gender: biology

Flashback Friday.

Add to the list of new books to read Delusions of Gender: How Our Minds, Society, and Neurosexism Create Difference, by Cordelia Fine. Feeding my interest in the issue of sexual dimorphism in humans — which we work so hard to teach to children — the book is described like this:

Drawing on the latest research in neuroscience and psychology, Cordelia Fine debunks the myth of hardwired differences between men’s and women’s brains, unraveling the evidence behind such claims as men’s brains aren’t wired for empathy and women’s brains aren’t made to fix cars.

Good reviews here and here report that Fine tackles an often-cited study of newborn infants’ sex difference in preferences for staring at things, by Jennifer Connellan and colleagues in 2000. They reported:

…we have demonstrated that at 1 day old, human neonates demonstrate sexual dimorphism in both social and mechanical perception. Male infants show a stronger interest in mechanical objects, while female infants show a stronger interest in the face.

And this led to the conclusion: “The results of this research clearly demonstrate that sex differences are in part biological in origin.” They reached this conclusion by alternately placing Connellan herself or a dangling mobile in front of tiny babies, and timing how long they stared. There is a very nice summary of problems with the study here, which seriously undermine its conclusion.

However, even if the methods were good, this is a powerful example of how a tendency toward difference between males and females is turned into a categorical opposition between the sexes — as in, the “real differences between boys and girls.”

To illustrate this, here’s a graphic look at the results in the article, which were reported in this table:

They didn’t report the whole distribution of boys’ and girls’ gaze-times, but it’s obvious that there is a huge overlap in the distributions, despite a difference in the means. In the mobile-gaze-time, for example, the difference in averages is 9.7 seconds, while the standard deviations are more than 20 seconds. If I turn to my handy normal curve spreadsheet template, and fit it with these numbers, you can see what the pattern might look like (I truncate these at 0 seconds and 70 seconds, as they did in the study):

Source: My simulation assuming normal distributions from the data in the table above.

All I’m trying to say is that the sexes aren’t opposites, even if they have some differences that precede socialization.

If you could show me that the 1-day-olds who stare at the mobiles for 52 seconds are more likely to be engineers when they grow up than the ones who stare at them for 41 seconds (regardless of their gender) then I would be impressed. But absent that, if you just want to use such amorphous differences at birth to explain actual segregation among real adults, then I would not be impressed.

Originally posted in September, 2010.

Philip N. Cohen is a professor of sociology at the University of Maryland, College Park. He writes the blog Family Inequality and is the author of The Family: Diversity, Inequality, and Social Change. You can follow him on Twitter or Facebook.

Flashback Friday.

I heard stories this week about dung beetles and cuttlefish.  Both made me think about the typical stories we hear in the media about evolved human mating strategies.  First, the stories:

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Story #1 :The Dung Beetle

Photo from flickr by Camilo Hdo.
Photo by Camilo Hdo, retrieved from flickr.

A story on Quirks and Quarks discussed the mating strategies of the dung beetle.  The picture above is of a male beetle; only the males have those giant horns.  He uses it to defend the entrance to a tiny burrow in which he keeps a female.  He’ll violently fight off other dung beetles who try to get access to the burrow.

So far this sounds like the typical story of competitive mating that we hear all the time about all kinds of animals, right?

There’s a twist: while only male dung beetles have horns, not all males have horns.  Some are completely hornless.  But if horns help you win the fight, how is hornlessness being passed down genetically?

Well, it turns out that when a big ol’ horned male is fighting with some other big ol’ horned male, little hornless males sneak into burrows and mate with the females.  They get discovered and booted out, of course, and the horned male will re-mate with the female with the hopes of displacing his sperm.

But.

Those little hornless males have giant testicles, way gianter than the horned males.  While the horned males are putting all of their energy into growing horns, the hornless males are making sperm.  So, even though they have limited access to females, they get as much mileage out of their access as they can.

The result: two distinct types of male dung beetles with two distinct mating strategies.

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Story #2: The Giant Australian Cuttlefish

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Photo by Paul Oughton, retrieved from Flickr.

