In defence of Evolutionary Psychology

Holmes asked me to open a new thread on this in A great article about reproductive freedom. I'll respond to his and EZScience's messages here.I wrote: EZScience responded: My initial phrasing was sloppy, I honestly thought this was a well known fact, I shall phrase it more carefully. 50% of the variation in measurable behavioural traits is accounted for by genetic variation (on average, it varies among traits). Here a measurable behavioural trait can be almost anything you can think of a way to measure: e.g. extroversion/introversion, thrill seeking behaviour, addictive behaviour, hours of television watched a day, number of sexual partners or speed while driving.Note that this isn't a theoretical claim about how genetics influences behaviour; it's an empirical claim about the observable facts of how genetics and behaviour interact. It's also absurd to claim that this is genetic determinism: it can't be - in order to be determinism you'd have to 100% genetic influence; that's not the case. This is a nice story, and I'm glad your parents took such an interest in you. But the evidence suggests that the current vogue for assigning intellectual development to "enriched environments" is simply wrong. It's based both on the notion of a "development window" which has never had any support (excepting specific areas of development such as hearing and vision) and misinterpretation of experiments that show that children tend to be like their parents (a fact far better explained by genetics than any environmental differences).There are two strong pieces of evidence that point this way: the first is that adoptive children of the same age and sex adopted at the same time are no more similar in intelligence than random strangers. The second is that the correlation between genetics and IQ actually increases as you grow older not decreases.On to Holmes: I don't have any to hand but I will attempt to locate some for you over the weekend. All of the results I have mentioned so far can be found in The Blank Slate by Stephen Pinker, which does include an extensive set of references.But you might be interested by a short read I located: The three laws of behavioural geneticsYes, this is the popular assumption. The trouble is that the evidence strongly suggests it's not true. While humans (and other higher animals) undoubtably do have much greater abilities to learn and adapt to their environments, these abilities are guided by instinct - the way in which we learn is, itself, instinctual and underneath the learning layers we are still strongly instinct driven.Have a look over Brown's list of human universals and observe how many seemingly higher behavours have emerged in every human culture from thumb sucking to rape and incest adversion. Then there's Chomskian universal grammar and the nature of language acquisition. Then there's the genetic causes of homosexual behaviour that I've seen you refer to before. I also refer you once again to the 50% genetics result that has been repeated so often.If you think about, the notion that human behaviour is entirely learned and does not involve genetics is absurd. Do you really think that you learned to have the same set of emotions as everyone around you? That you learned to be sexually aroused by breasts? That you learned that sexual arousal should cause an erection? That every mother needs to learn to love her child? That every single language on earth uses the same set of categories to divide up the world by chance? It's just not credible.This message has been edited by Mr Jack, 06-17-2005 06:51 AMThis message has been edited by Mr Jack, 06-21-2005 04:41 AM

I've corrected the URLs, thanks RAZD. Oddly, I'm sure I tested them in Preview and they worked. Sorry about that. If you find that list awkward, it is listed elsewhere:http://uwstudentweb.uwyo.edu/F/FENNERJ/TraitList.html
http://www.robotwisdom.com/ai/universals.htmlAs for the specifity of it, that's important. The broader the categories the less meaningful the list is; the importance of the list comes from the fact that you can find really quite specific features in all human cultures, an it is this specificity that points to a biological explanation. Well, no-ones really quite sure. A small % is probably accounted for by the shared environment (family) although many experiments designed to test this have found no correlation at all, some have found a small (<10%) correlation. One suggestion is that much, or most, of the other part (refered to as the 'unique environment') results from the influence of peer groups - as outline in The Nurture Assumption by Judith Rich Harris. I don't know of any research that has been done to test this hypothesis.Conscious thought isn't really an option, for two reasons:Firstly, thought is no less conscious because it's shaped by genetic infuence; in fact, what we are seeking to do is explain the behaviour of conscious thinkers so invoking conscious thought as part of the explanation is circular.Secondly, there is a growing body of evidence that conscious thought doesn't actually do much in the way of decision making, but instead acts to post-rationalise decisions already made subconsciously and, perhaps, act to stop actions.I'm not sure what you mean by a 'bell curve type effect'?

