Summer of the pill: Will the pill mess up my ability to detect my One True Love?

Should I advise recently single ScarJo to stay
off the pill to find her next beau? From here.

Imagine you are a single, heterosexual woman. You meet a nice man at the driving range, or on a blind date. You like him and he likes you. You date, you get engaged, you get married. You decide to have a child together, so you go off the pill. One morning you wake up and look at your husband, and it’s like seeing him through new eyes. Who is this stranger you married, and what did you ever see in him?

After some articles made the news when they suggested mate preferences change on hormonal contraception, this seemed to be the scenario in the heads of many women. Is my pill deceiving me? What if my birth control is making me date the wrong man?

Several articles over the years have demonstrated that women prefer men with more masculine features at midcycle, or ovulation, and more feminine features in less fertile periods. Based on body odor, women and men also often prefer individuals with MHC (major histocompatibility complex) that are different from theirs, which may be a way for them to select mates that will give their offspring an immunological advantage. These findings have been replicated a few times, looking at a few different gendered traits. And as I suggested above, other work has suggested that the birth control pill, which in some ways mimics pregnancy, may mask our natural tendency to make these distinctions and preferences, regarding both masculinity and MHC (Little et al. 2002; Roberts et al. 2008; Wedekind et al. 1995).

On the one hand, I think it’s both interesting and important to consider the implications of the birth control pill beyond just contraception. Hormones are messages, so any cells that have receptors for these messages, like specialized mailboxes, can receive them. The pill is made of synthetic versions of estradiol and progesterone, and there are estradiol and progesterone receptors in your brain. And yes, these hormones do change your brain, both during the natural cycle and on hormonal contraception; Scicurious has written well on this in the past.

Jolie, had she been on the pill and chosen her mate
differently. From here. Yes, looks to be a real pic.

On the other hand, I have a lot of questions: First and most important to me, how does any of this translate to non-straight women? I find the constant focus on mate choice between men and women a bit exhausting, and am not sure we can assume non-straight relationships to work the same way. Next, how well do preferences over the cycle map on to actual choices for mates, short term or long term? If we happen to find Brad Pitt more attractive than Justin Bieber at midcycle, does that mean no one will do but Brad Pitt? And finally, what are all the factors that we need to consider in mate choice besides a deep voice or square jawline (again, especially if you try to expand your thinking beyond straight relationships)?

I’ll start with the last two questions that deal with mate preference versus ultimate mate selection. As you all might expect, women and men choose mates for lots of reasons, not just masculinity or complementary immune systems. Bereczkei et al (1997) looked at singles ads and found women often sought mates with high parental care. In a separate singles ad evaluation, Pawlowski and Dunbar (1999) found that women mostly selected men of high resource potential who were interested in long-term relationships (either unlikely to divorce or unlikely to die within twenty years), where men selected women by markers of fecundity (ability to have babies). In a sample of 18-24 year old straight people in the US, Buston and Emlen (2003) found that most people selected mates who had similar characteristics to themselves. And a speed dating sample showed that people under those conditions selected dates based on easily observable traits, like physical attractiveness (Kurzban and Weeden 2005).

Now on to the fact that all of this research is on straight people. I found very little on lesbian women and the menstrual cycle... but what I found was very cool! Brinsmead-Stockham et al (2008) found that, like heterosexual women, lesbian women are quicker to identify unknown faces at midcycle, as long as they were the faces of the sex they preferred. So straight women were good at identifying male faces, lesbian women good at identifying female faces. Burleson et al (2002) found that sexual behavior in lesbian and straight women was mostly similar through the menstrual cycle, with both peaking at midcycle.

So, mate preference may be about telling a research assistant who is the hottest to you at a particular point in your cycle. And it is a fairly robust and consistent finding. However, when it comes to ultimate mate selection the most important thing to consider is a great point made by Pawlowski and Dunbar: finding a mate is about advertising what you have to offer while making known what you want in a mate. Then it’s all about finding some kind of compromise through a series of trade-offs based on what the individual wants, what they can offer, and what’s available in the dating pool. (So, since neither Brad Pitt nor Justin Bieber are currently in the dating pool, my previous comparison was pointless.)

Those of you who met your mate while on the pill: not to fear. I don’t think that the possibility that you may have some suppression of masculinized preferences at one point in your cycle means you’ve chosen the wrong person.

Who knows, it could have opened you up to the Mr. or Ms. Right.

References
Bereczkei T, Voros S, Gal A, & Bernath L (1997). Resources, attractiveness, family commitment; reproductive decisions in human mate choice. Ethology : formerly Zeitschrift fur Tierpsychologie, 103 (8), 681-99 PMID: 12293453

Brinsmead-Stockham K, Johnston L, Miles L, & Neil Macrae C (2008). Female sexual orientation and menstrual influences on person perception Journal of Experimental Social Psychology, 44 (3), 729-734 DOI: 10.1016/j.jesp.2007.05.003

Burleson MH, Trevathan WR, & Gregory WL (2002). Sexual behavior in lesbian and heterosexual women: relations with menstrual cycle phase and partner availability. Psychoneuroendocrinology, 27 (4), 489-503 PMID: 11912001

Buston PM, & Emlen ST (2003). Cognitive processes underlying human mate choice: The relationship between self-perception and mate preference in Western society. Proceedings of the National Academy of Sciences of the United States of America, 100 (15), 8805-10 PMID: 12843405

Kurzban R, & Weeden J (2005). HurryDate: Mate preferences in action Evolution and Human Behavior, 26 (3), 227-244 DOI: 10.1016/j.evolhumbehav.2004.08.012

Little AC, Jones BC, Penton-Voak IS, Burt DM, and Perrett DI. 2002. Partnership status and the temporal context of relationships influence human female preferences for sexual dimorphism in male face shape. Proceedings of the Royal Society of London Series B: Biological Sciences 269(1496):1095-1100.

Pawłowski B, & Dunbar RI (1999). Impact of market value on human mate choice decisions. Proceedings. Biological sciences / The Royal Society, 266 (1416), 281-5 PMID: 10081164

Roberts SC, Gosling LM, Carter V, & Petrie M (2008). MHC-correlated odour preferences in humans and the use of oral contraceptives. Proceedings. Biological sciences / The Royal Society, 275 (1652), 2715-22 PMID: 18700206

Wedekind C, Seebeck T, Bettens F, & Paepke AJ (1995). MHC-Dependent Mate Preferences in Humans Proceedings: Biological Sciences, 260 (1359), 245-249 DOI: 10.1098/rspb.1995.0087

Around the web: belated mother's day edition

Apologies for the re-post, it was the only way to save the post and comments with the correct tags after the Blogger meltdown the other day!

