Wednesday, November 30th 2011
An ultrasound of my daughter during her #occupyuterus movement
Summer 2001. I had just graduated from college with a joint degree in biological anthropology and women’s studies which, as my father pointed out, was not a degree with an obvious vocational angle. I was headed to graduate school in anthropology that fall, an experience for which I was woefully underprepared. I spent the summer loafing. It was the last summer I would ever have to just loaf around, so I was going to loaf, dammit.
But I did have one job. A dear friend was pregnant and asked me to attend her birth. I prepared like a champ: I watched A Baby Story twice a day while lounging on my boyfriend’s couch (I squeezed these in between yoga, George R. R. Martin novels, and trips to Whole Foods). I also read through some of my old textbooks, including books recommended to me by a few professors, The Woman in the Body, Birth as an American Rite of Passage and Immaculate Deception II.
One early morning in July, my friend called. “We’re on our way to the hospital. I’m in labor. It will be a while, so don’t hurry,” she said. I hurried. When I got there, conditions couldn’t have been worse: as it turns out, the nurses at the hospital were on strike, the doctor my friend hated the most was the one on call, and the epidural she got once active labor commenced slowed down her contractions. The doctor broke my friend’s water without her consent then began pressuring her and her husband to have Pitocin. Pitocin was the one intervention my friend had been adamant she wanted to avoid, but the doctor kept pulling the husband to the side telling him they were risking the baby.
The nurses were not familiar with the hospital or the doctor and so could offer little support. The husband was beside himself with worry. The doctor had the bedside manner of cardboard. I thought, This is my moment. My college degree will be useful for something!
“How about nipple stimulation?” I asked.
My friend and her husband looked at me blankly. The doctor had already left the room to attend to another patient.
“Pitocin is synthetic oxytocin. Oxytocin is produced by nipple stimulation, like when you breastfeed a baby. Maybe making your own oxytocin will bring back your contractions.”
My friend and her husband continued to stare at me.
“Well, some people do use nipple stim…” one nurse said, sounding unconvinced.
That was all the endorsement the husband needed. Eyes wild, he reached across his wife’s body… and, er, stimulated her nipples. Aggressively.
My friend’s contractions started back up again, and didn’t let up for the remainder of labor. A few hours later she gave birth to a gorgeous, big baby boy.
* * *
Ten years later, I’m in the same position. My sister has asked that I attend her birth along with her husband. Her official due date was Sunday, so we’re within the window when he will be born and are playing a waiting game. Culturally, we consider the due date as a sort of deadline; if you are still pregnant after that deadline your baby is “overdue,” and you may feel you have failed as a mother (you haven’t). You may also just be sick of being pregnant, or eager to meet your new kid. Maybe your favorite midwife or obstetrician is about to go on vacation and you won’t be able to deliver with her.
Two issues contradict the notion that inducing labor when “overdue” is a good idea. First, due dates are notoriously inaccurate, as they are calculated by date of last period instead of by ovulation or implantation. This makes sense, of course, because women rarely know their ovulation or implantation days. The first half of the cycle, or follicular phase, is even more variable than the second half (Lenton et al., 1984), meaning the assumption built into calculating a due date – that the follicular phase is fourteen days long – introduces a lot of error.
Second, if you are past your due date but your baby is happy inside of you, that means you have produced a healthy, hospitable environment for her or him. More hospitals are creating 39-week cutoffs before which doctors cannot schedule inductions; this is because birth before that point carries increased risks for the baby. Further, many researchers support the maternal crossover hypothesis, which suggests a fetal trigger for the onset of labor: once the fetus begins to starve, it sends a stress signal to the mother, which commences labor (Ellison, 2001; Wildman et al., 2011). The idea is that the mother has “crossed over” some point after which she cannot provide adequate nutrition for the growing fetus through the umbilical cord. If she or he wants to keep growing, then it makes more sense to be born and receive more energy dense food, and fat, through the nipple in the form of breastmilk.
This means a baby usually should be born when it wants to be born, rather than when you, your mother in law, your boss or *cough* your sister want him to be born.
However, the cervix of a woman who hasn’t had any children yet does take longer to ripen, and so first pregnancies can be longer than the second or third (Mittendorf et al., 1993). And so the question is whether there is anything the mother can do safely to encourage the fetus to consider starting things up, or to help the cervical ripening so that any signal the fetus is sending will be more effective. Some of the most common interventions mothers try on their own include exercise, sex, and eating spicy foods (Chaudhry et al., 2011).
I am about to share some of the literature on these and other interventions. I do not explicitly recommend any particular course of action, as I’m not a licensed midwife or obstetrician. As I learned when I had my own daughter, having book knowledge is not the same as practical knowledge.
Exercise certainly makes sense as a mechanism to induce labor: bouts of physical activity temporarily increase systemic inflammation biomarkers (Kasapis and Thompson, 2005), which are associated with labor onset. Exercise also increases energy expenditure, which might increase fetal stress and cause it to decide it can get more calories out than in.
