Did Boys Use To Wear Pink?

There's a belief that the colours we associate with the genders - pink for girls and blue for boys - used to be the other way around.

About 100 years ago, we're told, boys wore pink clothes, but then during the early 20th century, it flipped over. This is often used as an example of how arbitrary gender stereotypes are.

However according to psychologist Marco Del Giudice, the whole "pink-blue reversal" is an 'urban legend'. He argues that there's really only anecdotal evidence for the existence of the previous blue-girls pink-boys association.

The exceptions are four magazine articles - quoted in the paper that started the whole debate - which seem to provide documentary evidence. These associate girls with blue, but Giudice says that two of these might have been accidental typos, that swapped 'pink' with 'blue', while the other two may have represented a sneaky campaign by early feminists to subvert the blue-pink patriarchy.

Hmm. I don't really buy that. However Giudice has a stronger argument, which is that according to Google NGram, a searchable database of over 5 million books, there are lots of instances of the terms "blue for boys" and "pink for girls" going back to 1890, but none for the reverse at any time point:

Fair enough. However it's a big step from that to the idea that

the pink-blue convention may ultimately depend on innate perceptual biases toward different regions of the color spectrum in the two sexes (Hurlbert & Ling, 2007)

Del Giudice, M. (2012). The Twentieth Century Reversal of Pink-Blue Gender Coding: A Scientific Urban Legend? Archives of Sexual Behavior, 41 (6), 1321-1323 DOI: 10.1007/s10508-012-0002-z

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

Should You Judge A Book (Woman) By The Cover?

"Do physically attractive women possess particularly attractive inner attributes?"

So ask the authors of a study just out in Psychological Science: Don't Judge a Book by Its Cover, Revisited. Their answer? People do tend to judge (female) books by their covers, but we shouldn't.

Psychologists Segal-Caspi and colleagues took 118 female Israeli students and videotaped them walking into a room and reading a weather forecast. Then other students - male and female - judged the 'targets' on attractiveness, but also tried to work out their personality, purely based on 60 seconds of video.

So what happened?

The judges judged prettier women as having stereotypically 'better' personality traits e.g. less neurotic and more friendly. Interestingly, both male and female judges did this, and there were no significant differences between the genders.

So there's a tendency to think that those we find attractive are also beautiful on the inside - but, that's all an illusion, say the authors. The targets were also rated themselves on personality, and these self ratings told a different story - there was no correlation between personality and average ratings of attractiveness.

There were however some small differences in self-reported values, with attractiveness being associated with valuing tradition and conformity, but not 'self-direction'.

So there we have it. Books, covers, don't judge 'em by 'em. It would have been better if this study had included both male and female 'targets', though, and the whole thing does rely on the validity of self-report, though no more than any other psychology paper.

The journal Psychological Science has been criticized recently, accused of publishing findings that probably aren't true and wouldn't be interesting even if they were. I don't think that applies to this, though.

On the contrary, this is the kind of study that psychologists should do more of.

The subject may seem crude, unsophisticated and not very 'scientific' but like it or not, it's one that people care about. Many people have strong views on issues like this (one way or the other), ones based essentially on hearsay, and personal recollections, i.e. on not much to speak of.

By addressing issues such as these, psychologists could really help to clear up some messy debates and damaging misconceptions.

Segal-Caspi, L., Roccas, S., and Sagiv, L. (2012). Don't Judge a Book by Its Cover, Revisited: Perceived and Reported Traits and Values of Attractive Women Psychological Science, 23 (10), 1112-1116 DOI: 10.1177/0956797612446349

We're Probably Not Getting Dumber

There's been buzz over the past few days in the idea that humans have been getting stupider for the past few millennia. That's according to Stanford's Gerald R. Crabtree -

I would wager that if an average citizen from Athens of 1000 BC were to appear suddenly among us, he or she would be among the brightest and most intellectually alive of our colleagues and companions, with a good memory, a broad range of ideas, and a clear-sighted view of important issues. Furthermore, I would guess that he or she would be among the most emotionally stable of our friends and colleagues.

OK. How so?

Crabtree's argument in a nutshell:

In Part I, he outlines the latest evidence showing that many thousands of genes contribute to human cognitive ability, and that because mutation rates are high (higher than previously believed), any given individual probably carries harmful variants of many of these genes. This is quite possibly true ,and interesting, but by itself it's nothing to do with declining IQ.