I've been accumulating a lot of mother-y links lately, thought I would share. First two Mother's Day columns that remind us that we shouldn't just put Mom on a pedestal and give her some chocolate one day a year, but think in a more systematic way about the oppression of women and children worldwide. Read this one by Esther Cepeda, and this one by Nicholas Kristof.

Fertility

Women see Georgia O'Keefe art as erotic around ovulation. I'm not sure this really qualifies as evolutionary psychology, or needs that framework to understand that libido is higher near ovulation, which would increase the chances one would find erotic art extra erotic at that time.

Birth

Chimps give birth like humans. Very cool. I guess we didn't notice until now because they are so solitary when they birth?

Cesarean sections are a major factor in maternal death. I don't like how this article seems to blame the mother, given the way interventions seem to shunt many women towards C-sections whether they want one or not. But there are certainly many factors to consider in this issue, including the mother's past health and the kinds of protocols used at the location where she is giving birth.

Cutting the cord too soon. This is an interesting piece in Time about the timing of cord clamping and its impact on respiratory issues in infants. Many birth centers and hospitals are advocating for a later time to clamp the cord for this and other reasons.

Mothering of all kinds

Hope for teenage mothers. This was a great story about a great program to help teen mothers have more success in school and beyond.

The amount of time a woman breastfeeds is related to her race and income. Not surprising, given that lactation support services are probably harder to come by, and that women who must earn an income can't necessarily afford to go without pay for twelve weeks (that is the minimum maternity leave we get in the US, based on the Family Medical Leave Act, and most places give only that minimum). Even those women who do manage to get into a rhythm with breastfeeding lose it when they return to work, not just because of those short twelve weeks, but because few employers have workplaces set up for pumping.

Amy Poehler's acceptance speech at the Time 100. She discusses the many other women (dare I say allomothers?) who support her as she raises her children and has a career. I may have teared up a little. Okay, I shut my office door and cried.

What measles vaccine refusal really costs. This is something parents should care about.

A hilarious account from a father about all the things you need to worry about -- and expect to be judged upon -- when having a child.

Finally, while this went around the interwebs when Dr. Isis wrote it the first time, re-read her AGORA post about why it's all right to not be your mother.

Miscellaneous ladybusiness

The enduring gender gap in pay. Sigh.

Michele Bachelet should be everyone's hero, if what I read in this story is any indication.

We can no longer escape the reality that BPAs (and other associated bisphenols, which unfortunately are what are being replaced in plastics that claim to be BPA-free) are endocrine disruptors that have negative consequences for health. Well, unless you're Coca Cola. Then you are going to put your fingers in your ears and go "lalala!"

A lovely post on feminist reactions to street harassment. Another, very powerful read: kill me or leave me alone.

An important read about the use of language in journalistic storytelling, and the sexist way the New York Times originally covered the brutal gang rape of a little girl.

Historic STD posters. Were some sexist? Of course. But it only makes me want one for my office more, if for its ironic value.

Do girls steal some of their mother’s beauty? Sex bias in parental investment

Sons and daughters and differential parental investment

One of my favorite rhetorical tricks is asking my students a question that has an obvious answer based on cultural expectations, but is wrong. So every year, when I start to teach my students about parental investment, I ask:

Who is harder to raise, sons or daughters?

I’ve asked by a show of hands and with iClickers, over the years, and the room of 750 is almost unanimous: daughters are harder to raise. So, then I get off the stage and walk around a bit. What do you mean by that? I ask.

Girls cause more gray hairs.
Girls cause more trouble when they start to like boys.
Girls are more work, and cost more money, since they shop all the time.
Girls talk back more.

And of course, there is always the saying that girls steal some of their mother’s beauty.
So then I show them this:

From Helle et al 2002.

Here is a graph of maternal longevity based on the number of sons or daughters they have. This data was based on a historical population from Finland from 1640-1870 using church records (Helle et al 2002). As you can see, the more sons mothers bear, the shorter their lifespans. You see the opposite for daughters. So sons have a negative impact, and daughters have a positive impact. This same trend has been found in records from a Flemish village (van de Putte et al 2003, 2004), where sons negatively impact lifespan but not daughters. Interestingly, data from church records from the field site where I work in rural Poland provides a slightly different picture: every offspring of either sex reduced lifespan by about 95 weeks (Jasienska et al 2006).

From Jasienska et al 2006.

Once students see these graphs, they quickly realize what is going on. Generally speaking, girls help mothers more at home in terms of chores and alloparenting. And in many cultures, particularly the historical ones studied so far, sons are costly because parents invest more in them, to help launch their own families. Daughters, not so much. In the Polish population, there may be other factors where daughter investment is important, or it is just costly to have so many offspring and you have maternal depletion regardless of daughter help.

Sex bias in parental investment is an important part of understanding both the biology and culture of parenting, and the developmental trajectories of children. The Trivers-Willard hypothesis, which has been tested many times in humans and animals, suggests that parents should invest more in sons when conditions are good, and more in daughters when conditions are bad. That is, when you have lots of resource you should put it towards a son in order to increase the chances he will have high reproductive success, since his is assumed to be more variable and high effort could lead to high reward. But in periods of low resource, daughters are a good bet because they are more likely to have at least some reproductive success no matter what.

From Hrdy 1990.

Of course, differential investment based on resources is further conflated in humans due to culture and, I would contend, our almost universal favor for patriarchy (Smuts 1995). Here is an image of an Indian family waiting at a clinic. There is a mother, an older son, and a twin boy and girl. Notice the extreme difference in health between the infant boy and girl – they are twins, yet the infant girl is emaciated. This is because in this population sons are always fed and cared for first, and whatever is left over, if there’s anything, is given to daughters.

So, parental investment can have real effects on the parent in terms of lifespan, and perhaps also their own future reproductive capabilities. Further, the conditions under which you may have children can vary, but how much a parent chooses to invest in their children varies too.

