Best. Experiment. Ever.

Studies have shown that men's testosterone levels increase after sexual stimulation. However, other research shows that merely briefly chatting to a woman also causes testosterone release, making it unclear whether sex, per se, is associated with testosterone changes.

So an intrepid band of researchers decided to find out using a unique methodology. Their paper's called Salivary Testosterone Levels in Men at a U.S. Sex Club and it's about... that.

They first set the scene:

Subjects were recruited from an internationally known "adult social club" in Las Vegas, Nevada, also referred to as a "sex club"... patrons pay a membership fee (akin to an entrance fee) to enter the 18,000 square foot, 2-story club. The first floor is open to all paying customers. The second VIP floor is available for an additional fee and includes a variety of rooms, including fetish rooms...

All are not created equal in this Garden of Eden, however:

Personal observation and communication with staff and members revealed to the investigators that there is a semi-structured hierarchy of patrons in the club. Single men (also referred to as ‘‘sharks’’) are easily identified by an orange wristband. Single women also wear an orange wrist band. Couples are identified by a green colored wristband. Single men are often considered to be a nuisance, as reported by many patrons, and are avoided in certain circumstances. Single women, moderately rare, do not share the stigma.

Anyway, the authors went there and recruited 44 men, of whom 18 ended up having sex, while 26 only looked at other patrons doing so. Saliva samples were taken before and afterwards, and levels of testosterone were measured. The results showed that testosterone increases were much larger in the do-ers than the watchers (see above).

This is an important result, the authors say, because

it runs against the grain of previous human testosterone and sexual stimuli studies in which testosterone increases in response to erotic videos and "courtship"’ behavioral interactions appeared more reliably induced than those related to active sexual behavior... We suggest that the reason for our findings, in contrast to the overarching pattern of previous work, is that lab-based paradigms may quell men’s testosterone responses... engaging in sexual behavior while wired up to machines in a sterile lab may put a damper on men’s arousal and physiological responses.

A good point.

In general, lab studies can be misleading when the behaviors under investigation are the kind of thing you can't really do in a lab. For research on fairly 'basic' memory, perception and cognitive tasks, a lab is probably as good an environment as any but for more complex behaviours it may be systematically misleading. And if a lab is bad, an MRI scanner is even less realistic.

Now, I thought the neuroscientists who threw a cocktail party on their grant money had it good, but these authors really hit a home run by using theirs to get into a sex club. It would be hard to top that but I note that surprisingly little is known about the, er, physiological correlates of lying on a beach in the Bahamas atop a pile of gold bars and bottles of Dom Pérignon. Someone needs to find out and I for one would be willing to undertake this challenge.

 Escasa, M., Casey, J., and Gray, P. (2010). Salivary Testosterone Levels in Men at a U.S. Sex Club Archives of Sexual Behavior, 40 (5), 921-926 DOI: 10.1007/s10508-010-9711-3

Men and Women: From Earth, Not Mars & Venus?

Another day, another debate over how different men and women are, psychologically speaking. Bobbi Carothers and Harry Reis argue that Men and Women Are From Earth.

Their approach is rather interesting.

We sought to empirically determine whether standard gender differences are better conceived as taxonic or dimensional. Although men and women may differ on average in myriad ways, these differences may be dimensional, reflecting different amounts of a given attribute assessed along a single dimension, or qualitative, sorted into fundamentally distinct categories... this difference has considerable importance for understanding the fundamental nature of gender differences.

Using lots of previously published data (13,000 people) and subjecting it to three different methods of statistical "taxometric analysis", they claim that on most psychological measures, there's no evidence that the two sexes are qualitatively different. This is on things like sexual attitudes, personality, and interest in science according to self-report questionnaires.

They give the following hypothetical example to illustrate the idea (my picture based on theirs)

Men are taller than women and also have shorter hair. If you plot a scatterplot of height vs hair length including both genders, you find a negative correlation. However, there is no such correlation within each gender. So gender is a taxon - in this case. There is something qualitatively different between men and women here.