In Part II, Crabtree says that during human evolution, all of these genes were under strong selection pressure because any human or proto-human who wasn't smart enough to hunt, fight and survive in the stone age environment, would get eaten by a predator or starve. However, after these hunter-gatherer tribes became settled farming communities (in say 6000 BC), they were no longer so vulnerable, so the less intellectually able could live... and breed... leading to ever-more unintelligence genes.

Now, there's a lot of problems here. Many have said that this is all a bit like eugenics, and indeed it is, but that doesn't necessary mean it's wrong... no, it's wrong because the argument is flawed.

For instance, it's already been pointed out that, even if it recently got easier to stay alive, that doesn't mean it's got easier to get laid lots and have lots of kids; and sexual selection is a powerful force in evolution, perhaps even stronger than survival, and it probably favours higher intelligence.

However, there are other issues.

The idea that hunter-gatherers have especially hard lives is dubious. There's good evidence that life expectancy and health fell when hunter-gatherer societies settled down and got agriculture. Today, survival doesn't exert much of a selective pressure in most parts of the world but life stayed pretty precarious (by modern standards) until at least the 19th century.  You could indeed argue that 8,000-odd years of agriculture made us smarter than ever before, and that we're enjoying the benefits . In which case we'd be smarter than someone from 1000 BC, who only had 5,000 years or so.

Crabtree does acknowledge that agriculture changed selection pressures. He suggests that it would have made it more important to be immune to the various diseases that emerged when our population density rose. But this isn't enough - for his argument to work, intelligence would also have needed to become less important with agriculture, and whether that's true is really not clear at all. Maybe it did. Maybe it didn't. There's a prejudice in modern culture against 'ignorant peasants' and 'dumb hicks', but farming is not easy.

Even if we do grant that cognitive evolutionary pressures have eased since 1000 BC, it's not clear that this would make us 'less intelligent'. 'Intelligence' is not one thing. To simplify, it might be that there's a trade-off between 'book smarts' and 'street smarts', and that you used to need the latter to survive. A society in which everyone survives would then allow more people the luxury of being book-smart. Would Einstein or Newton would have made good peasants?

Crabtree's arguments are interesting, but they're entirely speculative. There's just no hard evidence for the decline of intelligence over recent millennia. Since we can't go back in time and do IQ tests, there never will be, although he does suggest an experiment, using genetics, that might be able to check whether there's been a build-up of harmful mutations.

But until then, as he puts it,

in the meantime I’m going to have another beer and watch my favorite rerun of ‘Miami CSI’ (if I can figure out how to work the remote control).

Crabtree, G. (2012). Our fragile intellect. Part II Trends in Genetics DOI: 10.1016/j.tig.2012.10.003 

Crabtree, G. (2012). Our fragile intellect. Part I Trends in Genetics DOI: 10.1016/j.tig.2012.10.002

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

Facial Expressions of Emotion Still Culturally Universal

Do people from different cultures express emotions differently?

A new paper says yes: Facial expressions of emotion are not culturally universal. But as far as I can see the data show that at least some of them very much are universal.

First some background. The authors, Rachael Jack and colleagues of Glasgow, have published before on this theme. Back in 2009 I blogged about one of their previous papers, which showed that East Asians were less accurate than Westerners at categorizing certain emotions.

But although there were cultural differences in ability to classify some emotions, East Asians still did much better than just guessing. To me, this said that there are fundamental universal emotional expressions, albeit culture can subtly modify them.

That's my verdict on this study as well.

The authors adopted a new (and very clever) method this time. Rather than just showing people photos of actors posing expressions, and asking subjects to label them with an emotion, they generated virtual faces using a 3D modelling software, and made the faces display "expressions", with their 41 virtual facial muscle groups.

Subjects (either white Westerners, or recent East Asian immigrants) saw 4,800 random assortments and had to label each one; the authors could therefore work back to calculate their "mental model" of that emotion based on the set of facial movements that best fit, individually (it reminds me of this method).

What happened? The Westerners mental models clustered into the classic 6 "basic emotions" of happy, sad, disgust, fear, anger, and surprise. The Asians however didn't; although they were pretty much the same on happy and sad, they were less clear about the other 4.

But how much less? Take a look:

Cluster analysis and dissimilarity matrices of the Caucasian and Asian models of facial expressions. In each panel, vertical color coded bars show the k means (k = 6) cluster membership of each model. Each 41-dimensional model (n = 180 per culture) corresponds to the emotion category labelled above (30 models per emotion). The underlying grayscale dissimilarity matrices represent the Euclidean distances between each pair of models, used as inputs to k-means clustering. Note that, in the Caucasian group, the lighter squares along the diagonal indicate higher model similarity within each of the six emotion categories compared with the East Asian models. Correspondingly, k-means cluster analysis shows that the Western Caucasian models form six emotionally homogenous clusters... In contrast, the Asian models show considerable model dissimilarity within each emotion category and overlap between categories.