The piece of this that may be toughest to parse out, particularly in humans, is how the condition of the mother (or parents) can vary, and how that variation impacts the sex ratio of their children. In some species, like red deer, it is easier to imagine a mechanism: these animals have diapause, a period where their embryos are dormant until it is a good time to gestate and bear them. It is easier to insert some kind of selection process into a period where several embryos are all “frozen” and sex has been determined. But what about humans that produce singletons and invest huge, overlapping amounts of support to their children over decades? How would a sex bias based on maternal condition operate? And is there anything the offspring can do about it?

Changes in maternal breast size during pregnancy

It turns out that measurements as easy as stepping on a scale, and knowing your bra size, can begin to unpack the answer. First, a confession: I consider the author of this paper Andrzej Galbarczyk more than a colleague, but a friend. Andrzej is the graduate student who oversaw my Polish field site last season (Mogielica Human Ecology Study Site, director Dr. Grazyna Jasienska). He has translated consent forms and surveys for me and we’ve had many valuable and important conversations about my fieldwork. He is a smart, kind and thoughtful person and scholar. So, I let him see an early draft of this post to make sure I understood his point of view.

Galbarczyk performed an internet survey in Poland with 120 women, where he asked them to report their pre-pregnancy weight and bra size, their bra size directly after giving birth, and the sex of their offspring. He found two notable differences in these women: mothers of daughters weighed less before pregnancy, but had a greater changes in breast size during pregnancy.

The evidence about maternal pre-pregnancy weight is consistent with the Trivers-Willard hypothesis, as mothers who had sons were more likely to be heavier, and thus have more resource to invest. The second significant difference, that mothers with daughters had larger breasts after pregnancy, seems could be argued either way: Galbarczyk argues that it supports Trivers-Willard because mothers of sons could have been devoting more resource to growing their offspring rather than their breasts.

In other animals and primates particularly, mothers of male infants produce more energy-dense milk, yet mothers of female infants may produce a greater quantity of milk (Hinde 2009). And breast size is a pretty noisy signal of milk quality or quantity. So, what is the meaning of this difference in breast size?

Adaptation or physiological inevitability?

Galbarczyk suggests the difference is related to the evolutionary underpinnings of human female breasts. Women develop breasts around puberty, and though they certainly change in size and shape over time, keep them their whole lives. Other animals develop their mammary glands only shortly before lactating and then they regress again. Many contend that human breasts are an honest signal of fertility. This is at least partially confirmed by the correlation between breast size and estradiol concentrations (Jasienska et al 2006).

Galbarczyk thinks that the larger breasts seen in postpartum mothers to daughters may be a way to attract a mate for parental care. Perhaps this would help where she has given birth to the less-favored sex and needs to really convince him to participate; this could be a signal from the mother or the female fetus. Or maybe by appearing more attractive, she can have another reproductive opportunity, which would give her a chance to have a son.

You all know how I feel about evolutionary storytelling. In certain ways I do find this particular argument compelling, from the perspective of the Trivers-Willard hypothesis. But the evidence for the adaptive scenario around breast size is circumstantial.

Also, I don’t want this story to detract from some very interesting data: remember that Galbarczyk found that in this population, mothers of daughters weigh less before pregnancy, and develop larger breasts afterwards. Very cool. So perhaps we should consider a mechanistic, rather than adaptive explanation?

I have two thoughts about this, both related to androgens (androgens are the class of hormone that testosterone falls under). First, I wonder if there is an effect of fetal androgens from a male fetus on breast size. If so, mothers of daughters would have larger breasts simply because they aren’t having their breast tissue growth or density suppressed by androgens. It could simply be physiology that doesn’t have adaptive meaning.

Second, the mothers of sons were heavier before pregnancy. Heavier individuals tend to have higher circulating insulin levels, and the ovary can respond to higher insulin by producing more androgens (Poretsky 1991, Dimitrakakis et al 2004). So you could have a suppressive effect on breast size from that avenue as well. You don’t need an adaptive scenario for either of these mechanisms, just a consequence of how hormones work.

I would love to see Galbarczyk or someone else follow up on these thought-provoking results by measuring women, rather than relying on self-report, and by measuring their estradiol, progesterone and androgens. Understanding the different factors and motivations that lead to sex differential investment and outcome is a great field of study, and this work gets us thinking in a new direction.

References

Dimitrakakis C, Jones RA, Liu A, & Bondy CA (2004). Breast cancer incidence in postmenopausal women using testosterone in addition to usual hormone therapy. Menopause (New York, N.Y.), 11 (5), 531-5 PMID: 15356405

Galbarczyk A (2011). Unexpected changes in maternal breast size during pregnancy in relation to infant sex: An evolutionary interpretation. American journal of human biology : the official journal of the Human Biology Council PMID: 21544894

Helle, S. (2002). Sons Reduced Maternal Longevity in Preindustrial Humans Science, 296 (5570), 1085-1085 DOI: 10.1126/science.1070106

Hinde K (2009). Richer milk for sons but more milk for daughters: Sex-biased investment during lactation varies with maternal life history in rhesus macaques. American journal of human biology : the official journal of the Human Biology Council, 21 (4), 512-9 PMID: 19384860

Hrdy, S. (1990). Sex bias in nature and in history: A late 1980s reexamination of the “biological origins” argument American Journal of Physical Anthropology, 33 (S11), 25-37 DOI: 10.1002/ajpa.1330330504

Jasienska G, Nenko I, & Jasienski M (2006). Daughters increase longevity of fathers, but daughters and sons equally reduce longevity of mothers. American journal of human biology : the official journal of the Human Biology Council, 18 (3), 422-5 PMID: 16634019

Poretsky L, Seto-Young D, Shrestha A, Dhillon S, Mirjany M, Liu HC, Yih MC, & Rosenwaks Z (2001). Phosphatidyl-inositol-3 kinase-independent insulin action pathway(s) in the human ovary. The Journal of clinical endocrinology and metabolism, 86 (7), 3115-9 PMID: 11443175

The Scorpion and the Frog: don't try and tell me why I do this

On April 8th, I was fortunate to be in the company of Matt Richtel, Scott White, Diana Yates and Dan Simons as part of a talk and panel discussion sponsored by the Beckman Institute and the College of Media at the University of Illinois. Matt Richtel is a Pulitzer prize-winning journalist for the New York Times who has written on distracted driving, your brain on computers, and, as many of you know, neuroscientists on a raft. Matt also writes a comic and has published two works of fiction. It was a pleasure getting to know a journalist so committed to respecting scientists and getting the story, and the science, right.