The Naked Scientists podcast featured a story about Giant Australian Cuttlefish.  During mating season the male cuttlefish, much larger than the females, collect “harems” and spend their time mating and defending access.  Other males try to “muscle in,” but the bigger cuttlefish “throws his weight around” to scare him off. The biggest cuttlefish wins.

So far this sounds like the typical story of competitive mating that we hear all the time about all kinds of animals, right?

Well, according The Naked Scientists story, researchers have discovered an alternative mating strategy.  Small males, who are far too small to compete with large males, will pretend to be female, sneak into the defended territory, mate, and leave.

How do they do this?  They change their color pattern and rearrange their tentacles in a more typical female arrangement (they didn’t specify what this was) and, well, pass.  The large male thinks he’s another female. In the video below, the cuttlefish uses his ability to change the pattern on his body. He simultaneously displays a male pattern to the female and a female pattern to the large male on the other side.

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So, can the crossdressing cuttlefish and dodge-y dung beetle tell us anything about evolved human mating strategies?

Probably not.

But I do think it tells us something about how we should think about evolution and the reproduction of genes. If you listen to the media cover evolutionary psychological explanations of human mating, you only hear one story about the strategies that males use to try to get sex. That story sounds a lot like the one told about the horned beetle and the large male cuttlefish.

But these species have demonstrated that there need not be only one mating strategy. In these cases, there are at least two. So, why in Darwin’s name would we assume that human beings, in all of their beautiful and incredible complexity, would only have one? Perhaps we see a diversity in types of human males (different body shapes and sizes, different intellectual gifts, etc) because there are many different ways to attract females. Maybe females see something valuable in many different kinds of males! Maybe not all females are the same!

Let’s set aside the stereotypes about men and women that media reporting on evolutionary psychology tends to reproduce and, instead, consider the possibility that human mating is at least as complex as that of dung beetles and cuttlefish.

Originally posted in 2010.

Lisa Wade, PhD is a professor at Occidental College. She is the author of American Hookup, a book about college sexual culture, and a textbook about gender. You can follow her on Twitter, Facebook, and Instagram.

“Future research is needed to identify the process,” write the authors, but it appears that pregnant women have some control over when they give birth. A study of birth incidence on Halloween and Valentine’s Day, by public health scholar Becca Levy and colleagues, showed that spontaneous births dipped on the former and rose on the latter.

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The authors suggest that this contributes to growing evidence that culture influences birth timing. Women’s bodies resist giving birth on a day associated with fright and death, but give into birth on a day associated with love. The authors recommend extra staffing on obstetric wards on Valentine’s Day and sending a few more doctors and nurses into the streets on Halloween.

Lisa Wade, PhD is a professor at Occidental College. She is the author of American Hookup, a book about college sexual culture, and a textbook about gender. You can follow her on Twitter, Facebook, and Instagram.

Elana M. sent along a fascinating study revealing the gender binary in our brains.  The researchers, Homayoun Javadi and Natalie Wee, asked subjects to look at a series of gendered objects — either (a) or (b) — and then judge the masculinity or femininity of a series of androgynous faces.  Gender mattered, but not how you might think.

Condition 1:1
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Condition 2:

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The findings were counter-intuitive to me.  Subjects who saw the feminine objects judged the faces to be more masculine, and vice versa for subjects who saw the masculine objects.  The researchers interpret this as an “adaptation effect,” a neurological phenomenon in which “looking at something for a long time makes you more likely to see its opposite” (source).  For example if you look at a white screen after looking at a red one for a while, the white screen will appear green (red’s opposite).  Or, if you look at lines moving right for a while and then look at static lines, they will appear to move left.

Javadi and Wee’s findings suggest that our brains give gender to both objects and people and that we place masculinity and femininity in a binary.  We are “opposite sexes,” then, but only in our minds.

Lisa Wade, PhD is a professor at Occidental College. She is the author of American Hookup, a book about college sexual culture, and a textbook about gender. You can follow her on Twitter, Facebook, and Instagram.

Screenshot_5One of the few genuinely large observed differences between men and women involves throwing ability.  Men, on average, are much stronger throwers than women.  Hence the phrase “throws like a girl.”