Their argument is that psychological differences between the genders are, in most cases, not because "male" and "female" are two distinct taxons.

So what? I previously covered a paper called The Distance Between Mars and Venus claiming that the difference between men and women on average are larger than previously thought, if you look at all the differences taken together. That's actually consistent with what Carothers and Reis are saying, I think, because it assumes that each of the differences is dimensional and quantitative.

In other words, maybe sexes differ only by a matter of degree, albeit by a larger degree than you'd think at first glance.

All of this leaves open the question of why they differ on average, though. According to yet another study just out, the size of the gap is correlated with the amount of gender inequality in different countries. Women from places where they have much lower incomes, career prospects, etc. compared to men, also endorse more 'feminine' traits.

Personally I consider the question of gender differences largely open because I'm skeptical of self-report questionnaire measures in psychology; objective measures of actual behaviour, stuff like crime statistics, seems to me more interesting.

The fact that the great majority of sex offenders are male, for example, must mean something; I'm not sure what, but I don't think questionnaires will help us find out...

Carothers, B., and Reis, H. (2012). Men and Women Are From Earth: Examining the Latent Structure of Gender. Journal of Personality and Social Psychology DOI: 10.1037/a0030437

Search Trends Reveal Sexual Seasons

Americans are most likely to search for sex online during the early summer and the winter, according to research just published in the Archives of Sexual Behavior.

The authors looked at the Google Trends for a selection of naughty words and phrases, and this revealed a pretty marked 6 month cycle for searches originating from the USA, with two yearly peaks in the search volumes. There was no such pattern for some non-sexual control words.

Here's the graph for pornography searches, with an idealized 6 month cycle also shown for comparison. The data were similar for two other categories of sexual words: prostitution and dating websites. Overall the results seem solid, although in studies like this, I always worry a bit about how the included search terms were chosen; there is a potential for cherry picking (no pun intended).

Those words in full:

The pornography keyword set included 10 keywords used in previous research that individuals tend to use when searching for pornography (‘‘porn,’’ ‘‘boobs,’’ ‘‘xvideos,’’ ‘‘tits,’’‘‘sex,’’ ‘‘pussy,’’ ‘‘hentai,’’ ‘‘xxx,’’ ‘‘nude,’’ and ‘‘milf’’).

In a similar manner, the prostitution keyword set included five keywords that individuals might use to engage in sexual activities that are often illegal (‘‘call girl,’’ ‘‘escort,’’ ‘‘massage parlor,’’ ‘‘brothel,’’ and ‘‘prostitute’’).

Finally, the mate-seeking keyword set included the names of 10 popular websites that individuals often use to find potential mates (‘‘eHarmony,’’ ‘‘Yahoo Personals’’, ‘‘AOL Personals,’’ ‘‘Plenty of Fish,’’ ‘‘Zoosk,’’ ‘‘Singles Net’’ ‘‘Friend Finder,’’ ‘‘JDate,’’ ‘‘Match.com,’’ and ‘‘Okcupid’’).

Heh. I'm not sure I should be quoting those, it might attract some weird traffic to the blog. But oh well.

The authors note that a six-month sexual cycle has been reported before. It crops up in everything from abortion rates, to condom sales, and diagnosis of sexually transmitted infections. But why?

One possibility is that it's purely a social construction driven by the fact that in Western cultures, Christmas and summer are the main holiday seasons; but it could reflect a more primitive biological cycle. Google ought to offer a way to find that out, actually; find a country with a similar climate to the USA, but with different major holidays. China, maybe?

Markey PM, and Markey CN (2012). Seasonal Variation in Internet Keyword Searches: A Proxy Assessment of Sex Mating Behaviors. Archives of sexual behavior PMID: 22810997

The Transsexual Brain

According to a new paper, the brains of male-to-female transexuals are no more "female" than those of men.

