Picture: Sexual Psychology (summarized)

An evolutionary psychology blog (worth reading)

Two years ago I was excited by the launch of the first blog by a major evolutionary psychologist - Satoshi Kanazawa's The Scientific Fundamentalist. Unfortunately, it turned out Kanazawa is batshit insane and often face-palmingly wrong, so my search for a blog by a reasonable evolutionary psychologist continued. Luckily, a while back the interwebs provided: Rob Kurzban's ingeniously entitled Evolutionary Psychology Blog hosted by the equally ingeniously entitled journal Evolutionary Psychology. Being twice shy and all that, I didn't want to recommend Kurzban's blog before I gave it a good long look. Now that I have, I can say Kurzban's blog is well worth reading.

So... check it out.

Lazy Linking

"This is a news website article about a scientific finding"

• Martin Robbins' absolutely wonderful parody of bad science reporting. I really can't recommend it enough. 
• Also: read the superb comments (well, some of them at least - there are over 500). 

"An Ode to the Many Evolved Virtues of Human Semen"

• Jesse Bering on the psychological effects of semen (mostly on women). He covers tons of fascinating research, including the finding that semen may have an anti-depressant effect. (Though, as this comment points out, there is a serious confound). 
• Best line: “I’m not a medical doctor, but my testicles are licensed pharmaceutical suppliers”. (Said in jest, by the way). 

"There Is No Such Thing As Sexual Intercourse" 

• Anthropologist Pascal Boyer pwns lefty/po-mo academics. 

"U.S. Religious Knowledge Survey"

• Pew surveys Americans about their knowledge of religion. Shocking ignorance found. (You can take a quiz featuring some of the questions in the survey. FWIW, I got 13 out of 15...)
• Amazingly, only 85% of the respondents knew that an atheist is a person who doesn't believe in God. A finding consistent with the existence of 'atheists' who believe in God. (Yes, that is a contradiction in terms, but there you go).

"I was wrong about veganism. Let them eat meat – but farm it properly"

• I'm not linking to this for the content, but for George Monboit's wonderful demonstration that there is honor in saying "I was wrong". I've never been a fan of Monboit's, but his willingness to write this column certainly sways my opinion more to the positive side. 

"Should science journalists take sides?"

• Yes, says Ed Yong. They should (do their best to) side with truth. 

"Power Leads Us to Dehumanize Others"

• BPS Research Digest reviews research that vindicates Lord Acton. (Not that there was much doubt to begin with). 

"Ratzinger is an Enemy of Humanity"

• Richard Dawkins brilliantly responds to the Pope's deeply idiotic comment comparing atheists to Nazis. Read it. 

"Confirmation Bias in Science: How to Avoid It"

• Excellent piece at Ars Technica by Chris Lee on the evils of confirmation bias - our tendency to see only what we expect to see. Lee looks at the topic through the lens of various scientific controversies, including Jacques Benveniste's 'water memory' nonsense. 

"'Science Cop' Mugged"

• China's answer to Ben Goldacre, Fang Shimin, gets beaten up and threatened, apparently by plagiarists and/or charlatans who stand to lose from being exposed. Shocking. 

"Religion causes a chronic biasing of visual attention"

• Another fascinating study covered by BPS Research Digest.
• The researchers compared 'global' vs. 'local' thinking among "Dutch Conservative Calvinists (a form of Protestantism), Liberal Calvinists (who aren't so strict), Conservative Calvinists turned atheist and life-long atheists." 
• The results were surprising: "the life-long atheists showed the strongest bias for the big picture, followed by the Liberal Calvinists, and then the Conservative Calvinists and the former Conservative Calvinists turned atheist. The latter two groups performed similarly suggesting that more than seven years without religious practice wasn't enough to remove the effects of the religion on a person's attentional mindset."

Heh / LOL / Wow

"The Real Stuff White People Like"

• Absolutely fascinating analysis of 526,000 OkCupid profiles reveals the differences in tastes between White, Black and Asian males and females. 
• The sample is unlikely to be representative, but it's interesting nonetheless. 

"The Data So Far"

• Classic xkcd... (For xkcd n00bs: read the mouse-over text).

"2010 Astronomy Photographer of the Year"

• Astronomy porn at its finest. #7 and #11 are especially good.

"The Future of the Universe"

• ...as an animated GIF. 

"Orations of a Pre-Post Colonial Oompa Loompa to His Revolutionary Brothers-in-Arms"

• Need I say more?

Video: Tooby & Cosmides

Reason.tv (a project of Reason.com, a prominent libertarian publication) has an extended interview (embedded below, or click here) with Leda Cosmides and John Tooby, two of the founders of evolutionary psychology. There are all sorts of interesting tidbits and it serves as quite a good introduction to the field. It might do some of the more extreme critics of evolutionary psychology some good to see what actual (and responsible) scholars in the field think.

One thing: I can't say I was a fan of Cosmides and Tooby's foray into economics. The video can still be enjoyed, though.

A decidedly weird response

I forgot to mention the rather weird response David Spurrett and I received from the authors of the WEIRD paper I reported on the other day. For those of you who missed it, David and I basically agreed with Henrich et. al. (pdf) that Western undergraduates are often extreme outliers (i.e. weird), and that it is therefore extremely problematic that the behavioral science literature has relied so heavily on this group. Or, as we put it in our abstract: a literature focused on outliers is flawed. We went on to argue, though, that Henrich and his colleagues missed another big problem: most behavioral scientists are themselves deeply WEIRD - likely even weirder than their subjects.

As usual for Behavioral & Brain Sciences, the authors responded to all the open peer-commentaries, including ours. Here is what Henrich and co had to say about our piece (the weird bit in bold):

Finally, Meadon & Spurrett suggest that one important way of addressing these challenges is to bring more non-WEIRD researchers into the process. Empirical findings should be peer reviewed by researchers who bring different cultural models and implicit expectations to the problem. We agree with all these suggestions: Researchers can view phenomena from a novel perspective, not constrained by their own intuitions, when they study those from other cultures, and can potentially discover phenomena that they otherwise would not see. However, we disagree with an extreme version of this argument, which proposes that researchers should entirely avoid studying people from their own culture. Researcher’s intuitions about the ways people in their own cultures think can be a useful source of understanding in building theories and in honing research instruments. 