This shows that yes, Asians "confused" some emotions more than Westerners but the basic emotional distinctions seemed to be intact, with Happy and Sad especially solid.

And look at these examples of the "mental model" for one subject of each group: yes they're different, but not very.

These are fine results, and I think there are real questions over whether the Ekman 6 emotions model really captures the essence of human emotions (especially negative ones.)

But, especially in the context of previous work from the same authors, I don't think these data really justify the paper's title ("Facial expressions of emotion are not culturally universal"), or the statement that

Our data directly show that across cultures, emotions are expressed using culture-specific facial signals. Although some basic facial expressions such as fear and disgust originally served as an adaptive function... facial expression signals have since evolved and diversified to serve the primary role of emotion communication during social interaction. As a result, these once biologically hardwired and universal signals have been molded by the diverse social ideologies and practices of the cultural groups who use them for social communication.

Overall, (ahem) I'm happy to admit that these data show some surprising cultural differences, but I'm afraid that the authors' overblown rhetoric makes me disgusted, sad and angry.

Jack, R., Garrod, O., Yu, H., Caldara, R., & Schyns, P. (2012). Facial expressions of emotion are not culturally universal Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1200155109

Homosexuals Are Smart?

Evolutionary psychologist Satoshi Kanazawa has never been far from controversy. When he's not having his blog cancelled for saying black women are unattractive, he's arguing that some nations just aren't smart enough to be monogamous.

Given which, his latest work, saying that gay people are smarter on average, is probably his most politically correct paper in years, strange as that may sound.

In three large population surveys (USA's AddHealth and GSS, UK's NCDS), Kanazawa found a small positive correlation between estimated IQ and self-reported homosexual behaviour or identity.

Now I'm not sure what to make of this. He controlled for confounds such as race, religion and political orientation (and those correlations are interesting in themselves), but you can never measure and correct for everything in a study like this.

Kanazawa interprets all this in terms of the Savanna hypothesis, essentially the idea that intelligence allows us to transcend our evolutionary programming (according to which we ought to all be straight, amongst many other things) -

The Savanna-IQ Interaction Hypothesis (Kanazawa, 2010a), implies that the human brain’s difficulty with evolutionarily novel stimuli may interact with general intelligence, such that more intelligent individuals have less difficulty with [evolutionarily novel] stimuli than less intelligent individuals...

Evolutionarily novel entities that more intelligent individuals are better able to comprehend and deal with may include ideas and lifestyles that form the basis of their preferences and values; it would be difficult for individuals to prefer or value something that they cannot truly comprehend...

However, it could be that in America and the UK today, smarter people tend to end up in the kind of social circles where being gay is (for whatever reason) more acceptable.

My main problem with this is that the effects are very small. For example, in the AddHealth study, IQ in childhood was correlated with later adult sexual identity with a coefficent of 0.013... but the association of homosexuality with political attitude (liberalism) of 0.613, 60 times as high. (Edit: But these are unstandardized regression coefficients, so they cannot be directly compared. The coefficients represent the change in homosexuality per 'point' change in the other variable, but IQ varies more than political orientation, because political attitudes were measured on a 5 point scale in AddHealth but IQ has a mean of 100 points. Multiplying by the SD of the variables in question, which is one way to correct for this, gives a coefficient for IQ of 0.202 and for political attitude is 0.468, so intelligence is not as far behind politics as as I thought. Thanks to a reader for pointing that out and apologies for the error.)

The Savanna hypothesis is all very well, but does it predict such small effects? Isn't there a point where very weak evidence in favor of a theory actually becomes evidence against it...?

Kanazawa, S. (2012). Intelligence and Homosexuality Journal of Biosocial Science, 1-29 DOI: 10.1017/S0021932011000769

Broken Hearts and Broken Livers

In a new paper, Beyond the Blues, German psychologists Postert et al discuss how the Hmong people of South East Asia talk about sadness - or rather, how they don't, because they don't really have a word for it.