That we observe a difference, however, tells us nothing about where that difference comes from.  Figuring that out is much more difficult than simply measuring difference and sameness.  We know that the difference emerges at puberty, suggesting that sheer size might have something to do with it.  But the fact that boys and men, on average, get much more practice throwing than women might also play a role.  How to test this?

Well, here’s one way: compare men and women throwing with their non-dominant hand.  Muscle memory doesn’t transfer from one side of the body to the other.  Accordingly, since most people have a lot of practice throwing only with one hand, comparing the throws of men and women using their non-dominant hand might tell us something interesting.

I don’t know that that study has been done, but an enterprising videographer has captured video of a set of men throwing with the “wrong” hand. What I like most about the video is the men’s facial expressions.  You can see them laughing at themselves, suddenly reduced to a beginner thrower.  Though we still don’t know how much of it is biological and how much social — though, this is the wrong question anyway — it reveals that, no matter what the answer, men’s throwing ability is strongly related to practice:

A big thanks to Reynaldo C. for sending in the video!

Cross-posted at BlogHer.

Lisa Wade, PhD is a professor at Occidental College. She is the author of American Hookup, a book about college sexual culture, and a textbook about gender. You can follow her on Twitter, Facebook, and Instagram.

Cross-posted at Ms. and the Huffington Post.

I loathe to weigh in on the “war on men” conversation, but… alas.

While one can use both logic and data to poke gaping holes in Suzanne Venker’s argument that women need to surrender to their femininity and let men think that they’re in charge if they ever want to get married, I just want to point out one thing — one endlessly repeated thing — that she gets very, very wrong.

Venker claims that there has “been an explosion of brain research” that proves that men and women have different brains.  This research, she claims, shows that men are loners who like to hunt and build things and women are nurturers who like to talk and take care of people.

This false on two fronts.

First, she’s wrong about the brain research.  The books and articles claiming that there are “pink” and “blue” brains are not consistent with existing research.  (They are out there because people can make a lot of money by confirming other people’s biases.)

What does the research say?

It’s true that scientists have documented a number of small, average sex differences in brain anatomy, composition, and function, as well as differences in size and tissue ratios.  (Other differences — such as the size of the corpus callosum and lateralization, whether one sex uses one side of their brain more than the other — have proven to be wrong.)

So, scientists do find some differences, but they have largely failed to link these to differences in men’s and women’s observed emotions, cognition,  or behavior.  That is, we’ve found some differences, but we have no proof that they translate into anything. Moreover, new research suggests that differences we observe may be designed not to create differences between men and women, but to reduce them.  The brain may have two strategies for achieving the same outcome or one difference may compensate for another.  (For more, see Brain Gender by Melissa Hines.)

That’s one reason why Venker is wrong.

The second reason is even more damning.  Most of the research attempting to explain gender difference assumes that there differences to explain.   In fact, meta-analyses aimed at summarizing the literature on human sex differences and similarities in traits, personality, cognitive abilities, sexuality, temperament, and motor skills offer better evidence for similarity than difference.  On the vast majority of traits, men and women overlap tremendously.

Janet Hyde, a pioneer in this area, did a meta-analysis of meta-analyses that combined the results of 7,084 separate studies. She found evidence for a large or very large difference on 8% of characteristics and evidence for medium-sized differences on 15%.  She found evidence for small differences on another 48%.  What does a small difference look like?  Here’s an example of a mid-range small difference (for self-esteem):

For the final 30% of characteristics, she found no evidence gender difference.  So, on 78% of characteristics, she found teensy differences or none at all.  Wow, “opposite sexes” indeed.

The truth is, men aren’t loners and women aren’t talkers. Venker assumes the stereotypes and counts on her readers to agree that they are true, but the data doesn’t back her up.

Two excellent books summarize the debates over gender and neuroscience.  Cordelia Fine’s Delusions of Gender is great for a beginner. She’s funny and you’ll learn a lot. Rebecca Jordan-Young’s Brain Storm is great for someone who wants and intermediate to advanced introduction to these issues.  Her book is downright brilliant.  I highly recommend both.