Matt began the event with a short, engaging talk on the interaction between scientists and journalists. He started with the fable of the scorpion and the frog, yet never quite resolved for the audience whether he saw the scorpion as the journalist or scientist. He shared several experiences with scientists who were uninterested in talking to the press, some who pushed him to add complexity or uncertainty to a story, and some who managed to convey simple, compelling ideas in their quotes. I want to briefly describe what he said about these three populations.

For those uninterested in talking to the press, Matt suggested that, for some, this may be due to a distrust of the press, or fear of how one will be represented to colleagues. He described a time that a female scientist agreed to talk to him, on the condition of not having her picture taken for the story. She was a former model, she explained, and didn’t want her image associated with her science, lest her colleagues take her less seriously. Unfortunately, I think there are plenty of fields where this is a legitimate issue, if past issues in the science blogosphere are any indication. That said, I think he makes a good point that while you do take a risk in talking to the press, and there may be times where your work isn’t perfectly represented (and even times where it is grossly misrepresented), most of our colleagues know not to just blame the scientist. Besides, if you have a colleague that is that punitive, they aren’t a very good colleague!

Matt told a story about a scientist who worked with him on a piece, then backed out and asked that all of his material be removed. Over the course of a difficult conversation, the scientist revealed his fear that his colleagues would judge his quotes as overstating the results of the evidence. Eventually, they worked out an alternative quote that simply added in a qualifier (I believe it was the word “almost” but I don’t remember). Keeping the qualifier, or pushing for its inclusion, can satisfy a lot of scientists talking to the press, and in doing so it adds a necessary element of uncertainty. The scientific method s not about proving things, it is about disproving them. You want to disprove the null hypothesis (an example of this would be that your hypothesis is that estrogen varies with lifestyle, and the null hypothesis is that there is no difference in estrogen based on lifestyle). And, when you get evidence that supports your hypothesis, this doesn’t prove a thing. All it does is support the hypothesis in the context of that particular study’s parameters. Given this understanding of the scientific method, perhaps journalists could see how much scientists chafe at bold conclusions or words like “proof” or “fact!”

Finally, Matt described a class of scientists who are not only good to work with, but provide statements that convey complex ideas in an engaging, easy to understand way. He calls these scientists Quote Monkeys. Quote Monkeys not only distill a difficult idea for a lay audience, yet convey excitement and delight in science. He used the example from his “your brain on computers” series where one scientist said “Bring back boredom!” This captures the idea that not multi-tasking all the time, that having downtime to process events rather than always being plugged in, is good for our brains. (So, if you’re reading this on your phone in the bathroom, put the phone down. You know who you are!)

After Matt’s wonderful talk, Scott, Diana and I served as panelists, with Dan Simons moderating. Scott White is a professor in Aerospace Engineering who has had some media attention for his supercool self-healing materials. I appreciated his approachable, dry style. Diana Yates is a journalist who covers the life science beat for the University of Illinois News Bureau, and she has done an amazing job over the years showing the rest of the world why the science that happens here at Illinois is so exciting. Dan Simons co-authored a great popular science book The Invisible Gorilla (I bought it for my brother in law this past winter before I realized Dan was on campus), and has a social media presence as well, curating interesting material mostly on cognitive psychology. We each gave a little introduction to ourselves regarding our experiences with journalists; I largely talked about how social media is what has connected me to science journalists, and my experiences with CNN.com and USA Today writers (both positive).

The questions we received were good ones, ranging from how to keep from looking like a fool while talking to journalists to how to write science stories without resorting to clichés or self-help hooks. For the first issue, we discussed the importance of asking a journalist for her/his timeline (is your story due in 20 minutes, hours or days?) and that one should request seeing the quotes that will be used before the story goes live. You also don’t have to say yes to every request; if the timeline is too short or you have looked up the journalist and they or their employer aren’t reputable, just move on. For the second question, I talked about reframing the question that captures the audience’s interest from “how does this affect me?” to “why should I care?” or “why is this cool?” I mentioned Ed Yong as an excellent example of a writer who delights the reader, regardless of whether he is discussing algae, racism, or bat fellatio. He shares his excitement and is a guide, not a sage; I think Ed’s work is compelling for the same reasons NPR’s Radiolab is so good. You get the sense the narrator is learning along with you, though in Ed’s case I think you also get the sense that he has scientific expertise to add credibility to his analysis and what he chooses to cover.

One audience member made a rather bold, critical claim that journalists and scientists were in cahoots to promote the journalists and get the scientists tenure. The other panelists handled this one delicately. I did not (what, you are surprised?). Academic readers of this blog are likely aware that writing a blog is a professional risk, as is talking to journalists, especially when one is a junior faculty member. As John Hawks said in his panel on blogging in the academy at Science Online 2011, blogging is at best a tertiary activity. But if you use your blog not only to reach out to layfolks but also to make broader claims about your field, you may have critics as well as fans. I know the risks I take every time I put up a new blog post or agree to talk to a journalist. But I have also decided that my enjoyment, and the benefits to my own goals of scientific outreach, far outweigh the risks. I want women to read my posts and pass them on to their daughters. I want readers of sites like Jezebel and Feministe getting excited about biology. And I want every person who has found evolutionary psychology claims intuitive to think on the bias that produces that false intuition.

When I was a child, my parents had the following Man of La Mancha quote in our bathroom, on a poster directly opposite the toilet:

Too much sanity
May be madness
But the maddest of all
Is to see life as it is
And not as it should be.

I learned to read with that quote. I sang it in my head. And when I was younger, it meant absolutely nothing to me. I don’t remember the moment exactly when it went from something I chanted in my head to something that defined my own outlook on the world. But I want to make this job into the job it should be, not the job it is. To me, that means blogging, talking to laypeople about science, and interacting with science communicators and journalists.

But don’t tell me I do it to get tenure.

If I objectify you, will it make you feel bad enough to objectify yourself? On shopping, sexiness and hormones.

Found here.

When I was younger, periods were not a fun time, and I was plagued with dysmenorrhea, which is a fancy term for really bad cramps. In high school, I would often take 1000 mg of ibuprofen every four hours to alleviate symptoms to get through all my classes, band, sports practice, and homework (what, it took you this long to realize I was, and am, a dork?).