Well.... sure. But David and I never suggested anything of the kind, and it's not an idea either of us has ever taken seriously. Indeed, that researchers have some advantages when studying their own cultures was part of our point. There are excellent reasons to think diverse research communities are better, so one reason additional non-WEIRD researchers would be useful is that they often have different biases, so they may spot hidden assumptions, value judgments masquerading as facts or other problems that WEIRD researchers may miss. A Nepalese psychologist peer-reviewing a German study - even on German subjects - may see something someone as WEIRD as a German researcher overlooked, for example. But, equally importantly, a Nepalese researcher often has different knowledge like hard-to-learn cultural sensitivity, in-depth knowledge of both a local language and academic English (vital for accurate translation), or an understanding of some important nuance. So, yes, people studying their own cultures "can be a useful source of understanding in building theories and in honing research instruments". That was part of our point.

Anyway, the rest of Henrich et. al.'s response to our commentary, in which they make several excellent points:

More non-WEIRD researchers should be brought into the discussion, as well as onto collaborative research teams. Research teams themselves that better reflect broad global diversity can more effectively address the challenges delineated by Fessler, Rochat, and Bennis. [other commentators on the paper]. With regard to these points, it is instructive to consider why psychology is more dominated by American research than any other science (May 1997). One possibility is that pursuing a career in psychology is a luxury that people cannot afford until the countries and societies in which they live have achieved sufficient economic evelopment. This may be part of the explanation, although this would not explain why universities in wealthy societies like those of Japan and Western Europe typically have proportionately smaller complements of psychology researchers and majors than do North American universities. Another possibility, which we highlight here, is that the field’s emphasis on WEIRD samples, coupled with the guiding assumption of universal psychological processes, tends to unintentionally marginalize international research. If non-WEIRD researchers are interested in extending findings initially established with WEIRD samples in their home populations, such as findings associated with motivations for self-enhancement, they may well be unable to replicate the American results. The implicit assumption that self-enhancement motivations are similar everywhere would suggest that such failed replications are not due to the nature of the samples studied but instead due to some kind of unspecified deficiency in the methods of the non-WEIRD researchers. American researchers have a distinct advantage in that the field’s key theories were largely constructed on data from American participants, and we suggest that this is likely why American research constitutes 70% of the field’s citations. International research suffers from the disadvantage of trying to extend American-based theories with participants who often have different psychological tendencies, yielding results that are difficult to interpret while embracing an untested assumption of universal psychological processes. In contrast, if the field comes to recognize that psychological phenomena cannot be assumed to be universal until demonstrated as such, then research conducted by non-WEIRD researchers, guided by non-WEIRD intuitions, and studied with non-WEIRD samples, would come to be viewed as particularly important for understanding human psychology.

For more discussion, see the comments on my WEIRD post over on Google Buzz, featuring contributions by David, yours truly and the most excellent Simon Halliday.

Are most experimental subjects in behavioral science WEIRD?

Note: here is a follow up post.

My supervisor David Spurrett and I have a commentary on an important paper - "The weirdest people in the world?" (pdf) - in the most recent edition of Behavioral & Brain Sciences. The authors of the paper, Canadian psychologists Joseph Henrich, Steven Heine and Ara Norenzayan, argue that most experimental subjects in the behavioral sciences are WEIRD - Western, Educated, Industrialized, Rich, and Democratic - and thus weird - not representative of most human beings. And this, if true, is a very serious problem indeed. Behavioral scientists (anthropologists, psychologists, behavioral economists and so on) are often interested in explaining the brains, minds and behavior of Homo sapiens as a species. (Some scientists, of course, are only interested in understanding specific cultures or what makes us different, but one important goal of the behavioral sciences has long been to explain universal human behavior). As evolutionary psychologists John Tooby and Leda Cosmides have put it, they "seek to characterize the universal, species-typical architecture of [the information-processing mechanisms that generate behavior]".

But... Henrich and his colleagues review a large body of literature that seems to show that, across several domains, Western undergraduates - the workhorses of the behavioral sciences - are extreme outliers. In other words, if they are correct, most of the data behavioral scientists have used to test hypothesis and to drive theorizing derives from subjects who are possibly the least suited for generalizing about the human race. Take as an example the Müller-Lyer illusion. In the diagram below, the lines labeled "a" and "b" are exactly equal in length, but many subjects perceive "b" as longer than "a".

This finding (which goes back all the way to 1889) has been used to make deductions about how the human visual system works. The Wikipedia article on the illusion, for example, states that one possible explanation for the effect is that "the visual system processes that judge depth and distance assume in general that the 'angles in' configuration corresponds to an object which is closer, and the 'angles out' configuration corresponds to an object which is far away". Plausible enough. Except that for some people - San foragers, for example - the illusion does not exist, and in many other non-WEIRD societies the effect size is significantly smaller. Henrich and his colleagues cite the work of Segall et. al. (1966), who worked out the magnitude of the illusion across 16 societies by varying the relative lengths of "a" and "b" and then asking subjects to indicate when they thought the lines were equal. The percentage by which "a" must be longer than "b" before the lines are adjudged equal - what they call the "point of subjective equality" (PSE) - varies substantially between subjects from different cultures - and, importantly, WEIRD-subjects are extreme outliers. The results are summarized in the following graph:

Both WEIRD adults and children (aged 5-11) require "a" to be 18%+ longer than "b" before they're perceived as equal, but for the San and South African miners, the illusion simply does not exist - their PSEs are not statistically distinguishable from 0. Why this difference arises is unknown, but Segall et. al. claim it is due to WEIRD people's visual systems developing differently because modern environments expose them to ("unnatural") shapes like 'carpeted corners', thus calibrating their visual systems in a way that favors the emergence of the illusion. Whatever the true explanation, however, it is clear that it is not permissible to use the existence of the illusion among WEIRD subjects to make inferences about the visual system. This is especially true since the San subjects were hunter-gatherers, just like all people for the vast majority of human evolutionary history. Given that species-typical features of the visual system would have evolved in this period, it is particularly telling that PSE seems to be positively correlated with the 'modernity' of the societies in question. (Warning: this is an "eyeball" observation; I haven't done a proper statistical analysis. Caveat emptor).