I disagree with Turkheimer on some details, but the most part it entirely supports my position. All evolutionary psychology needs to be valid is that behaviour be heriditary, and that heriditary component be significant - which is exactly what the first two laws grant. I entirely agree with Dr. Turkheimer on this.I suspect Dr. Turkheimer is actually refering to The Nurture Assumption rather than Pinker's works when he talks of books claiming no family involvemenr - but since we can't know for sure, it's pretty pointless to speculate. I find Turkheimer's position on this odd - it's certainly not supported by any evidence. Essentially what he's arguing is that "unique environment" (or more accurately the bit we can't assign to anything - it could be literally random rather than environmental, for example) or a goodly part of it is down to the family but in a way that effects every child differently.I find this an extrordinary hypothesis because it would mean that the way that a family affects a child in unique ways (even gentically identical children) is far more significant than the way it affects the child in a shared way - so that the difference in environmental effect between being two children in a christian fundementalist household in texas is bigger than the difference between being a child in that household and a child in a liberal household in new york. That strikes me as desperately unlikely. I have not read Brown's book or the research on which it is based, and with any such research it is likely that out of a list of two hundred there would be one or two errors. I sincerely doubt you claim that you could easily spot couple of non-universals however. Please do elaborate. My apologies. I agree with your position, although I would probably assign more to the genetics than you.I will respond to your previously posted critique later in another post, and search out some references for you.I'd like to be clear before we continue this discussion on what exactly it is that you are objecting to - this is my position:1. Human behaviour has a significant genetic component.
2. Given that human behaviour has a significant genetic component it will have been acted on and shaped by natural selection during the course of human evolution.
3. Given 1 & 2, it makes sense to approach human behaviour using the same tools as have been successfully employed to study animal behaviour by looking at their evolutionary history.
4. That is what Evolutionary Psychology means.Could you identify where your position differs from mine?

Would you mind giving examples of where these universals don't occur rather than simply asserting it?

This is a response to the critique posted hereThe role of body weight, waist-to-hip ratio, and breast size in judgments of female attractiveness.I am unsure why this paper had been chosen since it doesn't test, or claim to test, any evolutionary psychological claim. And, to make a more important point, even if it did and was flawed that would simply show that this paper is flawed and not that evolutionary psychology itself is flawed. Quite frankly this strikes me as pure projection. The paper begins with a historical retrospective and your starting comment strikes me as saying more about your bug-bear about the interaction between psychology, athropology and sociology. Yes, that is the assumption being made - but that's how hypothesis are made. You make an assumption (or guess) about how something is going to work and then look to see where that hypothesis would lead and perform experiments to test it. The experiment in this paper doesn't, in fact, do that. You complain that it has no functional significance and then go right on and explain it in functional terms.The study (and the study it references) attempts to find functional significance in the observed signals of sexual fitness because that is the approach you would take in animals. It's widely accepted in studies of animal behaviour that sexual signalling, and full blown sexual selection, are based on indicators of genetic fitness. Attempting to apply the same criteria to humans and seeing what happens is good science. Your proposed alternative is still an evolutionary psychological explanation. Why should whr be used as a such a signal? What evolutionary pressure is there to produce such a signal? You explanation may be simpler but what is the reason behind it's adoption? That's an entirely valid objection. However the article does cite several studies that do indicate differences in reproductive success of women with the desired whr w.r.t women with higher or lower whrs, these studies do provide a clear case supporting the authors interpretation. You correctly note that no proper analysis is done of whether these differences in reproductive success are sufficent to account for the sexual preferences. The study cannot. But the study makes no claim as to having done so. I actually find it a rather bizarre article, the initial discussion and the actual experiment are oddly disconnected. The experiment seems valid but it's such a tiny result that I struggle to see it's relevance. I'm guessing this is because in usual style they got their participants by posting for volunteers in the psychology department and psychology has a majority female population at undergraduate level.I agree with your criticisms of the study's methodology however I don't think the criticisms undermine the validity of the result but could suggest further research. The problem, of course, is that it's impossible to seperate the various factors involved in beauty when using real women without very large scale studies and statistical analysis. This study seeks to seperate out the factor by using line drawings - which will inevitably have the problems you outline. Evolutionary psychology does not deny the influence of cultural effects, it merely claims that genetics has a significant effect. c.f. imprinting studies with snow geese. It is irrelevant what primitive man did or didn't know; just as it doesn't matter whether a female bower bird understands the relevance of skills used to build a bower. Evolution does not operate by conscious knowledge. The experiment performed neither tests, nor answers, these questions. But nowhere in the conclusions does it claim to have done so.In summary then:I'm unclear as to why you picked this particular study; although the discussion is sociobiological in nature, the experiment does nothing to test whether the whr factors are cultural or genetic in nature and doesn't claim to have done so. It's also unfair to expect the study to do so; I don't expect every study of sub-atomic particles to justify QM, you shouldn't expect every study of human behaviour to justify sociobiology.Some of your objections are valid - however in many cases where you have offered alternatives they are, themselves, evolutionary in nature so how it's relevant to our dicussion of the validity of evolutionary psychology is beyond me.