Based on anthropological fieldwork in a number of Hmong communities in Laos, the focus of this article is on the Hmong term tu siab, literally "broken liver". This is usually translated as "sadness" in the dictionaries, but the authors say that, although it is certainly the closest thing the Hmong have to a word meaning sadness, it is not the same because:

The instance of becoming ‘sad’ in Western contexts is that ‘something bad happened’... This may involve disappointment in personal relationships, but also other afflictions beyond the social realm. At the core of the emotional experience of ‘sadness’ are basic violations of values deeply embedded in Western conceptions of the individual. The afflicted individual feels resigned, passive, out of control...

In Hmong language, the concept of ‘broken liver’ has a strong emphasis on kin relations. It pertains very often to social situations of isolation and neglect from one’s kin including consanguines, patrilineal ancestors, or affines or their unmarried daughters in cases of romantic love. Persons with a ‘broken liver’ may have been voluntarily offended, excluded, or separated from these persons by bad fortune...

One of the highest Hmong values, a person’s vital social integration, is at stake here. However, a state of ‘broken liver’ is usually far from resignation. Contrary to the assumed passivity of a ‘sad’ individual, a ‘broken liver’ is an affective marker highly mobilising social relations and interdependencies ... having a member in one’s group whose liver is ‘broken’ appeals to the collective commitment of all relatives...

[like the English "guilt" and "shame", but unlike "sadness"] ‘broken liver’ demonstrates characteristics of a socio-moral emotion in everyday pragmatics of Laotian Hmong villages. It is typically evoked in a – conscious or unconscious – transgression of an important sociocultural rule. When a man is assumed not to accord to basic principles of social reciprocity by keeping substantial gains from an opium sale for himself, close relatives may develop signs of a ‘broken liver’ signalling their disapproval...

In short, the argument is that the Hmong "broken liver" differs from our "sadness" in being an active response rather than a passive reaction, a social statement rather than an individual feeling, in having a moral dimension, and so on.

But isn't that much like our "broken heart"?

"Breaking someone's heart" is a moral issue. It's not good to be a heartbreaker. If someone broke your friend's heart, you'd be angry. It's a specifically social emotion in the sense that it generally results from betrayal, abandonment, or disrepect. It's true that while the Hmong's "liverbreak" seems to extend to all close relationships, "heartbreak" often has a romantic connotation; but we do talk about "breaking your mother's or father's heart", so even that's not an absolute rule.

Consider this recently broken heart. Doesn't Tulisa's heartbreak fit the tu siab bill?

If so, then the main difference between Hmong and English terminology is that they only have a concept of 'heartbreak', and lack a general concept of 'sadness'. That's quite interesting, but I'm not sure how much to read into it. English doesn't have a word for 'déjà vu'; we had to borrow it from the French, but surely that doesn't mean that no English people ever felt it until the French explained it to them.

I'm no expert but judging by this paper, Hmong emotion terminology is really very similar to ours. The big difference is that the Hmong (in common with other East Asian cultures) link emotions to the liver, which to Westerners sounds silly, but it's no more silly than our talk about emotions being in the heart. They're both just metaphors.

Replace "liver" with "heart", and the following Hmong terms (listed in the paper) look very familar -

• zoo siab  ‘pleased, happy’ (lit. ‘good liver’)
• siab npau  ‘angry’ (lit. ‘liver boiling’)
• chob siab  ‘inwardly offended’ (lit. ‘pierced liver’) etc.

Don't those all make sense? We talk about being "hearty" or "heartened", "taking heart" or having our "hearts lifted" when we're happy or confident; our "blood boils" when we're angry; we talk about feeling "cut", "stung", "pierced" by criticism or insults, and we suffer "heart-rending" traumas.

This is certainly a very interesting paper, but it didn't leave me feeling that the Hmong's emotional life is all that different to ours.

Postert, C., Dannlowski, U., Müller, J., and Konrad, C. (2012). Beyond the Blues: Towards a Cross-Cultural Phenomenology of Depressed Mood Psychopathology, 45 (3), 185-192 DOI: 10.1159/000330944

The Case of the Phantom Phantom Finger

A "phantom limb" is the sensation that an amputated limb (or other body part) is still present.

They can be distressing, especially when they're accompanied by pain in the "limb" which is not uncommon. The leading theory of why they happen is that the brain areas that used to receive sensations from the lost appendage respond to input "spilling over" from nearby brain regions.

Anyway, a phantom limb is bad enough, but a paper just out reports on the case of a phantom finger that was never there in the first place.

A woman, RN, was born with an abnormally short right arm; her right hand was also malformed, with a shortened thumb, no index finger, and immobile ring and middle fingers. Only the little finger was present and correct.