The authors write that "The present data do not support the notion that brains of male-to-female transexuals are feminized" and conclude "The present study does not support the dogma that male-to-female transexuals have atypical sex dimorphism in the brain".

That last sentence has gained quite a bit of coverage, including a quote on the Wikipedia page for "transgender".

But is it so simple?

Structural MRI scans were used to compare the size of various brain structures between three groups of volunteers: heterosexual men, heterosexual women and the transexuals (or "MtF"s as I will call them for short) who were diagnosed with gender dysphoria and were "genetically and phenotypically males".

There were 24 in each group, which makes it a decent sized study. None of the MtFs had started hormone treatment yet, so that wasn't a factor, and none of the women were on hormonal contraception.

The scans showed that the non-transsexual male and female brains differed in various ways. Male brains were larger overall but women had increases in the relative volumes of various areas. Male brains were also more asymmetrical.

The key finding was that on average, the MtF brains were not like the female ones. There were some significant differences from the male brains, but they weren't the same differences that distinguished the females from the males.

This is a fairly crude approach. It looks at the groups on average. It's a finding, but there's more you could with this data. It would be better perhaps to look at the male and female groups, and then try to work out which group each individual MtF is most similar to. You could do that using a Support Vector Machine such as was previously used to detect autism.

This would also have the advantage that it would integrate the results across different brain areas: maybe the important thing is not just the size of individual areas but the relative size of one area to another area.

My real problem though is with the language used to discuss the data. The authors say that the study doesn't support "atypical sex dimorphism in the brain" yet this wasn't a study of "the brain". It was a study of one specific aspect of the brain, namely the volume of different regions. There could be all kinds of chemical and microstructural differences that don't show up on these scans.

There are lots of people with severe epilepsy, for example, whose brains clearly differ in some major way from people without epilepsy, yet they look completely normal on MRI. Only using other methods, like EEG, reveals the difference. Because the difference is chemical, not structural.

I have no idea how, or if, the brains of MtF transsexuals are "feminized" but this study doesn't rule it out. Now I'm sure the authors know all this. And in fact they themselves recently published a paper showing atypical neural responses to smelling "oderous steroids" in transsexual people. But while neuroscientists will know what they meant, I worry that studies like this could be miscontrued by other people (like Wikipedia readers) as a result of overenthusiastic language in papers.

Link: Also blogged at BPS Research Digest.

Savic I, & Arver S (2011). Sex dimorphism of the brain in male-to-female transsexuals. Cerebral cortex (New York, N.Y. : 1991), 21 (11), 2525-33 PMID: 21467211

Neuroskeptic Gets "Cited"

...kind of. Last week, I blogged about a Nature paper, Eisenegger et al, reporting that giving women testosterone makes them behave more generously in a money-sharing procedure called the Ultimatum Game.

But just a few days later, PLoS ONE published a paper, Zak et al, finding exactly the opposite result - testosterone decreased generosity in the Ultimatum Game - although that was in men, rather than women. The lead author of the PLoS paper, Paul J. Zak, then "cited" my blog post in an online comment attached to his article, as part of a discussion of the differences between his paper and Eisenegger et al's. This is not a proper citation of course, but it's a start. At least I like to think so.

PLoS have a brilliant policy of having a blog-style comment thread attached to every paper. This is a far better system than the traditional academic policy of allowing comments only in the form of formal "Letters to the Editor" of the journal. This made sense in the days before the internet, but it's long outlived its usefulness.

A Letter has to be approved by the editor of the journal to get published at all. For reasons of space, if nothing else, the number which get printed is small. Even if your Letter does see the light of day, it will be, at minimum, a couple of months after the original paper was published, by which time most readers of the original will have forgotten what the fuss was about. If the original authors reply to your Letter, and you want to reply to their reply, it'll be another couple of months before you can, assuming you still care about it by this point. And so on.