After having my daughter in 2008, and the thirteen months of lactational amenorrhea that followed it (lactational amenorrhea means absence of periods due to lactation), my periods resumed. Pain during my periods has almost totally ceased, but I have noticed more cycle-related variation in emotion. In particular, my patience and tolerance for rude behavior, and my tendency to cry sentimentally at even the lamest greeting card, skyrocket in my premenstrual phase. I already have low tolerance for rudeness, and I already cry easily. But something about progesterone decline -- which is a normal process towards the end of ovulatory cycles -- seems to make it harder for me to repress these behaviors in order to fit in culturally with those around me.

I tell this to you to say, I don't doubt that hormones, and hormonal variation through the cycle, plays some role in variation in female behavior and emotion. And I find this kind of work inherently interesting. I hate to repeat myself, but you will find echoes of my structural and methodological concerns with evolutionary psychology in this post as well.

* * *

Durante et al (2011) observe that women spend more money on their appearance than men, and claim that this sex difference is cross-culturally consistent (I wonder, is this consistent across cultures without money?). In order to understand this sex difference, they wish to see whether spending or shopping behavior is dependent on cycle phase. Therefore the authors hypothesize that women choose sexier clothing during ovulation -- "even if the women themselves are not consciously aware of this biological fact" (Durante et al 2011: 922), a problematic turn of phase if I ever saw one, but I'll get to that later. They also consider the effects of priming a shopping woman with images of attractive women and hypothesize there is a greater effect of this priming on high-fertility women.

Methods

The participants were female undergraduates and were compensated with course credit or money. The authors claim the participants had no idea the study had anything to do with the menstrual cycle, but the participants had to use LH strips at midcycle to see when she was ovulating (this is a urine test to check for a luteinizing hormone peak, which comes before ovulation).

Here's the important part, for me:

"The first urine test was scheduled 2 days before the expected day of ovulation. If an LH surge was not detected, women came back each day until an LH surge was detected or six tests had been completed, whichever came first" (Durante et al 2011: 924).

Here are my questions: what is 2 days before the expected day of ovulation? The follicular phase -- that's from menstruation to ovulation -- is the most variable phase of the menstrual cycle (Fehring et al. 2006; Lenton et al. 1984). I wonder how many ovulations they missed because of this. Perhaps even worse, how many participants had six LH tests and didn't have a detectable LH surge? It sounds like they were included in the project. But, they either ovulated before the authors started testing, or they had an anovulatory cycle. That means the authors were including participants in their study that weren't ovulating... in a study of behavior during ovulation.

Participants viewed a made-up shopping website on a high-fertility (near the LH surge) and low-fertility (about eight days later) day, where they had to select ten items they would like to buy that day. They were randomized into two groups: one shown a site featuring casual clothes, the other featuring clothes and accessories. The clothing on these made-up sites were "pretested to be sexy" (Durante et al 2011: 925). While that is a phrase I never expected to write on this blog, the separate validation they did to determine sexy versus nonsexy clothing seems fine.

Results

Hypothesis 1: Near ovulation, women should be more likely to choose sexier and revealing clothing and other fashion items rather than items that are less revealing and sexy (Durante et al 2011: 923).

Women chose a greater percentage of sexy clothing and accessory items near ovulation: 59.8% ± 21.6 during ovulation, 51.3% ± 22.4 during low fertility. This was a statistically significant difference, but they did a repeated measures ANOVA, and I don't understand why they didn't do a paired t-test. Further, statistically significant or not, I question how meaningful it is when the averages are so close and the standard deviations almost completely overlap.

H2: Ovulation should lead women to be especially likely to choose sexier products when women are primed to compare themselves to attractive female rivals (Durante et al 2011: 924).

H3: There should be no differences in product choice between ovulating and nonovulating women when women are primed with unattractive women or men (Durante et al 2011: 924).

Follow-up studies primed sub-sets of participants (so a different cohort, same recruitment methods as above) to think about 1) attractive local women, 2) unattractive local women, 3) attractive local men, 4) unattractive local men. They did this by showing photographs of people who they claimed to be local and asking participants to rate their attractiveness.

When primed with attractive women, the percentages of sexy items chosen were 62.7% for ovulating women and 38.2% for low fertility women (I could not find standard deviations for these values so have no idea how much the two groups overlap). Priming with unattractive women, attractive men, or unattractive men produced no significant difference between low and high fertility women.

H4: Ovulation should lead women to choose sexier products when primed to think about local attractive women who constitute potential direct rivals. However, ovulation should not influence product choice when women are primed to think about women from distant locations because such women do not constitute direct rivals (Durante et al 2011: 924).

The authors used a different method for assessing fertility this time; they asked women their normal menstrual cycle length and counted back from menses to estimate when ovulation would be. So AGAIN, we don't know how many women actually ovulated in this study, and we don't know whether a significant portion of women were then grouped in the high-fertility group who shouldn't have been.

This study is like the previous one in terms of photo priming, but this time the photos were said to be local or distant, and were of women only (so the four groups were local attractive, local unattractive, distant attractive, distant unattractive).

The authors claimed that the relationship between fertility, photo attractiveness and location was "marginally significant," but the p-value was 0.09. That is, in fact, not significant, as significance is generally only considered under 0.05 unless you cheat and say your study is special and should consider a different limit (they don't say this in their study).

That said, the only significant effect found of photo priming on high versus low fertility women was in the local attractive women group: high fertility women chose 65.8% sexy items versus low fertility's 39.1% (I could not find standard deviations for these values so have no idea how much the two groups overlap). These results are almost identical to those found when priming women with attractive women without saying if they are local or not.

How biological are we talking here?

The authors claim a biological cause for the differences found above. And maybe there is, to some extent. But there are two major issues with the authors’ conclusions.

First, there is the major methodological flaw of including women who probably aren't ovulating in their high-fertility group. Heads up to people who don't study female physiology: women, even healthy women with “normal” cycle lengths, don't ovulate every cycle. So if understanding a behavior during ovulation is important to your hypotheses, you need daily hormones on top of that LH test. Then, you know, if you can't document ovulation, you need to exclude those women from your sample. Oh, and while we're discussing methods, the authors don't mention whether the participants were in a relationship or not, or what their sexualities were, or their races or socioeconomic statuses. These are all important to understanding variation in female-female competition (Campbell 2004). And since ornamentation is likely related to honest signals of health, it would be good to know waist to hip ratios, or BMI, or facial symmetry (Streeter and McBurney 2003) (hello, I’m handing someone a dissertation here! Just remember to cite me correctly).