At the age of 18, she then had the misfortune to suffer a car crash; the injuries meant that her right hand had to be amputated. She soon found herself experiencing a phantom hand - with all five fingers. Three of them felt like they were normal length; the "thumb" and "index finger" felt shorter than normal, but remember that the original hand had no index finger at all.

RN also suffered from phantom pains and was distressed by the fact that the "hand" felt like it was bent into an impossible posture. Fortunately, the mirror box technique was able to set things right; while the phantom was still there, it was no longer painful, and all the fingers were the right length.

This is a remarkable case. The authors of the paper, Paul McGeoch and V. S. Ramachandran (perhaps the best known phantom-limb expert) say that it could mean that we're born with an innate, hard-wired "body plan" in the brain, regardless of the way our body actually develops -

While RN’s phocomelic [abnormal] hand was present she did not experience any phantom sensations. Thus, although severely deformed, the mere presence of the hand was sufficient to inhibit the innate representation of her normal hand and prevent any phantom sensations from emerging, presumably from tactile, proprioceptive and visual feedback... the amputation of her hand appears to have disinhibited these suppressed finger representations in her sensory cortex and allowed the emergence of phantom fingers that had never existed in her actual hand.

They do consider alternative explanations though -

Clearly it is beholden on us to consider whether RN’s descriptions do not describe a genuine sensory experience, but rather are confabulatory in origin. We do not believe this to be the case, since if she were confabulating then it would seem unlikely that she should report that her phantom hand had five fingers, but that they were not all of normal length; if this were simply ‘wishful thinking’ then she would likely claim to have five normal length fingers. This appears a persuasive, although not definitive argument, against confabulation.

Seems like a fair assessment.

I don't even know what you'd call the phantom "index finger". A pseudo-phantom? A phantom phantom?

McGeoch, P., and Ramachandran, V. (2012). The appearance of new phantom fingers post-amputation in a phocomelus Neurocase, 18 (2), 95-97 DOI: 10.1080/13554794.2011.556128

A Correction

In my previous post, on the paper A Facial Attractiveness Account of Gender Asymmetries in Interracial Marriage by Michael B. Lewis, I wrongly stated that it was unclear from the paper whether the research assistant who selected the Facebook images was blind to the hypothesis of the study.

In fact, the paper did state that they were "a naive research assistant", something I missed. Apologies for this avoidable mistake. I've corrected the post.

I'd also like to take this opportunity to remind everyone that sometimes comments will get caught in the Blogger spam filter, especially if they're long or contain links, but it can happen to any comment. If your comment doesn't appear immediately, don't worry, I will manually approve such comments as soon as possible.
 
Lewis, M. (2012). A Facial Attractiveness Account of Gender Asymmetries in Interracial Marriage PLoS ONE, 7 (2) DOI: 10.1371/journal.pone.0031703

The Evolutionary Psychology of Race, Beauty and Marriage

There are some papers that you can tell are going to be hot potatoes just from the titles. This is one of them: A Facial Attractiveness Account of Gender Asymmetries in Interracial Marriage.

Coming so soon after The Unconquered World, you'd be forgiven for thinking I am taking this blog in a more linkbaiting direction because I'm planning to introduce ads. I'm really not, it's just a coincidence.

The paper claims that white women are on average more attractive than black, while East Asians are prettier still.  For men, however, the positions were reversed (and the effects were even stronger.)

Saying that black women are on average less attractive than others was what got evolutionary psychologist and blogger Satoshi Kanazawa into spot of bother last year. The current paper agrees with Kanazawa on that point (though doesn't cite him)... although it also declares Kanazawa to be part of the least attractive race for males, so I don't know how happy he'll be about it.

Author Michael B. Lewis of Cardiff University took 600 Facebook photos "from people who were members of groups associated with further and higher education bodies either in the UK (for White faces), sub-Saharan Africa (for Black faces) and East Asia (for Asian faces)."

Photos with a "weird expression" and people who "looked" under 18 or over 30 were excluded. The actual ages were not checked. Hmm.

A panel of 40 British students (half male) were asked to rate all of the opposite-sex faces for attractiveness from 1 to 10. The ethnicity of the rater made no difference to the results but there were only 5 black and 6 Asian students out of 40 though:

After this we get some models proposing how these data might relate to British and American inter-racial marriage patterns, and some evolutionary speculation regarding why this might have evolved - Asia was cold so men were in short supply, that kind of thing - but that's all assuming the basic data are solid.