This is one example from an extremely long paper, but it conveys a flavor of the kind of evidence the authors present. (For much more, see "We agree it's WEIRD, but is it WEIRD enough?" over at Neuroanthropology). Having read the article very carefully, and despite some concerns, I think Henrich, Heine and Norenzayan are right: the Western undergraduate is often unrepresentative of humanity, and the behavioral science literature needs a lot of fixing as a result. (Most obviously, we need far more large, highly-powered, globally representative, prospectively designed, cross-cultural studies). Serious as this is, unfortunately, it gets worse... Since David and I worked extremely hard to present our argument clearly and concisely in our commentary (pdf - our piece starts on p. 44 of the pdf, paginated by BBS as p. 104), and I doubt I could improve on it, what follows is a slightly edited - simplified and somewhat de-academicized - version of the meat of our argument. (Note: each issue of BBS consists of a "target article" - in this case, Henrich et. al. - and 20 or so short peer-commentaries).

Henrich et al. underplay – to the point of missing – that how the behavioural sciences research community itself is constituted introduces biases. That the subject-pool of behavioural science is so shallow is indeed a serious problem, but so is the fact that the majority of behavioural researchers are themselves deeply WEIRD. People in Western countries have, on average, a remarkably homogeneous set of values compared to the full range of worldwide variability (Inglehart & Welzel 2005), and the data Henrich and his colleagues present suggest similarly population-level homogeneity in cognitive styles. Moreover, academics are more uniform than the populations from which they are drawn, so it is likely behavioral scientists are even WEIRDer than their most common subjects. Henrich and his colleagues review a bunch of studies and experiments that did not strike those who designed and conducted them as focused on outliers. Intelligent scientists acting in good faith conducted, peer-reviewed, and published this research, in many cases honestly believing that it threw light on human nature. This forcefully illustrates the power of the biases on the part of researchers themselves. It also suggests that, besides widening the pool of subjects, there are significant gains to be made by broadening the range of inputs to the scientific process, including in the conception, design, and evaluation of empirical and theoretical work. Given that diverse groups are demonstrably better at some kinds of problem solving, as things stand, the WEIRD-dominated literature is robbed of potentially worthwhile perspectives, critiques, and hypotheses that a truly global research community could provide. Clearly, simply increasing the number of behavioural sciences researchers will, in general, be beneficial. Our key contention, though, is that the marginal benefits of additional Western researchers are much smaller than the marginal benefits of more non-Western researchers, among other things, just because they are non-Western.

The non-Western world, in short, can contribute not only additional subjects to experiment upon – the main focus of the target article’s recommendations – but also additional researchers, with novel perspectives and ideas and who are less affected by WEIRD biases. (Naturally, these researchers will have biases of their own. Our claim is not that there is someone who consistently knows better; it is that diverse groups of investigators can avoid some kinds of error.) Clearly, these researchers will have to be educated, will likely be middle class, and, since science flourishes in politically open societies, they will tend be concentrated in liberal countries. Nevertheless, additional non-Western researchers, even if they are educated and relatively wealthy, could be a boon to the behavioural sciences.

A direct and powerful way to remedy both sources of bias – too many WEIRD subjects and too few non-WEIRD researchers – is to foster research capacity in the non-Western world. Non-WEIRD researchers tend to study non-WEIRD subjects, so increasing their number will deepen the subject pool and widen the range of inputs to the scientific process at the same time. Building research capacity, however, should not merely involve collaborations led by WEIRD researchers; it should aim to generate studies led and initiated by non-Western researchers. Committed and long-term inter-institutional collaboration between Western and non-Western universities focused on remedying the deficits in the behavioral sciences literature should include internships at Western universities for non-Western researchers, stints at non-Western universities for WEIRD researchers, and extensive student exchange programs (especially for graduate students). Unlike many existing scholarship and exchange programs in the sciences, a key point of the necessary programs should be for the learning to proceed in both directions.

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Henrich, J., Heine, S., & Norenzayan, A. (2010). The weirdest people in the world? Behavioral and Brain Sciences, 33 (2-3), 61-83 DOI: 10.1017/S0140525X0999152X

Meadon, M., & Spurrett, D. (2010). It's not just the subjects – there are too many WEIRD researchers Behavioral and Brain Sciences, 33 (2-3), 104-105 DOI: 10.1017/S0140525X10000208

Depictions of violence in rock art

A street fight, via Wikipedia.

To understand the phenomena of murder, war, genocide, and other forms of human intraspecific violence, we need to know whether to invoke evolutionary biological explanations or restrict ourselves primarily to socio-cultural theories. If the incidence of violent conflict was high and recurrent for a substantial period during human evolution, and given that being killed drastically reduced fitness and killing may have increased it, then strong selective pressures would have favored physical and psychological adaptations to violence. Conversely, if interpersonal violence was rare or nonexistent until much more recently – until the rise of agriculture about 10,000 years ago, say – not enough time would have elapsed for natural selection to have forged significant new adaptations, and socio-cultural explanations of violence would thus predominate. (It should be noted, though, that recent human evolution has been very rapid, so this judgement may have to be revised in future as more evidence comes in). More precisely, whether adaptations to violence exist or not depends on the intensity of the selection pressures and their duration, and the intensity of the selection pressures is in turn a function of the frequency of violence and the magnitude of its impact on fitness. Thus, to determine the plausibility of positing traits that are adaptations to violence we need to know: (1) how frequent violence was, (2) whether it was recurrent in human evolutionary history and (3) how large its impact on inclusive fitness was.

Determining (3), of course, depends in part on the values we assign to (1) and (2). Being killed before reproduction obviously reduced fitness to zero, and being killed after reproduction eliminated all the kin altruism the individual would otherwise have engaged in. The impact on fitness of being injured depended on the severity of the injury, but it seems clear it would have been negative and serious. What we need to deduce the magnitude of (3) over human evolutionary history, then, is sound empirical estimates of (1) and (2). Unfortunately, however, these estimates are extremely difficult to make because the available evidence is sparse and often ambiguous. Broadly speaking, there are two lines of evidence available to us: studies of contemporary hunter-gatherers and the paleoanthropological and archeological record. There are several controversies around both lines of evidence, but for this post I'll focus on one type of evidence from the archeological record: depictions of violence in rock art.