But the second issue relates to the theme I saw throughout this paper, that changes in mood or choice behavior due to ovulation or presence of attractive women is a "biological fact." Female-female competition is certainly found within human behavior, and behavior changes through the menstrual cycle. But is it fair to call these behaviors strictly biological, or should we have a more nuanced understanding of the interaction between biology and culture?

There are alternative cultural theories out there. Objectification theory proposes that there are consequences to living in a culture that sexually objectifies women: when women are continually appraised based on their looks, it leads to a disconnect between their body and individual (Moffitt and Szymanski 2011). This disempowers women and leads to them feeling as though their bodies exist for the pleasure of others. And if this is what women learn they have to offer others, and they seek affirmation, praise or attention from those around them, it makes sense for women to compete around attractiveness, particularly sexiness.

I would posit that shopping, particularly when primed with the image of an attractive woman, is a kind of objectification. So really, what Durante et al (2011) are measuring are the results of objectifying their study participants. Under these circumstances, a woman is more likely to start treating herself as an object to be evaluated on the basis of her appearance, so it makes sense that she would choose sexier clothing, in an effort to produce a culturally-appropriate, attractive body.

As the study stands, there is no way to parse out the impact of biology or culture -- and many cultures encourage objectification, female-female competition and female attractiveness towards men. As for how that interacts with high versus low fertility samples... that's the interesting part of this paper. If we can trust how the women are parsed. Which we can't, since some of the high-fertility sample might not have been ovulating.

These high heels are made of deer antlers

Antler booties from Camilla Skovgaard.

The authors also seemed enamored with the idea of comparing their female participants to male animals. Twice they mention the idea that they want to determine whether sexy clothing is analogous to a peacock's tail, a deer's antlers, or a lion's mane (really). These three examples, according to the authors, reflect a courtship function, a same-sex competition function, or both functions respectively. The authors go on to say that their results suggest that sexy dressing in women is like deer's antlers, or, a same-sex competition function.

First, since when are a deer's antlers only a same-sex competition function? Second, doesn't it say something that they couldn't find any examples of this kind of display in a female animal? This begs the question of why female humans do so much more displaying and maintenance of their appearance compared to other female animals, and again, this suggests interactions between biology and culture (Smuts 1995).

We can spin all the stories we want to explain why many human females make efforts to be physically attractive. And I do think Durante et al (2011) are on to something here as, despite methodological concerns they did find differences in high- and low-fertility choices. But if we continue to do this research on undergraduates in western contexts without sufficient hormone analysis, I'm unsure that its meaning extends beyond the participant pool.

References

Campbell, A. (2004). Female competition: Causes, constraints, content, and contexts Journal of Sex Research, 41 (1), 16-26 DOI: 10.1080/00224490409552210

Durante, KM, Griskevicius, V, Hill, SE, Perilloux, C, & Li, NP (2011). Ovulation, female competition, and product choice: hormonal influences on consumer behavior Journal of Consumer Research, 37 (6), 921-934

Fehring, R., Schneider, M., & Raviele, K. (2006). Variability in the Phases of the Menstrual Cycle Journal of Obstetric, Gynecologic, Neonatal Nursing, 35 (3), 376-384 DOI: 10.1111/j.1552-6909.2006.00051.x

Lenton EA, Landgren BM, Sexton L, & Harper R (1984). Normal variation in the length of the follicular phase of the menstrual cycle: effect of chronological age. British journal of obstetrics and gynaecology, 91 (7), 681-4 PMID: 6743609

Moffitt, L., & Szymanski, D. (2010). Experiencing Sexually Objectifying Environments: A Qualitative Study The Counseling Psychologist, 39 (1), 67-106 DOI: 10.1177/0011000010364551

Smuts, B. (1995). The evolutionary origins of patriarchy Human Nature, 6 (1), 1-32 DOI: 10.1007/BF02734133

Streeter, S. (2003). Waist–hip ratio and attractiveness New evidence and a critique of “a critical test” Evolution and Human Behavior, 24 (2), 88-98 DOI: 10.1016/S1090-5138(02)00121-6

Around the web: put attention where it needs to be put

Yesterday I submitted a book chapter and a journal manuscript. I have two substantial blog posts I'm working on, but neither will be ready for this week. However, I have been slowly accumulating Posts of Awesome that I'd like to share. I want to highlight people, writing, and topics that need and deserve more attention in the science blogosphere. I mention a lot of these things on Twitter, but I know a lot of my followers don't use Twitter. So here goes.

Ladybusiness

If you have any interest in pregnancy, labor and birth, I do hope you're reading Science and Sensibility. S&S is a evidence-based blog written by practitioners and scientists, sponsored by Lamaze International. I really like their more technical, informative posts on labor and birth, and today's post on positioning during the second stage of labor is a winner. The writing is always accessible for layfolks, yet still provides great information for scientists and medical folk.

Remember that Wax et al (2010) article showing homebirth had a mortality rate three times higher than a hospital birth (and the sensational Lancet editorial)? A lot of folks came down hard on the article when it first came out, myself included, but two more pieces came out yesterday that call into question the authors' conclusions. The first issue is that there were actual mathematical errors in the data (meaning, the data was probably entered into an excel sheet incorrectly), the second is that they fundamentally did the meta-analysis wrong. Wrong. As in, according to one statistician who had no stake in the story or topic, so wrong as to overlook all its other problems.

A few more spicy tidbits: cosmetic breast surgery is on the rise, and one county in Florida has a 70% cesarean rate. Seventy. Percent. Due to some smart marketing and bad decisions, a treatment to prevent pre-term birth that used to be affordable is now more expensive than gold.

Something a little more fun: older female elephants make better leaders. Here's a video to go with the paper.

Finally, this is sort of ladybusiness, but as Dr. Isis points out, it should really be family (or even just human) business: Why it's alright to not be your mother, a guest post on AGORA.

Queering biology

The reverberations from Jesse Bering's post on homophobia as an adaptation continue. And the responses have been brilliant. I especially love Jeremy Yoder's take over at his blog, Denim and Tweed: An adaptive fairytale with no happy ending.