An online comment thread, on the other hand, is "peer review" in its purest form. The key difference is speed - replies take place in real time or close to it, which makes a genuine conversation possible. The fact that anyone on the internet can comment might not seem to be a good thing; the internet makes you stupid, after all. But the standard of comments on PLoS papers is generally very high; I don't know if this is because of a moderation policy, or just because PLoS readers are sensible folk.

A few other journals have adopted a similar commenting system, notably Nature (although apparently not other Nature group journals like Nature Neuroscience), but this is something I'd like to see all journals adopt. Ultimately, I'd like to see the boundaries between the "official" academic literature and "informal" online discussion such as blogs blurred further; PLoS seem to be leading the way in this regard too with their recently announced integration with ResearchBlogging.org although Nature also have a blog section. Exciting times.

Testosterone, Aggression... Confusion

Breaking news from the BBC -

Testosterone link to aggression 'all in the mind'

Work in Nature magazine suggests the mind can win over hormones... Testosterone induces anti-social behaviour in humans, but only because of our own prejudices about its effect rather than its biological activity, suggest the authors.

The researchers, led by Ernst Fehr of the University of Zurich, Switzerland, said the results suggested a case of "mind over matter" with the brain overriding body chemistry.

"Whereas other animals may be predominantly under the influence of biological factors such as hormones, biology seems to exert less control over human behaviour," they said.

Phew, that's a relief - for a minute back there I was worried we didn't have free will. But look a little closer at the study, and it turns out that all is not as it seems. The experiment (Eisenegger et al) involved giving healthy women 0.5 mg testosterone, or placebo, in a randomized double-blind manner, and then getting them to take part in the "Ultimatum Game".

This is a game for two players. One, the Proposer, is given some money, and then has to offer to give a certain proportion of it to the other player, the Receiver. If the Receiver accepts the offer, both players get the agreed-upon amount of money. If they reject it, however, no-one gets anything.

The Proposer is basically faced with the choice of making a "fair" offer, e.g. giving away 50%, or a greedy one, say offering 10% and keeping 90% for themselves. Receivers generally accept fair offers, but most people get annoyed or insulted by unfair ones, and reject them, even though this means they lose money (10% of the money is still more than 0%).

What happened? Testosterone affected behaviour. It had no effect on women playing the role of the Receivers, but the Proposers given testosterone made significantly fairer offers on average, compared to those given placebo. That's not mind over matter, that's matter over mind - give someone a hormone and their behaviour changes.

The direction of the effect is quite interesting - if testosterone increased aggression, as popular belief has it, you might expect it to decrease fair offers. Or, you might not. I suppose it depends on your understanding of "aggression". For their part, Eisenegger et al interpret this finding as suggesting that testosterone doesn't increase aggression per se, but rather increases our motivation to achieve "status", which leads to Proposers making fairer offers, so as to appear nicer. Hmm. Maybe.

But where did the BBC get the whole "all in the mind" thing from? Well, after the testing was over, the authors asked the women whether they thought they had taken testosterone or placebo. The results showed that the women couldn't actually tell which they'd had - they were no more accurate than if they were guessing - but women who believed they'd got testosterone made more unfair offers than women who believed they got placebo. The size of this effect was bigger than the effect of testosterone.

Is that "mind over matter"? Do beliefs about testosterone exert a more powerful effect on behaviour than testosterone itself? Maybe they do, but these data don't tell us anything about that. The women's beliefs weren't manipulated in any way in this trial, so as an experiment it couldn't investigate belief effects. In order to show that belief alters behaviour, you'd need to control beliefs. You could randomly assign some subjects to be told they were taking testosterone, and compare them to others told they were on placebo, say.

This study didn't do anything like that. Beliefs about testosterone were only correlated with behaviour, and unless someone's changed the rules recently, correlation isn't causation. It's like finding that people with brown skin are more likely to be Hindus than people with white skin, and concluding that belief in Brahma alters pigmentation. It could even be that the behaviour drove the belief, because subjects were quizzed about their testosterone status after the Ultimatum Game - maybe women who, for whatever reason, behaved selfishly, decided that this meant they had taken testosterone!