You misunderstand me, I wasn't arguing against you; I was asking for examples so that we can discuss it.Rather than deal with part of the discussion of human universals here, and part in the reply to your other post I will bring all your comments into this post and respond to them here. Donald E. Brown (who created the list) is a Professor of Anthropology at the University of California, Santa Barbara not a Psychologist. I have not read his book, but took the list from Pinker's book. As I understand it Brown himself constructed the list primarily by studying the work of other anthropologists - principally George Murdock's HRAF files. He freely admits that under we cannot currently prove any particular universal, but presents his list as the best he can find from the (extensive) data he has studied. If you are interested you can find a fairly long review of his book here. The statement 'universal' refers to culture, 'normally' to individuals within this culture. It is not contradictory to claim both. For example, it is normal in our culture for children to be raised by their biological mother - but that doesn't mean their aren't raised by just their biological father, or their grandparents or people wholy unrelated to them. But that isn't what happens, Holmes, people don't wait until the breasts stop making milk and then start feeding the baby solids. Because the way in which people classify things is significant. There are as many different ways of classifying things as there are stars in the sky. How exactly people classify things is important, as are the differences between how people treat things in different categories. For example, Pinker reports on a peice of research performed on pre-school children in which the researchers described a process by which a racoon was converted into a skunk (by painting it, adding scent glands, etc) and asked the children whether it was a skunk or a racoon afterwards; the children respond it was still a racoon but when the researcher repeated the experiment but described a car being turned into a bird feeder they said it was a bird feeder afterwards.I think it's also important to distinguish between the list itself and any inference drawn from it. Whether or not it is significant that every culture categorises body parts is a very different question to whether every culture does, in fact, categorise body parts. I have no idea where you get this idea from, I can't see how it follows at all. Neither I, Pinker nor Brown has ever claimed that there isn't culture, that the environment doesn't have an effect or any other similar kind of absurd genetic determinism. You are attacking a straw man.Once again, I'm baffled by your stance. Genes are not limited to simply troting out a single effect, they're capable of producing subtle, complex behaviours that are triggered by complicated or rare situations or informed and structured by the environment. A simple example from animal behaviour is the various kinds of imprinting that occur in animals. For example, Snow Geese occur in blue and white varieties and white individuals prefer other white individuals as mates and vice-versa¹. This preference occurs through imprinting as can be demonstrated by experiments involving swaping eggs around or dying the parents (and subsequent mate choices) various colours. Imprinting is a non-trivial behaviour, here guided by the environment but I can't see anyone suggesting it's not a genetic process. I'm familiar with the Aztecs, Feudal Japan and moderately familiar with the Spartans - all three had proscriptions against murder, but with different concepts of who it's ok to kill - so you're quite right that murder is a social construct and that different cultures have different concepts of who it's OK to kill; as do we. I believe what is being claimed as universal is that every culture has people who it's not ok to kill and this is what Brown means by murder. I assume by 'cooking' he means to prepare with heat.Once again: the list is simply a list, the deduction from it a different matter. Things are on the list because everyone does them not because it is being argued they are genetic. In this case the drives that lead people to cook are genetic in origin: drive to eat, and the kinds of food we find tasty - the kind of food we eat is cultural as is the kind of food we won't. No-one is going to claim there's a specific gene, or set of genes for cooking because that's absurd but the complex interplay of our drives and our (strongly inheritable) intelligence. As you say: So that would be tabooed foods and food preferences then? Flatly, I don't believe you. Let me ask you a simple question: is it ok for me to rape someone? If you answer 'no' you've made a moral judgement. Yes, most cultures don't use the same system that we do, but they most certainly have a concept of morals and virtue, one particular striking example being Feudal Japan which elevated it's principles of honour far above the well being of the individual.¹Interestingly, a similar effect seems to occur in humans; individuals prefer others with similar body shapes to their own (e.g. europeans prefer the more rounded breats of european women to the more conical breasts of african women, africans preference goes the other way) - although I know of no studies done to test the hypothesis that this is an imprinting effect.