There are many possible objections to the methodology here, some of which are addressed in the paper, but there's one massive that isn't -

It's not stated how the Facebook images were gathered. All we're told is that "a research assistant" got the images from higher education institutions. Were they, consciously or subconsciously, picking photos that fitted the expected some pattern?

We're not told whether or not this individual was aware of the hypothesis of the study when they chose the pics. If they were aware, it's a fatal confound; (Edit - 19th Feb 2012 - The paper in fact says that the research assistant was "naive" i.e. that they were not aware of the hypothesis of the study, which is of course sound methodology. I missed this statement in the first version of this post.)

However, the broader point remains that they might have been selecting in line with their own preferences, or some other bias. Clearly, there's much room for cherry picking the examples, based on whether they "looked" too young or old, or had a "weird" expression...

Link: Also blogged about here.

Lewis, M. (2012). A Facial Attractiveness Account of Gender Asymmetries in Interracial Marriage PLoS ONE, 7 (2) DOI: 10.1371/journal.pone.0031703

Tired Brains Are More Excitable

An important new study shows how being awake causes progressive changes to the brain. This could shed light on the function of sleep - but it also raises warnings for neuroscientists.

Italian researchers Huber et al report that Human Cortical Excitability Increases with Time Awake. The experiment was conceptually simple - they measured cortical excitability when people were well rested and then looked to see how it changed as they were kept awake for over 24 hours.

The participants woke up at 7 am on Day 1 and were kept awake all of that day, all of the subsequent night, and all of Day 2. The excitability measurements spanned a period of 30 hours, from 9 am to 3 pm the next day. They were finally allowed to go to sleep on the next night and one final session took place on Day 3. I hope they got well paid for taking part.

The results showed a nice linear increase in excitability with increasing time spent awake. Sleep put this back to normal - mostly:

"Excitability" was measured using electroencephalography (EEG) combined with transcranial magnetic stimulation (TMS). Essentially, they zapped the brain (left frontal cortex) with a strong magnetic pulse, and measured the electrical activity that this provoked in the brain.

It was a small study but the findings look solid, with all six participants showing clearly higher stimulation-evoked potentials after sleep deprivation. EEG cortical theta band activity was also correlated with time spent awake, replicating previous findings.

The authors say that these data fit with the idea that the function of sleep is to prevent the brain from becoming too excitable. I previously described this as the "defragmentation" hypothesis of sleep.

The theory goes that while we're awake, our brains are constantly forming new and stronger synaptic connections, as we learn and remember. Most of the new connections are excitatory. However this creates a problem because the brain must maintain a delicate balance between excitation and inhibition. Too much neural excitation and you'll have a seizure, amongst other things. So some researchers believe that during sleep, the brain "prunes" the new excitatory connections in such a way that the information they store is preserved, but the overall excitability is reset.

These data are the first clear-cut human evidence in favor of the theory. Most of the previous work was in animals.

So sleep researchers will be very interested by this paper, but all neuroscientists should take note. If being awake changes cortical excitability, it means that the time of day that you conduct your experiments could have an impact on your results. EEG researchers should pay particular notice, but it could well be that these changes also affect the fMRI signal.

This could be a serious confounding factor in your data. Suppose, for example, that your healthy controls are more likely to have jobs than your patients with, say, autism or depression - which is sadly all too common. Now people with jobs would naturally prefer to attend your study later in the day, after work, leaving those with more flexible schedules to come in bright and early... you see the problem.

Huber, R., Maki, H., Rosanova, M., Casarotto, S., Canali, P., Casali, A., Tononi, G., and Massimini, M. (2012). Human Cortical Excitability Increases with Time Awake Cerebral Cortex DOI: 10.1093/cercor/bhs014

Men and Women - Alien Personalities?

How different are men and women? Are they from two different planets?

In the cleverly-titled The Distance Between Mars and Venus, the authors argue that personality-wise, the differences between men and women have been underestimated by previous studies because they used simplistic statistics.

Traditional studies of gender and personality have given some men and some women a personality quiz, and calculated the average male and female scores on the different aspects of personality.

When you do this you find that there are differences, but that the standardized effect sizes are fairly small, which means that there is a lot of overlap. Even on measures where men score above women on average, lots of men score below the female average, and vice versa, like this:

Traditional studies of overall gender differences have looked to see the differences between the average man and woman on each personality aspect, and then averaged the differences on each scale to get an "overall difference" score. Which comes out as fairly small.