Overall, this study provides quite interesting data about hormonal effects on behaviour, but tells us nothing about the effects of beliefs about hormones. On that issue, the way the media have covered this experiment is rather more informative than the experiment itself.

[BPSDB]

Eisenegger, C., Naef, M., Snozzi, R., Heinrichs, M., & Fehr, E. (2009). Prejudice and truth about the effect of testosterone on human bargaining behaviour Nature DOI: 10.1038/nature08711

Autism, Testosterone and Eugenics

The media's all too often shabby treatment of neuroscience and psychology research doesn't just propagate bad science - it means that the really interesting and important bits go unreported. This is what's just happened with the controversy surrounding a paper from the Autism Research Center (ARC) at Cambridge University - Bonnie Aeyeung et. al.'s Fetal Testosterone and Autistic Traits. For research published in a journal with an impact factor of 1.538 (i.e. not good), it's certainly attracted plenty of attention - but for all the wrong reasons.


The Autism Research Center is headed by the dashing Simon Baron-Cohen, also one of the authors on the paper. He's probably the world's best-known autism researcher, and the author of some excellent books on the subject including the classic Mindblindness and The Essential Difference. Mindblindness, in particular, probably deserves a lot of the credit for interesting a generation of psychologists in autism. A big cheese, in other words. Surely his greatest achievement, however, is being Borat's cousin.

Baron-Cohen is famous for his theory that the characteristic features of autism are exaggerated versions of the allegedly characteristic features of male, as opposed to female, cognition. Namely, autistic people have difficulties understanding the emotions and behaviour of other people ("empathizing"), but may show excellent rote memory and understanding of abstract, mathematical or mechanical systems ("systematizing"). He and his colleagues have also hypothesised that an excess of the well-known masculinizing hormone testosterone, could be responsible for the hyper-male brains of autistics, just as testosterone is responsible for the development of masculine traits in boys. Amongst other things this would explain why rates of diagnosed autistic spectrum disorders are several times higher in boys than in girls.

Now, this is one of those wide-ranging theories which serves to drive research, rather than strictly following from the evidence. It's a bold idea, but there is, at the moment, not enough data to confirm or reject this idea. The simple view that testosterone = maleness = autism is almost certainly wrong, but it's a neat theory, there's clearly something to it, and, as one of the commentators on the paper puts it

To date, no theory of autism has provided such a connecting thread linking etiology, neuropsychology and neural bases of autism.

Anyway, the paper reports on an association between testosterone levels in the womb and later "autistic traits" in childhood. 235 healthy children were studied; for all of these kids, the levels of testosterone in the womb during pregnancy were known, because their mothers had had amniocentesis, collecting a sample of fluid from the womb. Amniocentesis is not risk-free and it can't be done for research purposes, but the mothers here got amniocentesis for medical reasons and then agreed to take part in research as well. Testosterone levels in the amniotic fluid were measured; notably, this probably represents testosterone produced by the fetus itself, rather than the mother.

The headline finding was that fetal testosterone (fT) levels were correlated with later "autistic traits", as judged by the mothers, who filled out questionaires about their kid's behaviour at the age of about 8. Here's a nice plot showing the correlation. The vertical axis, "AQ-child total", is the parent's total reported score on the "Autism Quotient" questionaire. Higher scores are meant to indicate autism-like traits (although see below). You'll also notice that fT levels are much higher in the boy fetuses than in the girl fetuses - not surprisingly. That's it - a statistically significant association, but there is still a lot of scatter on the plot. The correlation was still significant if the very high-scoring children were ignored. A similar pattern emerged using a different autism rating scale, but was less significant - probably because many scores were very low.
So, this was a perfectly decent study with an interesting result, but it's only a correlation, and not an especially strong one. How did this get written up? New research brings autism screening closer to reality puffed the Guardian's front page! They suggested that measuring fetal testosterone levels might be a way of testing for autism pre-natally, thus sparking off an entirely formulaic debate about the ethics of selective abortion, the usual denunciations of "eugenics", etc. Long story short - Catholics are against it, the National Autistic Society say it's a dilemma, while a family doctor on Comment is Free is unsure about the "test" because she can't read the article: she doesn't have access to the journal.