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Lisa Wade is a professor of sociology at Occidental College.  Feel free to take a look at her forthcoming article, “The New Science of Sex Difference.”  You can also follow her on Twitter and Facebook.

The term sexual dimorphism refers to differences between males and females of the same species.  Some animals are highly sexually dimorphic. Male elephant seals outweigh females by more than 2,500 pounds; peacocks put on a color show that peahens couldn’t mimic in their wildest dreams; and a male anglerfish’s whole life involves finding a female, latching on, and dissolving until there’s nothing left but his testicles (yes, really).

On the spectrum of very high to very low dimorphism, humans are on the low end.  We’re just not that kind of species.  Remove the gendered clothing styles, make up, and hair differences and we’d look more alike than we think we do.

Because we’re invested in men and women being different, however, we tend to be pleased by exaggerated portrayals of human sexual dimorphism (for example, in Tangled). Game designer-in-training Andrea Rubenstein has shown us that we extend this ideal to non-human fantasy as well.  She points to a striking dimorphism (mimicking Western ideals) in World of Warcraft creatures:

Annalee Newitz at Wired writes:

[Rubenstein] points out that these female bodies embody the “feminine ideal” of the supermodel, which seems a rather out-of-place aesthetic in a world of monsters. Supermodelly Taurens wouldn’t be so odd if gamers had the choice to make their girl creatures big and muscley, but they don’t. Even if you wanted to have a female troll with tusks, you couldn’t. Which seems especially bizarre given that this game is supposed to be all about fantasy, and turning yourself into whatever you want to be.

It appears that the supermodel-like females weren’t part of the original design of the game.  Instead, the Alpha version included a lot less dimorphism, among the Taurens and the Trolls for example:

Newitz says that the female figures were changed in response to player feedback:

Apparently there were many complaints about the women of both races being “ugly” and so the developers changed them into their current incarnations.

The dimorphism in WoW is a great example of how gender difference is, in part, an ideology.  It’s a desire that we impose onto the world, not reality in itself.  We make even our fantasy selves conform to it.  Interestingly, when people stray from affirming the ideology, they can face pressure to align themselves with its defenders.  It appears that this is exactly what happened in WoW.

Lisa Wade, PhD is a professor at Occidental College. She is the author of American Hookup, a book about college sexual culture, and a textbook about gender. You can follow her on Twitter, Facebook, and Instagram.

Evolutionary psychologists argue that when we find certain traits sexually attractive in others it may be because they signal reproductive fitness.  It goes something like this: People who have been sexually attracted to traits that tell the “truth” about genetic superiority have been more likely to choose mates with superior genetics and, therefore, have been more likely to produce healthy offspring that live to an age where they, in turn, can reproduce themselves.  Accordingly, nature has selected for individuals attracted to people who display signs of genetic excellence.

Culture throws a wrench in this theory because human can create their own systems of meaning, collectively convincing each other that certain traits are desirable regardless of the relationship between the trait and reproductive fitness.  The thinness ideal for women is an excellent example.  Judging by pop culture, heterosexual men have a strong preference for very thin women.  In fact, however, the weight idealized in mass media is not conducive to reproductive fitness; women won’t ovulate or menstruate below a certain weight because their body recognizes that it can’t support a pregnancy.

A new study — by Leigh Simmons, Marianne Peters, and Gillian Rhodes — offers another tantalizing piece of information regarding the relationship between attractiveness and reproductive fitness.  Pre-existing research shows that men with lower voices are judged more sexually attractive, so the authors decided to measure one indicator of their reproductive fitness, sperm count.

The results? Voice attractiveness is related  to sperm count, but in the opposite direction expected.  Men with higher voices, in fact, have higher sperm concentration, not lower.

The jury is still out about what this means, but it’s an intriguing addition to the ongoing conversation that social and biological scientists are having about how culture and nature interact to shape human experience.

Lisa Wade, PhD is a professor at Occidental College. She is the author of American Hookup, a book about college sexual culture, and a textbook about gender. You can follow her on Twitter, Facebook, and Instagram.