And then today, DeLene Beeland shared this great post on Twitter: How to Queer Ecology: One Goose at a Time over at Orion Magazine. This is a beautifully-written, thoughtful takedown of the naturalistic fallacy.

Other things to read right now

Danielle Lee has two great pieces worth reading (and I found them both because of Greg Laden): an article on the contribution of Henrietta Lacks, and the Black community, to cell culture, and a profile on Danielle in a natural hair series at Essence.com.

I read this article today by Gina Trapani on her work to make the technical world more friendly to women and other underrepresented or new folks.

An interesting interview and review of the book Consumption, by Kevin Patterson: How western diets are making the world sick.

A piece on Impostor Syndrome at SciAm (behind a paywall). I don't want to pathologize all underrepresented groups in science (because frankly, these feelings make sense in the context of environment, even if it's desirable to move beyond them), but issues around impostor syndrome resonate with me.

The video for the MLK, Jr session from Science Online 2011 is now up. Alberto Roca, Danielle Lee and David Kroll are the fabulous panelists.

Things I wish I didn't have to link to

Our amusement with Charlie Sheen just demonstrates how little we care about violence against women -- especially certain kinds of women. Read The Disposable Woman.

Skepchick Rebecca Watson shares some of her hate mail, and why she doesn't feel like internetting today: Why I deserved to be called an offensive bitch.

Pat Campbell reposted a twelve-year-old manifesto on gender and education that still holds true: The Gender Wars Must Cease.

Some LOLz and some cutes: a section I added because the last three links were so depressing

This first link doesn't exactly bring the LOLz, but is an enjoyable read: Female Science Professor continues her series on Academic Novels.

Some great apes from Zooborns: a two new baby orangs, and baby chimp. They put my maternal instinct into overdrive.

And a LOLcat via Scicurious: I'z in yer papers, messin' wit yer stats.

References

Wax, J., Lucas, F., Lamont, M., Pinette, M., Cartin, A., & Blackstone, J. (2010). Maternal and newborn outcomes in planned home birth vs planned hospital births: a metaanalysis American Journal of Obstetrics and Gynecology DOI: 10.1016/j.ajog.2010.05.028

Editorial staff (2010). Home birth--proceed with caution. Lancet, 376 (9738) PMID: 20674705

USA Today piece on evolutionary psychology

For those of you who don't follow me on Twitter, just a quick note to let you know that I was interviewed for a piece on voice pitch and infidelity for USA Today by journalist Dan Vergano. It was a great experience, and a thoughtful piece.

Deep voices trigger infidelity jitters.

Mate magnet madness: When the range of possible explanations exceeds your own hypothesis

Figure 1. My apologies to Baby Jaguar
for not finding a picture that included
him.

My daughter will be three in just a few weeks. She loves telling stories. These stories have the same, uncomplicated arc every time: she and her friends Dora, Diego, Boots and Baby Jaguar go on an adventure to rescue Mommy from the giant condor. Or sometimes Mommy and Dora and Diego and Boots and Baby Jaguar are rescuing her. Or sometimes Daddy does the rescuing.

There is almost always a net, then a pair of Rescue Scissors needed to cut the captive free. But the variation in these stories is very small, the framework borrowed heavily from one of the few mythologies known to my little girl: Dora the Explorer.

Evolutionary psychology is often a kind of story-telling, and instead of borrowing from a preschool cartoon they borrow from the concept of anisogamy. Anisogamy is sexual reproduction formed by unequal gametes, in our lineage a big egg made by females and little sperm made by males. This provides the foundation for differential reproductive investment, where females often put in the time and effort of gestation, lactation and care. From here, proponents of EP see essential differences between what men and women want in relationships, and the kinds of relationships that are optimal, and a model this broad makes it possible to shoehorn any behavior into its adaptive framework.

Figure 2. The actual image that
accompanied Tierney's column.

Enter John Tierney, my (not) favorite journalist for the New York Times. This is the man who thinks that sexism is a radical act (I am referring to his charming articles on gender disparities in science). So I suppose I shouldn’t have been surprised when he outed himself as an EP fanboi in his most recent piece, “The Threatening Scent of Fertile Women.”

Tierney covered the work of Jon Maner and others who have studied relationship maintenance – the suite of behaviors that keeps a couple together. In particular, Tierney focuses on the problem of the wandering eye, or rather, the possible mechanisms that prevent it in a monogamous couple. The idea here is that relationship maintenance is evolutionarily adaptive, because when a couple stays together it is easier to raise offspring and increase reproductive success.

The range of explanations

The study that frames Tierney’s column is Miller and Maner (2010). Thirty eight undergraduate men rated the attractiveness of a woman with whom they interact, at several points over her menstrual cycle. The authors found NO relationship between where a woman is in her cycle and how attractive a single man finds her, but a negative relationship between the chance a woman is fertile and how attractive a partnered man finds her.

What do Miller and Maner (2010) discuss, and what is the idea Tierney is so enamored with?

“It’s possible that some of the men in Florida were just trying to look virtuous by downgrading the woman’s attractiveness, the way a husband will instantly dismiss any woman pointed out by his wife. (That Victoria’s Secret model? Ugh! A skeleton with silicone.) But Jon Maner, a co-author of the study, says that’s unlikely because the men filled out their answers in private and didn’t expect the ratings to be seen by anyone except the researchers.

“It seems the men were truly trying to ward off any temptation they felt toward the ovulating woman,” said Dr. Maner, who did the work with Saul Miller, a fellow psychologist at Florida State. “They were trying to convince themselves that she was undesirable. I suspect some men really came to believe what they said. Others might still have felt the undercurrent of their forbidden desire, but I bet just voicing their lack of attraction helped them suppress it.””

This conjecture is unconnected to the study’s methodology and results. Nowhere in that study did they assess the participants’ state of mind or ask them how they felt about this. How do we know they were trying to convince themselves of anything? This finding, while interesting, does not test their hypothesis for an evolutionary framework for relationship maintenance that includes adaptively suppressing attraction to others.

Maner et al (2009) studied the attention people pay to images of attractive people of the opposite sex when first exposed to sexual words like “lust” and “kiss.” They recruited 120 straight undergraduates, thirty six of whom were in committed relationships. Individuals in committed relationships paid far less attention to the attractive images than those not in relationships. Tierney titters,

“The subliminal priming with words related to sex apparently activated some unconscious protective mechanism: Tempt me not! I see nothing! I see nothing!”