A beautiful example of such a depiction is a San pictograph "Veg 'n Vlug" (Afrikaans: "Fight or Flight") that is near Clanwilliam in the Cederberg of South Africa. (Note: I've used the Auto-Level feature in Paint.NET to bring out some of the details):

John Parkington describes (large pdf; pp. 62 - 65) the scene thus:

The fight element is created by painting around a small recess in the rock surface to give the impression of a small cave from which a group of humans peer, one of them shooting arrows. A second group of humans, arranged as a procession and depicted apparently moving along a pair of red lines, face the cave occupants and also shoot arrows. From the ‘cave’ several people, most of them male, flee along more pairs of red parallel lines. One human figure, clearly lying prone is connected by these same lines to a strange seated  figure holding the end of the lines, neither of them directly connected with the cave itself. From the neck of the strange seated figure a single red line leads to another small figure with upraised arms.

Contrary to the hypothesis - favored by neo-Rousseauians like Brian Ferguson - that human evolutionary history was entirely (or largely) peaceful, then, we have at least an existence proof of such violence. Or do we? Ferguson has argued that pictographs seemingly depicting violence should not be interpreted literally, but rather metaphorically. In other words, "Veg 'n Vlug" doesn't depict an actual event, the artists meant something else entirely, or is perhaps an attempt at sympathetic magic. (To be clear, as far as I know Ferguson has never written about this specific pictograph. I'm illustrating the kind of argument he's made about other rock art depictions of violence). And there are certainly aspects of "Veg 'n Vlug" that isn't literal. Parkington continues from the above quotation:

This bald, but reasonably literal description gives no hint of the intriguing and enigmatic details that impart a deeper, but still obscure meaning to this apparently unified composition. Take the double red lines for example. They cannot, as might appear at first glance, be footprints or a path, because they connect the feet of those in the procession to the bow of one of the cave occupants and emerge from the bowstring to enter the mouth (or face) of the bow and arrow-wielding figure. The strange figure reeling in the lines from the feet of the prone, perhaps dead, figure cannot be manipulating footprints or a path in any literal way. It is likely that the double, parallel red lines are painted to illustrate some connectedness between people that is intangible but central to the meaning of the composition. The attachments to feet, hands, equipment and mouth probably indicate the nature of the connection but are not explicit enough to provide a definitive narrative.

So what does this mean? Well, clearly, the pictograph cannot be strictly literal. Perhaps the artist(s) intended to convey some, now obscure, metaphorical meaning. Perhaps aspects of the drawing represent something abstract. Contra Ferguson et. al., though, I don't think it is reasonable to conclude that a metaphorical interpretation obviates a literal interpretation.

Take my avatar and favorite painting, A Philosopher Lecturing on the Orrery by Joseph Wright:

The painting has two, complementary, meanings. Whether Wright had in mind a specific instance of a scientist^[1] demonstrating an orrery (a clockwork-driven model of the universe), it's clearly the kind of thing that went on at the time. That is, there certainly were orreries, scientists, and scientists demonstrating orreries and the painting represents an instance of the latter. The painting conveys much more than just 'such-and-such' happened, though. Many metaphorical interpretations are possible, naturally, but Wright seems to have intended it as a celebration of science, of the Enlightenment. The point could be argued, but suppose we agree A Philosopher represents the Enlightenment. Does that mean we have to abandon a literal reading? Insist that the painting tells us nothing about orreries and scientists? Obviously not. Literal and metaphorical representations can, and often do, co-exist.

What this illustrates, I'm suggesting, is that however we interpret the non-literal aspects of "Veg 'n Vlug", we need not abandon a literal reading. In other words, even if there are abstract or metaphorical meanings we can assign to the pictograph, it still depicts two groups engaging in violence. It's necessary to go a step or two further, in fact. Not only can metaphorical and literal readings co-exist, we should apply Occam's Razor and favor a kind of interpretive parsimony: the simplest interpretation - the one that requires the fewest new assumptions - is likely the correct one. And in nearly all cases, the literal interpretation is the simplest.

Whatever metaphorical or abstract readings we assign to any pictograph do not necessarily obviate literal interpretations. And interpretive parsimony - favoring the simplest possible interpretation - cautions against metaphorical readings in the first place, and demands especially strong evidence before we elevate metaphor over straightforward representation. In short, unless we have strong reasons to think otherwise, pictographs like "Veg en Vlug" represent evidence of ancient violence.

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^[1] The word 'philosopher' at the time had multiple meanings, one of which was what we would now call a scientist.

Adaptations for the visual assessment of formadibility: Part II

In Part I of this series, I summarized the experiments and findings of Aaron Sell and colleagues' paper "Human adaptations for the visual assessment of strength and fighting ability from the body and face". In Part II, I evaluate their claims.

The evidence Sell et. al. present seems compelling with regards to proposition (i): adults appear to be able to make remarkably accurate estimates of upper-body strength from even degraded cues such as static images of faces. As I noted in Part I, however, the truth of propositions (ii) (that this ability is an adaptation) and (iii) (that upper-body strength determines formidability) are more doubtful. I will assess the evidence for each of these claims, starting with the latter.

Adaptations for the visual assessment of formidability: Part I

In the last couple of years there has been an explosion in research on faces and what can be inferred from them. It turns out, for example, that you can predict electoral outcomes from rapid and unreflective facial judgments, that women can (partially) determine a man's level of interest in infants from his face alone, that the facial expression of fear enhances sensory acquisition, and much, much else. A particularly interesting addition to this literature is Aaron Sell and colleagues' paper, "Human adaptations for the visual assessment of strength and fighting ability from the body and face". Sell et. al. hypothesized that human beings possess evolved psychological mechanisms 'designed' to estimate the fighting ability (or physical formidability) of conspecifics - i.e. other Homo sapiens sapiens - from minimal visual information. An ancillary, but important, claim the authors also make is that formidability is largely a function of upper-body strength and thus the latter is a suitable proxy for the former. To summarize for clarity, Sell et. al. claim that: 

• (i) people can estimate the formidability of others from visual cues of their bodies and faces, 
• (ii) this ability is an adaptation, and thus evolved by natural selection, and
• (iii) upper-body strength is the single most important determining factor of fighting ability. 

