal behavior. I'm very much not an evolutionary psychologist, but I work on a similar intersection and I'm fairly familiar with the history of both evolutionary psychology and my own broader discipline.

I don't know if you're aware of this, but in evolutionary biology "adaptationist" is a word that has a very distinct meaning and one that is also often levied as a criticism. The general idea is that you can call anything an adaptation and come up with a story explaining how it adapted, whether or not it really IS one--even though it is perfectly consistent with evolutionary theory for traits to be the result of chance or an inevitable byproduct of a different, adaptive trait. So evolutionary biologists are generally trained to view adaptation as an "explanation of last resort" and only invoke it if they have some evidence that rules out genetic drift and some evidence that says that this specific trait is causing an increase in fitness. (Usually there's some proxy for fitness used, like metabolic efficiency or number of matings achieved or something.)

If you call someone an adaptationist, you're usually implying that they are doing some sloppy thinking and have a habit of theorizing ahead of data--there's a history of people in evolutionary biology doing this and it got very bad about thirty years ago with people writing papers justifying things like a selective advantage of the depression on the human upper lip, when if you actually look at human development, that depression almost certainly exists as a byproduct of the way our heads develop as embryos.

I don't know whether evolutionary psychologists use this term differently than evolutionary biologists and sociobiologists do. My guess is that at the very least it is not so much of an insult within their field, given that in my experience of evo psych papers adaptionist ideas as I would define them crop up fairly frequently without much self-awareness. I see a lot of critiques of adaptationist thinking on the part of evolutionary psychologists.

Of course, my personal experience with evo psych papers is also limited, mostly because the bulk of my reading is in fields that are more pertinent to what I do. I will say that most of what I've read, largely papers that have been presented to me in the context of psychology courses in undergrad, has been unimpressive from an evolutionary standpoint. Obviously my sample size is limited, too, because I don't read enough evo psych to develop a thorough grasp of the literature. I can cite papers that are arguably evo psych that I did like, such as this classic paper. However, most of what I have read has not been close to this quality. Most of the quality arguably evo psych work I've read has also not necessarily been labeled as evolutionary psychology, and some people doing similar things (as with the author of the paper I linked) do not list themselves as evolutionary psychologists I don't know if the people doing that kind of work don't want to associate themselves with a poorly regarded field (evolutionary biologists particularly often have little respect for evolutionary psychologists) or if they simply prefer to place their work in the context of other related fields, such as behavior genetics, population genetics, primatology or anthropology.

I haven't yet read the paper you've linked, because this comment is getting long, but I'll skim over it later today. I do agree with you that where I have seen good evo psych, it tends to be either cross-species or else have an actual genetic mechanism for the inheritance of the behavioral trait it is studying (this category tends to be population genetic work).

miller said...

It's interesting that EP considers the adaptive hypothesis the starting point, while evolutionary biologists consider it a last resort. EP defenders see adaptationism as a research program which "time will tell" if it works. Evolutionary biologists seem to agree that it is a research program, but believe it's one that failed decades ago.

Sciatrix said...

I think it might also be that evolutionary biologists want hard evidence that something is an adaptation before deciding it's worth discussing. That is, the attitude is sure, time will tell if the trait is adaptive--but until it does, no one wants to hear about your idea that it might be, because it's all conjecture at that point. If you want to talk about it, you need to have some evidence that it's heritable and you need to have some evidence that the trait influences some measure of fitness. Otherwise your paper isn't going to make it out of peer review, for the most part. So I think there is some difference in attitude about what qualifies as generally interesting between the fields, and whether conjecturing about "maybe it works like this" is good enough for publication.

Having skimmed that paper over, the focus on the brain as working something akin to a computer with discrete modules is bothering me and reading very much as an evo-psych tendency to me. It's an attitude I've encountered in the evo psych I'm familiar with, that the brain is composed of discrete modules that don't necessarily influence each other and can be selected on without really affecting any of the others. And I don't think the evidence supports that very well. (I can go into more detail on why I think that, but it would be a rambling digression through genetics and pleiotropy and into what I know about neurobiology and behavior genetics, so I'll leave it at that for the moment.) That's actually bothering me more as a behaviorist than an evolutionary biologist, though.

From an actual evolution standpoint, I agree that he doesn't do a great job tying his arguments back to actual evolutionary processes. He's not mentioning whether for example reasoning ability is at all heritable or whether variation in suggestibility is heritable. You can't have selection without heritability. (It's also a super easy thing to measure--you take a bunch of families and plot parental means against offspring means for the trait, and then you do a linear regression of the data and find the slope. If you want to be really rigorous you do cross-fostering, which in humans means you'd study adopted children. It's not like this is hard stuff.)

They say "we don't include a mechanism, as is common in evolutionary biology" but actually including a mechanism of evolution of the trait itself is standard in evolution papers, even if no specific genetic mechanism is included. (In cases where no specific genetic mechanism is presented, you're expected to show at least that the trait is heritable, which I do not see discussed in the paper.) You have to discuss how the trait evolved, you can't just say that an evolutionary mechanism indicates that you would see this pattern of cognitive response. The closest design I can think of to what he's doing here is phylogenetic comparisons, and their sample size is way too small for that to apply as they've only got an n of one species.

...and now I really will shut up, I promise.

miller said...

Thanks for your thoughts! Massimo has a PhD in evolutionary biology, but my boyfriend has no special expertise, so it's good to get a third opinion.

One question: If something is adaptive, does that necessarily mean it is heritable? Intuitively yes, but as I recall "heritability" has a very non-intuitive meaning. It's possible, for instance, that a certain genotype is adaptive, and becomes near universal, meaning that the only remaining variation is due to environment rather than genotype. I'm not sure how to square this with the idea that adaptation requires heritability.

Sciatrix said...

No, something that is adaptive doesn't necessarily have to be heritable now. So you have a really good point about a trait that has been under heavy selection in the past, so that variation in it has been destroyed, not being currently heritable but still being adaptive. (Heritability is the proportion of phenotypic variation that can be explained by genetic variation, which I think you know but I also think is worth mentioning in case anyone else is reading. You are absolutely right that it is a non-intuitive definition!) That kind of thing leaves genetic signatures, so you can pick it up if you know the genes you're looking for. On the other hand if you're looking at the evolution of a complex quantitative trait that genetic basis can be hard to pin down.

The thing is, most evolution happens slowly enough to expect variation that is reduced by selection to be replaced by mutation. This is especially true of quantitative traits that are influenced by many genes of small effect rather than by a few genes of large effect, because there's a bigger "mutational target" to replenish that variation. Anything relating to human behavior definitely falls into that category. So I would be rather startled to find out that every possible locus impacting human arguing ability/ability to reason/insert behavioral trait here had been fixed by selection, especially given that for most of these traits there is a lot of current phenotypic variation between individuals. That would be a big finding, implying something very strange going on with the mutation rate (or perhaps just a very small effective population size, which humans as a species emphatically do not have).

I would also be suspicious of an explanation that went "this was strongly selected upon in the past, strongly selected enough that it was responsible for fairly rapid evolution of human brain function, but it's not under selection any more" which is another explanation that might take away the necessity of looking for heritability. If this used to be strongly selected upon, why is it not selected upon anymore?

miller said...

Thanks, that clears up a lot!

drransom said...

Many thanks to Sciatrix for providing the perspective that adaptive explanations are discouraged in evolutionary biology. It's very much the opposite of the way evolutionary psychology works. I'm a bit surprised that the cultures of the two disciplines have developed so differently: do evolutionary psychologists not talk to evolutionary biologists at all?