I’ve done my own share of human subjects research, and subjects will often tell you or do what they think you want, or they will just not be honest if they don’t want you to know the truth. What if, as originally posed by Tierney himself, the respondents weren’t warding off temptation but wanted to look virtuous? What if, now bear with me because this might seem crazy, the people in these studies were in love with their partners and genuinely uninterested in anyone else? Too often EP wants to provide a single explanation for a behavior, when the range of possible explanations far exceeds their hypothesis.

An anthropological perspective

Jamie Jones, Associate Professor at Stanford and blogger at Monkey’s Uncle describes anthropology like this,

“…[A]nthropology is the science charged with explaining the origin and maintenance of human diversity in all its forms. To achieve this end, anthropology must be unapologetically grand in its scope. How can we explain human diversity without documenting its full extent, through both time and space, and across cultures? … Where does the tapestry of human diversity come from and how is it that we continually manage to resist powerful homogenizing forces and hang on to our diversity? What commonalities transcend local difference to unite all humanity? How is it that civilizations rise and fall? And what is the fate of humanity?”

Jamie beautifully depicts the importance of documenting and understanding diversity even in the face of efforts to simplify human nature. Thus, to me, an anthropological perspective is often at odds with EP explanations for behavior.

An anthropological perspective asks, what happens if you take these basic observations and, instead of deciding on a favorite explanation and applying it to everyone, put them into a model in which you can vary context (age/sex specific mortality rates, distribution of resources, what have you) and see what range of strategies actually give fitness benefits? That is, when you actually throw some variation into the equation, is this still the best strategy for the partnered men with whom Tierney feels simpatico?

Right now we don’t know. Much psychological empiricism rests on undergraduates who participate in studies for course credit. When one wants to make connections to evolutionary adaptedness, they may be a place to start, but not end.

I have a real problem with continuing to use this population to make statements of universality for all humans. Undergraduates usually are trying to avoid pregnancy and build their financial and social capital, so relationship maintenance for the sake of reproductive success rarely exists. Until we can show that relationship maintenance, and the particular behaviors Miller, Maner and others study within that are shown across many populations, and particularly across reproductively-aged folks, their argument for adaptation fails.

Figure 3. Celebrations of marriage.

Another problem is that most work on relationships in EP tends to be heteronormative, meaning that they think nothing of assuming that either everyone is straight, or the universally best behavioral strategy is to be straight. They also tend to assume that the best strategy is to be monogamous, with occasional sneaky infidelity permitted if one can get better genes or more offspring that way (keep in mind that there is a difference between what might be biologically advantageous in a certain context, and what is culturally appropriate – the argument here is not against the culture of monogamy).

But heterosexual monogamy is only one reproductive strategy of many that humans employ. Depending on how you measure it, monogamy and polygyny (single male, multi female marriage) vie for the most frequent strategy – in fact, polygyny occurs in about 80% of modern human societies (Murdock and White 1969). There are even a few rare populations that practice polyandry, which is the marriage of a single female and multiple males. And, even in those populations where monogamy is practiced, serial monogamy is far more frequent than lifetime monogamy: this means that individuals have a series of monogamous relationships rather than find one mate for life (so no, divorce is not a modern human invention).

When taking an even broader, comparative perspective, monogamy isn’t practiced by our closest relatives at all. Chimpanzees and bonobos, both equally related to us, are promiscuous. This is a scientific term for a reproductive strategy that involves females and males making reproductive decisions to mate with many individuals at each fertile period. Bonobos are also promiscuous, but they also use heterosexual and homosexual sex to reduce stress and aggression, and form bonds among one another. Gorillas, our next closest relative, are polygynous. Orangutans are very solitary, but essentially promiscuous. It’s only once you delve into the lesser apes, the gibbons, that you see any monogamy, and they are far less monogamous than we first thought (Brockelman et al 1998).

Maintaining a heterosexual, monogamous relationship is certainly advantageous at certain times, in certain contexts. But it is not universally adaptive, even within humans. Without anyone studying these behaviors in populations that use different reproductive strategies, and in the absence of comparative data to support these assertions, we are at an impasse.

Conclusion

In the words of a friend, EP is plugged into evolutionary theory with little more than a ratty old extension cord. EP takes some very basic, ancestral conditions, like differential costs of reproduction, and uses it in a sufficiently vague way that any behavior can relate to females generally being the ones to put in all the time and effort into making babies. Yet EP often ignores the three conditions necessary for natural selection, the mechanism for evolution. For natural selection to act on a trait, the trait must be variable, heritable, and produce differential reproductive success. Rarely does EP understand variation in a trait, rarely does it examine whether said trait has a genetic component, and rarely does it test whether their trait confers a reproductive advantage.

Are fertile women a threat to partnered harmony, their scents providing a temptation that noble men must suppress? I can’t rule it out, but I also think it is one of the least likely of many possible explanations.

Unfortunately for readers of the New York Times, Tierney loved this idea more than he loved interrogating it.

Acknowledgements

I’d like to thank Charles Roseman, friend, faculty curmudgeon and Bastard Colleague from Hell, for taking a look at an early draft of this post and providing commentary crucial to its improvement. Any rhetorical or scientific errors are my own.

References

Brockelman, W., Reichard, U., Treesucon, U., & Raemaekers, J. (1998). Dispersal, pair formation and social structure in gibbons ( Hylobates lar ) Behavioral Ecology and Sociobiology, 42 (5), 329-339 DOI: 10.1007/s002650050445

MANER, J., GAILLIOT, M., & MILLER, S. (2009). The implicit cognition of relationship maintenance: Inattention to attractive alternatives Journal of Experimental Social Psychology, 45 (1), 174-179 DOI: 10.1016/j.jesp.2008.08.002

Miller, S, & Maner, J (2010). Evolution and relationship maintenance: Fertility cues lead committed men to devalue relationship alternatives Journal of Experimental Social Psychology, 46, 1081-1084

Murdock, G., & White, D. (1969). Standard Cross-Cultural Sample Ethnology, 8 (4) DOI: 10.2307/3772907

Image sources

Dora picture: http://www.doratheexplorertvshow.com/dora/dora-explora-pics.htm
Lady magnet: http://www.nytimes.com/2011/02/22/science/22tier.html?_r=2&ref=johntierney
Same-sex marriage: http://markusisthedrug.onsugar.com/date/2009/05/07