The authors of the new paper say that this approach fails to capture the true difference and they give a helpful analogy of why:

Consider two fictional towns, Lowtown and Hightown. The distance between the two towns can be measured on three (orthogonal) dimensions: longitude, latitude, and altitude. Hightown is 3,000 feet higher than Lowtown, and they are located 3 miles apart in the north-south direction and 3 miles apart east-west.

What is the overall distance between Hightown and Lowtown? The average of the three measures is 2.2 miles, but it is easy to see that this is the wrong answer. The actual distance is the Euclidean distance, i.e. 4.3 miles – almost twice the "average" value.

The main novel argument of this paper is that if you calculate the distance (technically the Mahalanobis distance) in 'personality space' between men and women then you get a larger value than if you just average the differences on each measure.

The paper also uses a couple of other methods that increase the effect sizes, namely using 15 different personality measures instead of the more common Big 5, and adjusting the differences upwards to take account of the fact that quizzes only imperfectly measure underlying 'latent' personality traits.

I don't want to get into the debate over how valid the underlying data are (a 1993 sample of over 10,000 American adults, used to standardize the 16PF questionnaire). There are lots of technical comments here. I'm going to focus on the distance method.

It's a very interesting approach and certainly raises questions about merits of the old approach, which when you think about it, does seem a bit crude. But I'm not sure that the average person is talking about distance in a hypothetical space when they talk about "personality differences".

As an analogy, consider the dog breeds Labrador and Golden Retriever. These are regarded as being pretty similar kinds of dog. On any given feature, the average differences are small, at least compared to the diversity of other breeds. They're roughly the same size, much the same build, coat type etc.

They are distinct breeds. This surely means that when you take all of the differences together, they define distinct regions of "dog space" (which has dozens or hundreds of dimensions), with little or no overlap.

Yet they are still regarded as similar. "Similar" and "distinct" are not mutually exclusive. In fact, isn't the definition of 'distinct yet similar' that two things separate in some kind of feature-space, but don't differ much on any one measure?

So I would say that these data show that, while men and women may be distinguishable in personality, they could still be similar. This is something of a semantic point but not "merely" semantic: it changes the interpretation of the numbers.

J. S. Hyde, who is most associated with the view that gender differences are small, makes a similar (or do I mean distinct?) point in her comment on the paper:

The gender difference found is along a dimension in multivariate space that is a linear combination of the original variables transformed into latent variables...[but] the resulting dimension here is uninterpretible. What does it mean to say that there are large gender differences on this undefined dimension in 15-dimensional space created from latent variables? The authors call it global personality, but what does that mean?

Her questioning of what the direction along which men and women differ means, is (I think) the same question I'm asking about whether it disproves the idea of "similarity", in the ordinary sense of the term.

Finally, take a step back and the whole debate seems a bit circular because, by definition, "personality" means "things that differ between individual people". Things we are have in common aren't even in the picture. Two groups could differ in personality space but still be very close in the much larger space of "possible creatures". There's no personality trait for 'being human'.

Del Giudice, M., Booth, T., and Irwing, P. (2012). The Distance Between Mars and Venus: Measuring Global Sex Differences in Personality PLoS ONE, 7 (1) DOI: 10.1371/journal.pone.0029265

What're You Lookin' At (When You Dream)?

Why do our eyes move during sleep?

Here at Neuroskeptic we've already asked why do we sleep? and why do we dream? There are plenty of theories, but no clear answers to either of those questions.

We don't even know the function of one of the most famous sleep phenomena, rapid eye movements (REMs). It's been known for decades that during certain phases of sleep, the eyes show a pattern of rapid flickering movements, and that this REM sleep is when most (but not all) dreams occur.

But what are the eye movements?

In a new paper, French sleep researcher Isabelle Arnulf sets out the case for the "scanning hypothesis". The idea is that REMs represent the dreamer "looking at" things in the dream, just like waking eye movements - at least much of the time.

Some say that REMs are nothing to do with dreams, and it's just a coincidence that they tend to occur together. They may just be random, perhaps with the function of preventing the eyes from drying out during sleep, or maybe just a side-effect of sleeping brain activity with no function at all. A possible analogy: males usually get erections during REM sleep, even though most dreams have no sexual content.

There's lots of evidence that seems to support a deflationist view of dreams. In humans and other mammals, foetuses have lots of REMs, even though they've never seen anything. Lab animals with the visual areas of the brain removed also continue to display REMs, albeit not as many of them, and people who've been blind since birth have REMs.