The authors’ rationale for the first two hypotheses stems from the observation that in social species such as humans, ‘the magnitude of the costs an individual can inflict on competitors largely determines its negotiating position’ (p. 575). That is, formidability is often an important component of an organism’s ability to compete in zero-sum games (notably, access to limiting resources). Given the dangers of physical confrontation, a rapid visual assessment of the formidability of an opponent could be extremely beneficial because it would allow an individual to weigh up its chances of success, and thus choose to fight only when there is a reasonable prospect of victory. Indeed, Sell et. al. note that the widespread so-called ritualized animal contests are best interpreted as joint demonstrations and assessments of formidability, with physical violence usually ensuing only when individuals are closely matched. If the ability to visually estimate a competitor’s formidability was indeed adaptive, and if violence was frequent and recurrent throughout human evolutionary history (as is likely the case), it is not unreasonable to expect natural selection to have forged mechanisms to make such estimates. Sell and his colleagues tested hypothesis (i) empirically in a number of studies and the evidence seems to bear it out overall. While the truth of (ii) is more doubtful, I will argue that, pending further research, it is reasonable to accept it preliminarily for a number of reasons. Finally, I will argue the lack of empirical evidence in the study for (iii) is problematic but not decisively so: it is clear that there is a correlation between upper-body strength and formidability, but we do not know how strong this correlation is so it is difficult to judge how good a proxy the one is for the other.


After the jump, I summarize Sell et. al.'s primary findings (though I leave out one of their experiments). In Part II - coming later in the week - I evaluate their paper.

Gene Callahan vs Evolutionary Psychology

So I recently had an uncharacteristic (and unpleasant) online altercation with one Gene Callahan about evolutionary psychology and, amazingly, whether Daniel Dennett should be taken seriously. I'm not blogging about this because it is inherently interesting (it's not), but because it nicely illustrates several common misconceptions about applying evolution to psychology and it reminds us that intellectual arrogance is a Bad Thing.

(I’d like to note before proceeding that it’s not as if I’m an uncritical fan of evolutionary psychology. There are, I think, numerous problems in the field, and the standards of evidence is far too often far too low. Some papers in the field are downright embarrassing (this one is the worst I’ve come across) and on my blog I have, among other things, excoriated Satoshi Kanazawa and critiqued Shermer’s application of evolutionary psychology to markets.)

Anyway, the saga in question started when a friend shared a blog post of Callahan’s on Google Reader in which he endorses John Dupré’s Human Nature and the Limits of Science, an uninformed screed against evolutionary thinking in psychology. (See this critique). I won’t have that much to say about the content of Callahan’s post – I will focus on his replies to my comments – but one remark about it is in order. Callahan:

I’ve just been re-reading John Dupre’s wonderful take-down of evolutionary psychology, Human Nature and the Limits of Science. Now, Dupre never disputes the obvious truism that, say, human ethics or religion evolved. But he notes that this is remarkably uninformative, since everything humans do so (sic) evolved, including their ability to write papers on evolutionary psychology!

This is somewhat cryptic and unclear, but straightforwardly interpreted, it is obviously wrong. To see why, consider the following. (I) Phenotypic structures (more precisely, biological processes) are either adaptations or the by-products of adaptations. (II) What distinguishes evolutionary psychology (at least of the Santa Barbara School) from sociobiology is the claim (see Tooby & Cosmides, 1987 [pdf]) that manifest behavior doesn’t evolve, modular information processing systems embedded in brains do. (III) Behavior is the result of a complex interaction between the environment and these information-processing systems; including direct environmental influences (e.g. drugs, brain injury) on the physical substrate of these information-processors. Observed behavior, then, is the product of the environment interacting with information processing mechanisms in the brain, and the brain is constituted of adaptations – structures that exist just because they increased fitness relative to alternatives in evolutionary history, including by producing or facilitating certain behaviors – or the by-products of such adaptations. It is therefore false that ‘everything humans do evolved’ since behaviors themselves don’t evolve, some behaviors result from by-products of evolution (not to mention pathology), and rapidly changing environments (the appearance of development of civilization, say) can interact with evolved psychological traits to produce novel behaviors (including writing papers on evolutionary psychology). The proposition that evolutionary psychology – broadly construed – is uninformative stems from these misunderstandings, and is indistinguishable from the crazy idea that evolutionary thinking generally is uninformative. Moreover, this claim is belied by the fact that we have discovered psychological abilities and traits (e.g., e.g.) that we didn't know about until we thought about human psychology from an evolutionary perspective.

On to the actual altercation… Callahan’s post rather annoyed me, so I left an aggressive – probably too aggressive – comment to the effect that (a) he is unqualified to have an opinion and (b) that he should read Daniel Dennett’s critique of the book. On reflection, I regret making point (a) as baldly as I did: I failed to err on the side of charity and to assume good faith. (Not to mention that I took Wikipedia’s word that he’s an economist, when he self-identifies as a philosopher, though I can’t help pointing out that he has a PhD in neither, so appending “in-training” is appropriate. Note: I don’t have a PhD either, so I happily concede I’m a wannabe cognitive scientist, not the real deal... yet). Understandably, Callahan didn’t take too kindly to my comment, so he replied aggressively himself, and then headed over to my blog and threw insults around on two of my posts: here and here. (Some tangential pedagogy: as I explained at length in my Fun with Fallacies post a while back, there is a difference between the ad hominem logical fallacy and mere insult. Callahan [I think, the comment was anonymous] calling me a “rude little punk”, for example, is not an instance of the ad hominem logical fallacy; even saying ‘you’re wrong and a rude little punk’ wouldn’t be fallacious. Only if he had said (or implied) ‘you’re wrong because you’re a rude little punk’ would he have committed the fallacy. There must be some inference drawn from some purported negative quality for the fallacy to occur, merely alleging someone has a negative quality is not itself fallacious, though of course it may be false or libellous).

Anyway, Callahan’s reaction to (b) was remarkable and illustrative: he dismissed Dennett’s critique of Dupré without reading it because he thinks Dennett’s work is a “rubbish heap”. Here’s what he said:

“Oh, and I’m not going to bother reading his [Dennett's] criticisms of Dupre. If I read several things by someone and they are universally rubbish, I really can’t be bothered to keep going through the rubbish heap. Anyone dull enough to have come up with the ‘brights’ idea really can be dismissed out of hand, don’t you think?”