Lest it be said that the ethical debate is important in itself, even if the details of the testosterone-based screening test might be inaccurate, bear in mind that "testing for autism" is likely to raise unique issues. Are we talking about a test which could distinguish "low-functioning autism" - which can leave children unable to lead anything like a normal life - from "high-functioning autism", sometimes associated with incredible intellectual achievement? Would the test distinguish classical high-functioning autism from Asperger's? When and if a test is developed, these will be crucial questions. You cannot simply speculate about "a test for autism" in the abstract.

Anyway, after a few days of this nonsense Baron-Cohen rightly protested that the paper had nothing to do with prenatal testing, and that such testing isn't on the horizon yet.

The new research was not about autism screening; the new research has not discovered that a high level of testosterone in prenatal tests is an indicator of autism; autism spectrum disorder has not been linked to high levels of testosterone in the womb; and tests (of autism) in the womb do not allow termination of pregnancies.

Most importantly, there were no autistic kids in the study - all of the children were "normal", although some were rated highly on the autism measures. Moreover, as the plot above shows, any testosterone-based screening test would be very inaccurate. Which is why no experts proposed one.

Just like last time. Back in 2007 the Observer (the Sunday version of the Guardian) ran a front-page article about Simon Baron-Cohen's work on the epidemiology of autism. They said that he'd found that autism rates in Britain were "surging"; they probably aren't, and Baron-Cohen's data didn't show that they were, but despite this the Observer took weeks to clarify the issue (for details of the saga, see Bad Science.) In both cases, some important research about autism from Cambridge ended up on the front page of the newspaper, but the debate which followed completely missed the real point. It would have been better for all concerned if the research had never caught the attention of journalists at all.

The actual study in this case is very interesting, as are the three academic commentaries and a response from the authors published alongside it. I can't cover all of the nuances of the debate, but some of the points of interest include: the question of whether the Autism Quotient (AQ) questionaire actually measures autistic behaviours, or just male behaviours; the point that it may be testosterone present in baby boys shortly after birth, not in the womb, which is most important; and the interesting case of children suffering from Congenital Adrenal Hyperplasia, a genetic disorder leading to excessive testosterone levels; Baron-Cohen et. al. suggest that girls with this disorder show some autism-like traits, but this is controversial. Clearly, this is a crucial point.

Overall, while it's too soon to pass judgement on the extreme male brain theory or the testosterone hypothesis, both must be taken seriously. As for autism prenatal testing, I suspect that this will only come when more of the genetic causes of autism are identified. There is no single "gene for autism"; currently a couple of genes responsible for a small % of autism cases are known: CNTNAP2, for example.

Once we have a good understanding of the many genes which can lead to the many different forms of autistic-spectrum disorders, genetic testing for autism will be possible; I doubt that testosterone levels or anything else will serve as a non-genetic marker, because autism almost certainly has many different causes, and many different associated biochemical abnormalities. Maybe I'm wrong, but even so, if you're worried about hypothetical people aborting hypothetical autistic fetuses, you don't have to worry quite yet. Actual children are dying in Zimbabwe - worry about them.

[BPSDB]

Bonnie Auyeung, Simon Baron-Cohen, Emma Ashwin, Rebecca Knickmeyer, Kevin Taylor, Gerald Hackett (2009). Fetal testosterone and autistic traits British Journal of Psychology, 100 (1), 1-22 DOI: 10.1348/000712608X311731