Anaulf disagrees however, and discusses her work with the fascinating REM sleep behaviour disorder (RBD). RBD sufferers seemingly act out their dreams. Normally, we're paralyzed during REM by an inhibitory system which causes muscle relaxation during REM. The eyes are the exception, because they have a separate nerve pathway (which is also why some otherwise paralysed people can still communicate with their eyes). RBD can be a symptom of underlying neurological disease, such as Parkinson's, but it can also occur on its own.

Anaulf's team studied 56 patients with RBD over 1 or 2 nights (Leclair-Visonneau 2010). They found that the behaviours were correlated with the onset of rapid eye movements, although 80% of the eye movements were not accompanied by any actions. What's more, out of 19 distinct behaviours (ranging from running away from lions, to strangling someone), 60% were associated with REMs, and of these 90% were in the same direction as the actions.

This directional coherence between limb, head and eye movements during RBD suggests that, when present, REMs imitate the scanning of the dream scene. Because the REMs are similar in subjects with and without RBD, we suggest the extension of this concordance to normal REM sleep.

They suggest, however, that it may not be that the eye movements are the result of the dream content, but just correlated with it. It's not that something happens on the left in the dream, and then in response, the eyes move to the left; rather it's that whatever pattern of neuronal activity causes the dream, also causes the corresponding eye movements.

Either way it's an interesting idea, although it does rely on the assumption that RBD is a good model of normal sleep in this regard.

Arnulf I (2011). The 'scanning hypothesis' of rapid eye movements during REM sleep: a review of the evidence. Archives italiennes de biologie, 149 (4) PMID: 22205589

Men, Women and Spatial Intelligence

Do men and women differ in their cognitive capacities? It's been a popular topic of conversation since as far back as we have records of what people were talking about.

While it's now (almost) generally accepted that men and women are at most only very slightly different in average IQ, there are still a couple of lines of evidence in favor of a gender difference.

First, there's the idea that men are more variable in their intelligence, so there are more very smart men, and also more very stupid ones. This averages out so the mean is the same.

Second, there's the theory that men are on average better at some things, notably "spatial" stuff involving the ability to mentally process shapes, patterns and images, while women are better at social, emotional and perhaps verbal tasks. Again, this averages out overall.

According to proponents, these differences explain why men continue to dominate the upper echelons of things like mathematics, physics, and chess. These all tap spatial processing and since men are more variable, there'll be more extremely high achievers - Nobel Prizes, grandmasters. (There are also presumably more men who are rubbish at these things, but we don't notice them.)

The male spatial advantage has been reported in many parts of the world, but is it "innate", something to do with the male brain? A new PNAS study says - probably not, it's to do with culture. But I'm not convinced.

The authors went to India and studied two tribes, the Khasi and the Karbi. Both live right next to other in the hills of Northeastern India and genetically, they're closely related. Culturally though, the Karbi are patrilineal - property and status is passed down from father to son, with women owning no land of their own. The Khasi are matrilineal, with men forbidden to own land. Moreover, Khasi women also get just as much education as the men, while Karbi ones get much less.

The authors took about 1200 people from 8 villages - 4 per culture - and got them to do a jigsaw puzzle. The quicker you do it, the better your spatial ability. Here were the results. I added the gender-stereotypical colours.

In the patrilineal group, women did substantially worse on average (remember that more time means worse). In the matrilineal society, they performed as well as men. Well, a tiny bit worse, but it wasn't significant. Differences in education explained some of the effect, but only a small part of it.

OK.

This was a large study, and the results are statistically very strong. However, there's a curious result that the authors don't discuss in the paper - the matrilineal group just did much better overall. Looking at the men, they were 10 seconds faster in the matrilineal culture. That's nearly as big as the gender difference in the patrilineal group (15 seconds)!

The individual variability was also much higher in the patrilineal society, for both genders.

Now, maybe, this is a real effect. Maybe being in a patrilineal society makes everyone less spatially aware, not just women; that seems a bit of a stretch, though.

There's also the problem that this study essentially only has two datapoints. One society is matrilineal and has low gender difference in visuospatial processing. One is patrilineal and has a high difference. But that's just not enough data to conclude that there's a correlation between the two things, let alone a causal relationship; you would need to study lots of societies to do that.

Personally, I have no idea what drives the difference, but this study is a reminder of how difficult the question is.

Hoffman M, Gneezy U, List JA (2011). Nurture affects gender differences in spatial abilities. Proceedings of the National Academy of Sciences of the United States of America PMID: 21876159