Wow. The first sentence is the most interesting, but note that the second is factually inaccurate (Dennett endorsed the Brights idea – as did Dawkins – but neither came up with it) and invalid to boot. Worse, the suppressed premise (pdf) that would make the argument valid - ‘anyone who has one really daft idea can be dismissed out of hand (on all topics)’ – is clearly false. Granting for argument’s sake that the Brights idea was daft, it’s simply not true that if someone has one spectacularly bad idea that everything else they say will be wrong. Newton had silly ideas about alchemy and the Bible, but that doesn’t mean we can dismiss the Principia. Linus Pauling obstinately stuck to the incredibly implausible notion that ultra-high doses of Vitamin C can cure cancer, but that doesn't mean his work in chemistry was worthless. Physicists with idiotic philosophical or religious views are a dime a dozen, but that doesn’t mean their work as physicists is necessarily bad. Is it really that surprising that a philosopher and a ethologist, respectively, could be persuaded to endorse a bad marketing idea? If they did so would it mean that their professional work was all worthless?

Callahan’s first point in the above paragraph, though, is far more interesting and so worth looking into in a bit more detail. At first I thought he couldn’t possibly believe it – that perhaps he was just pissed off and said something silly in the heat of the moment – but he failed to back down in subsequent comments, so he really does seem to believe it. In summary, his argument is: ‘I read x% of Dennett’s work, what I read was universally rubbish, therefore everything by Dennett is rubbish’. (Callahan calls Dennett's work 'a rubbish heap', so he's not just making the more reasonable claim that 'he couldn't be bothered to read more of it'). This argument too is invalid - though of course I hardly expect people to make consistently logically valid arguments in blog comments. The point is that it contains at least one false suppressed premise, namely: ‘if I’ve read some proportion of a scholar’s work, I can judge all of it.’ This is both arrogant and false, the latter since for it to be true everyone would have to produce either consistent rubbish or consistent non-rubbish: it implausibly rules out a mixed bag. Newton, again, produced utter nonsense and sublime science, Jared Diamond wrote both Guns, Germs, and Steel (one of the best books of the 90s is my opinion) and Why is Sex Fun? (which was very bad indeed) and so on.

As a rule of thumb, I’d say that unless (1) you have read a good proportion of some scholar’s output, (2) you are qualified to judge all of it, and unless (3) everything you have read is entirely devoid of merit and without any redeeming qualities whatsoever, making a black-and-white inference about an entire corpus of work is just not reasonable. (People who make a priori unlikely claims in conflict with scientific consensus, show no interest in justifying their claims, and who lack relevant expertise can in most cases be dismissed out of hand. Sylvia Brown’s books, for example, are just not worth paying attention to. I take it as obvious that Dennett does not come close to fulfilling these criteria). Given how much Dennett has produced I’m willing to bet Callahan has not satisfied (1), and I have serious doubts about (2) since as far as I know not even Callahan himself claims to be a qualified cognitive scientist or philosopher of mind. More importantly, the prior probability of (3) is preposterously low and Callahan thus has a huge burden of proof to discharge. For him to do so he would not only have to demonstrate (preferably in a mainstream peer-reviewed journal) that, say, Consciousness Explained (CE) and Darwin’s Dangerous Idea (DDI) are rubbish but also explain why so many smart people – whether they agree with Dennett or not – were fooled into concluding the opposite. In other words, he must rigorously justify his initial contention not only that Dennett is wrong, but so wrong that his work is entirely worthless. And, if Dennett’s work is indeed utter rubbish, Callahan must explain why Dennett has been so influential: why, for example, CE has been cited 4700+ times and DDI 3000+ times. (Callahan objected to this point by saying it merely shows Dennett is famous, and mere fame presumably doesn’t track genuine merit. I responded that there’s a distinction between fame and influence: Dennett is both, Paris Hilton is only the former, Frege (say) is only the latter, and both Callahan and I are neither. Scholars just don’t see the need to read, let alone refer or respond to, utter rubbish so either Callahan is wrong or thousands of highly trained and really intelligent people are deluded. Of course, Callahan could be right, but I wouldn't recommend betting on it).

The moral of the preceding analysis, I think, is that intellectual arrogance is a very Bad Thing. I admit that I’m not exactly diffident, and that I have regularly fallen afoul of the principles I outline below. But I’m not nearly arrogant enough to dismiss whole disciples or declare all of an influential and prolific academic’s work utter rubbish. The common cause of such extreme beliefs, it seems to me, is overweening intellectual self-confidence, which is in turn arguably a product of an insufficient familiarity with one’s own fallibility. Cognitive biases and illusions are universal and ineradicable, the world is incredibly complicated and you can know only a fraction of the currently knowable. The mark of someone familiar with the above is scepticism, suspicion of bald assertions and hasty generalization, doubt, caution, a willingness to reconsider and admit error, and being scrupulously careful with facts and arguments. Callahan, it seems to me, fails to live up to these principles and the result is beliefs that, frankly, are downright idiotic. Or, as I put it rather more colorfully in my comments on his post, if these really are his beliefs, he should STFU, GTFO and take his FAIL with him. Srsly.

Of course, I could be wrong. Maybe I've been blinded by emotion, maybe I've been unfair, maybe I've misunderstood. If so, show me I'm wrong and I'll reconsider. Really.

Fun with sex

One important factor that drove the evolution of psychological sexual dimorphism is the difference in the minimum obligatory parental investment between the sexes. (This is the great insight of Trivers, 1972). Men, as the rather coarse saying has it, ‘can leave a bed unmade’. That is, a man need only invest a few minutes of effort and some sperm to produce a child. Women, on the contrary, must invest as much as men plus 9 months of pregnancy and, given the absence of baby formula on the African savannah, several months or years of breast-feeding. Moreover, before the advent of modern medicine, childbirth was very dangerous so a woman quite literally risked her life to have children. The minimum obligatory investment for men and women, then, is radically different, so we should expect the evolution of a dimorphic sexual psychology reflecting, as Trivers put it, 'female choice and male competition'. (This is, obviously, a crude simplification). And, not surprisingly, we have a mountain of empirical evidence that confirms this expectation.

There is a lot one can say about this theory, and the above sketch certainly does not do it justice or acknowledge the complexities and uncertainties of the empirical data. But a story I saw in a newspaper recently made me think of one of its features, namely, that a man could always be doing better. From the perspective of a man’s genes, women are an extremely valuable and limiting resource. This may seem a bit weird, so let me explain. There are (of course) a finite number of fertile women alive at any given time, and, since a man has such a low minimum parental investment, he could, in principle, impregnate tens of thousands of them. Women, on the other hand, have to carry and give birth to all their offspring, so the total number of children each woman could have in a lifetime is severely limited by comparison. Men have the potential to sire several orders of magnitude more offspring than women, and as a result there is an oversupply of willing males. (One interesting consequence is that there is a much greater variance in male reproductive success, which produces much greater variance in males in a whole range of traits. The variance in male mathematics grades, for example, is substantially higher than that of women).

In any case, the story that got me thinking about this again concerns one Desmond Hatchett (pictured above). Hatchett, an American man from Tennessee, is only 29 years old but, amazingly, has fathered 20 children. Not quite Ismial the Bloodthirsty (who reportedly sired at least 888 children) or Genghis Khan (who is the likely ancestor [pdf] of ~8% of Central Asian men, and ~0.5% of all men worldwide), but evolutionary speaking, not bad at all.

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Trivers, R. (1972) "Parental investment and sexual selection" in Campbell, B. (ed.), Sexual Selection and the Descent of Man.

DS Wilson on Evolutionary Psychology and the media

David Sloan Wilson has a pretty interesting piece in the HuffPo about evolutionary psychology and its portrayal in the media. Wilson argues, among other things, that the study of human behavior from an evolutionary perspective is flourishing and rigorous, but that it is significantly more diverse than sometimes thought. Specifically, he says the term evolutionary psychology has become overly identified with the Tooby & Cosmides school of thought (the “Santa Barbara school”) which Wilson thinks is flawed in several respects. The meat:

How did the blueprint offered by Cosmides and Tooby go wrong? Let me count the ways: 1) They portrayed the mind as a collection of hundreds of special-purpose modules that evolved to solve specific problems in the EEA. 2) Their conception of the EEA was limited to the range of environments occupied by humans during their evolution as a species, which they acknowledged to be diverse. However, it did not stretch back in time to include primate, mammalian and vertebrate adaptations; nor did it stretch forward to include rapid genetic evolution since our hunter-gatherer existence. 3) They emphasized a universal human nature, or rather separate male and female natures, while minimizing the importance of adaptive genetic variation that cuts across both sexes. 4) They dismissed open-ended, domain-general psychological processes as a theoretical impossibility, creating a polarized worldview with "Evolutionary Psychology" at the positive end and "The Standard Social Science Model (SSSM)" at the negative end; 5) Their blueprint had almost nothing to say about culture as an open-ended evolutionary process that can adapt human populations to their current environments. They did not deny the possibility of transmitted culture, but they had almost nothing to say about it. Their most important point was that what seems like transmitted culture can instead be an expression of genetically programmed individual behavioral flexibility (evoked culture).

Ending on a more optimistic note:

Evolution is here to stay as a theory that can help us understand the human condition, along with the rest of the living world. With understanding comes the capacity for improvement. This is not just an idle intellectual pursuit but has consequences for the solution of real-world problems, so the sooner we can advance our understanding the better. One reason that we are just starting is because the term "evolution" became stigmatized early in the 20th century, in the same way that terms such as "sociobiology" and "evolutionary psychology" tend to become stigmatized today. This problem can be avoided by distinguishing particular schools of thought from the more general theory, so that the former can be accepted or rejected on their own merits without questioning the merits of the latter.

DNA & Dating

I blogged back in January about ScientificMatch, a dating service that, perhaps rather unromantically, matches people based on their genes. I see New Scientist magazine has caught on, and has published a great article about this rather odd development. The author of the piece, Linda Geddes, summarizes the scientific rationale for the service, delves into several of the criticisms thereof and, most interestingly, subjects herself and her fiancée to the testing. Good stuff indeed.

My bottom line, for what it's worth, is that it's plausible to think this kind of genetic matching is an improvement over sheer chance, but I doubt very much it'll be superior to our evolved sexual psychology. (Although I do suspect it'll in general predict compatibility better than questionnaire-based online matching services). So, if you're wealthy and lonely, give it a try... otherwise, stick to the singles bars.

Video: Brian Ferguson on war

Rutgers professor Brain Ferguson is one of the leading anthropologists of war and in the Bloggingheads.tv interview embedded below (or click here) he argues the evolutionary state of nature was not Hobbesian (i.e. warlike), but broadly Rousseauian (i.e. peaceful). To be clear, Ferguson does not deny that warfare exists worldwide, his position is that it emerged in the Mesolithic and that the Paleolithic - the period during which humans evolved - was therefore largely peaceful. Ferguson discusses, among other things, Lawrence Keeley's War Before Civilization (which I reviewed here), Azar Gat's War in Human Civilization (which I read recently and will hopefully review soon), Wrangham & Peterson's Demonic Males and Napoleon Chagnon's influential Science paper "Life Histories, Blood Revenge and Warfare in a Tribal Population".

While I don't agree with Ferguson's conclusion, the interview is highly recommended if you are at all interested in prehistory or human evolution.

The dizzying diversity of human sexual strategies

New Scientist magazine has an interesting article on the huge diversity of human sexual strategies. The article mainly focuses on a construct known as sociosexuality, the tendency to prefer either restricted or unrestricted sex. An excerpt:

Of course, it is not that simple. Women can be as sexually unrestrained as men. In fact, there is a huge overlap in the sociosexuality scores of men and women, with more variation within the sexes than between them. Some researchers are now trying to explain these subtleties in terms of biology and evolution.

Take the fact that women's interest in casual sex can vary wildly over time. A hint that these short-term sexual encounters might have biological and evolutionary advantages comes from the timing of them. Several studies have shown that women are more likely to fancy a fling around the time they are ovulating - although there is no suggestion that this is a conscious decision. Not only that, says David Schmitt of Bradley University, Illinois, women show a shift in preference to men who look more masculine and symmetrical - both indicators of good genes. Women may have a dual strategy going, suggests Schmitt. "Humans infants need a lot of help, so we have pair-bonding where males and females help raise a child, but the woman can obtain good genes - perhaps better genes than from the husband - through short-term mating right before ovulation."

This rather reminds me of David Buss's answer to this year's Edge.org question, "What have you changed your mind about?" (which I blogged about here). Buss said he had realized that female sexual psychology is significantly more complicated than he had previously thought. Just so.

Evolutionary Perspectives on War

New Scientist magazine has a report on a very interesting-looking recent University of Oregon conference entitled "Evolutionary Perspectives on War: An Interdisciplinary Conference" (pdf). I must say, I'm deeply sorry to have missed it - several of the papers presented looks fascinating:

• Steve Frost ("Evidence for coalitional aggression in the hominid fossil record"),
• Steven LeBlanc ("Recent hunter-gatherer warfare as a model for our evolutionary past"),
• Samuel Bowles ("Was Warfare among Ancestral Foragers Sufficiently Common to Affect the Course of Human Evolution?"),
• Joshua Duntley ("Evolutionary psychology of war"), and
• Napoleon Chagnon ("Human conflicts and warfare in history: An evolutionary assessment").
  

Some of the most interesting bits from the New Scientist piece:

Now a new theory is emerging that challenges the prevailing view that warfare is a product of human culture and thus a relatively recent phenomenon. For the first time, anthropologists, archaeologists, primatologists, psychologists and political scientists are approaching a consensus. Not only is war as ancient as humankind, they say, but it has played an integral role in our evolution.

The theory helps explain the evolution of familiar aspects of warlike behaviour such as gang warfare. And even suggests the cooperative skills we've had to develop to be effective warriors have turned into the modern ability to work towards a common goal.

...

If group violence has been around for a long time in human society then we ought to have evolved psychological adaptations to a warlike lifestyle. Several participants presented the strongest evidence yet that males - whose larger and more muscular bodies make them better suited for fighting - have evolved a tendency towards aggression outside the group but cooperation within it. "There is something ineluctably male about coalitional aggression - men bonding with men to engage in aggression against other men," says Rose McDermott, a political scientist at Stanford University in California.

More Infidelity

Talking about infidelity... New Scientist has a report on a recent study in Human Nature that concluded men are better at detecting infidelity than women, but that women are adept at hiding it. A paragraph or two:

"This adds to the evidence that men have evolved defences to detect their partner's infidelity," says David Buss at the University of Texas, Austin. He adds that it demonstrates a "fascinating cognitive bias that leads men to err on the side of caution by overestimating a partner's infidelity".

Andrews suggests that women have countered this by becoming better at covering up affairs. Complex statistical analysis of the data hinted that a further 10 per cent of the women in the study had cheated on top of the 18.5 per cent who admitted to it in the questionnaires, whereas the men had been honest about their philandering.

Infidelity

While society has always accepted that men engage in (or want to engage in) short-term sexual liaisons, women have sometimes been seen as 'pure' and entirely faithful. Evolutionary sexual psychologists, on the contrary, argue (pdf) that men and women pursue mixed sexual strategies, that is, are prone to engage in both long-term and short-term mating. Roughly speaking, the optimal strategy for a woman is to have a long-term relationship with the best mate she can attract but then, subject to an assessment of the risks, to have short-term sexual relationships with higher quality men (pdf). (Since the average woman is more likely to attract the highest quality men into a short-term rather than long-term relationship, she can often increase her fitness by engaging in extrapair copulations. If she can convince her primary partner to care for the children that (sometimes) result, so much the better). The optimal male strategy, on the other hand, is quite a bit more promiscuous: attract the highest quality mate possible to a long-term relationship (at least usually) and then, again taking account of risks, engage in as many extrapair copulations as possible, whatever the quality of the female involved. (As should be clear, I'm ignoring homosexual relationships for present purposes).

All of the above, however, is theory-driven and it leaves open the question of how prevalent infidelity is in the modern world. Determining the true incidence of infidelity is extremely challenging - not least because people find it difficult to admit to it - but we do have some idea. There is fascinating research, for example, showing that a not insubstantial proportion of children - at least 10% - are fathered in extrapair copulations. And a recent review of the literature found that infidelity occurs in about 25% of long-term heterosexual relationships in the United States. The latest is that the New York Times published a pretty good article summarizing some of the recent research and some recent trends, again in the United States. The most titillating finding is that there seems to be a trend towards greater female infidelity, but whether this is due to more honesty on questionnaires or more actual cheating is difficult to determine. What is clear, though, is that sexual fidelity is hardly universal and women are not necessarily less fallible in this regard than men. Obvious, perhaps, but many have denied it...

The latest on ovulation

There is now a pile of research demonstrating that the ovulatory cycle affects female preferences and behavior. Specifically, when ovulating, women find stereotypically masculine males more attractive, place a higher premium on confidence, fantasize about men other than their partners more often and so on. (See Gangestad et. al. [pdf] for a review). And, perhaps most memorably, Geoffrey Miller and colleagues demonstrated that lap dancers' tips are highest (pdf) when they're fertile. (Earning Miller and co an Ig Nobel).

The latest paper (press release here) in this area is by Martie Haselton and Greg Bryant at UCLA on how womens' voices become more high pitched and feminine during ovulation. The abstract:

Recent research has documented a variety of ovulatory cues in humans, and in many nonhuman species, the vocal channel provides cues of reproductive state. We collected two sets of vocal samples from 69 normally ovulating women: one set during the follicular (high-fertility) phase of the cycle and one set during the luteal (low-fertility) phase, with ovulation confirmed by luteinizing hormone tests. In these samples we measured fundamental frequency (pitch), formant dispersion, jitter, shimmer, harmonics-to-noise ratio and speech rate. When speaking a simple introductory sentence, women's pitch increased during high- as compared with low-fertility, and this difference was the greatest for women whose voices were recorded on the two highest fertility days within the fertile window (the 2 days just before ovulation). This pattern did not occur when the same women produced vowels. The high- versus low-fertility difference in pitch was associated with the approach of ovulation and not menstrual onset, thus representing, to our knowledge, the first research to show a specific cyclic fertility cue in the human voice. We interpret this finding as evidence of a fertility-related enhancement of femininity consistent with other research documenting attractiveness-related changes associated with ovulation.

Quote: Richards on the controversy about sociobiology

Janet Radcliffe Richards' Human Nature After Darwin (which I use in a course I teach on the philosophical consequences of Darwinism) is the best, and not unrelatedly, the most level-headed book on the 'Darwin wars' I've ever read. A great quote:

The resistance to sociobiology when it first appeared was fuelled mainly by the conviction of its opponents that any claim about genetically ingrained characteristics must be the first premise of an argument for concentration camps, forced sterilization and the abolition of the welfare state (p. 222).