However, the evidence doesn’t seem to support exercise inducing labor or shortening pregnancy. Many studies support a role for exercise in supporting normal-weight babies (Bell et al., 1995; Campbell and Mottola, 2001; Klebanoff et al., 1990; Leiferman and Evenson, 2003), which is a great thing: have a too-big baby and birth complications can arise, and a small baby can have health issues. Exercise may also reduce the risk of cesarean deliveries in nulliparous women (that’s women who haven’t had any prior kids) (Bungum et al., 2000). And, exercise reduces the incidence of pre-term birth (Hatch et al., 1998; Hegaard et al., 2008; Jukic et al., 2011), though work-related and potentially stressful forms of physical activity may slightly increase the risk (Misra et al., 1998). So it seems as though habitual physical activity has a very beneficial effect on mother and baby. But it doesn’t make the baby come out any faster.
Unprotected sex with a man can be fun if you’re straight or bi and it’s consensual, and its role in triggering labor has mixed support. Semen contains prostaglandins, and prostaglandins can bring on uterine contractions. Further, oxytocin is produced at orgasm, which ripens the cervix (and of course, you don’t need a consenting male partner for this one). I found one study that showed that women who were scheduled for an induction but had sex at term to avoid it had a shortened gestation length (Tan et al., 2006). The same author also found, however, that both sex and orgasm were inversely correlated with spontaneous labor (Tan et al., 2009).
Spicy foods? So far, no one has systematically looked at it, though intestinal distress may trigger contractions (Chaudhry et al., 2011). And while a few herbal preparations may increase your chances, the side effects and lack of FDA regulation dictate caution without a licensed midwife or physician overseeing the process.
But there is one more intervention worth further study. Remember when my friend’s husband semi-publicly twiddled my friend’s breasts? Nipple stimulation is effective not only at helping contractions along once labor has started, but possibly also inducing labor. One paper I read reviewed the varying recommendations by midwives for inducing labor, and their nipple stimulation protocol included massaging with oil by hand until one feels contractions, or using an electronic breast pump for fifteen minutes on, fifteen off (Knoche et al., 2008). One study demonstrated that nipple stimulation leads to greater cervical ripening than a control group (Adewole et al., 1993). So the mechanism is there, the link between nipple stimulation and cervical ripening pretty well established, and cervical ripening is one of the major first steps to labor.
That said, think of late pregnancy as an #occupyuterus movement. If current events are any indicator, no good comes of forcing peaceful protestors to leave by violent means.
References
Adewole I, Franklin O, Matiluko A. 1993. Cervical ripening and induction of labour by breast stimulation. African journal of medicine and medical sciences 22(4):81.
Bell RJ, Palma SM, Lumley JM. 1995. The Effect of Vigorous Exercise During Pregnancy on Birth‐Weight. Australian and New Zealand journal of obstetrics and gynaecology 35(1):46-51.
Bungum TJ, Peaslee DL, Jackson AW, Perez MA. 2000. Exercise during pregnancy and type of delivery in nulliparae. Journal of Obstetric, Gynecologic, & Neonatal Nursing 29(3):258-264.
Campbell MK, Mottola MF. 2001. Recreational exercise and occupational activity during pregnancy and birth weight: a case-control study. American Journal of Obstetrics and Gynecology 184(3):403-408.
Chaudhry Z, Fischer J, Schaffir J. 2011. Women’s Use of Nonprescribed Methods to Induce Labor: A Brief Report. Birth.
Ellison PT. 2001. On Fertile Ground. Cambridge, MA: Harvard University Press.
Hatch M, Levin B, Shu XO, Susser M. 1998. Maternal leisure-time exercise and timely delivery. American Journal of Public Health 88(10):1528.
Hegaard HK, Hedegaard M, Damm P, Ottesen B, Petersson K, Henriksen TB. 2008. Leisure time physical activity is associated with a reduced risk of preterm delivery. American Journal of Obstetrics and Gynecology 198(2):180. e181-180. e185.
Jukic AMZ, Evenson KR, Daniels JL, Herring AH, Wilcox AJ, Hartmann KE. 2011. A Prospective Study of the Association Between Vigorous Physical Activity During Pregnancy and Length of Gestation and Birthweight. Maternal and Child Health Journal:1-14.
Kasapis C, Thompson PD. 2005. The Effects of Physical Activity on Serum C-Reactive Protein and Inflammatory Markers: A Systematic Review. Journal of the American College of Cardiology 45(10):1563-1569.
Klebanoff M, Shiono P, Carey J. 1990. The effect of physical activity during pregnancy on preterm delivery and birth weight. American Journal of Obstetrics and Gynecology 163(5 Pt 1):1450.
Knoche A, Selzer C, Smolley K. 2008. Methods of Stimulating the Onset of Labor: An Exploration of Maternal Satisfaction. The Journal of Midwifery & Women’s Health 53(4):381-387.
Leiferman JA, Evenson KR. 2003. The effect of regular leisure physical activity on birth outcomes. Maternal and Child Health Journal 7(1):59-64.
Lenton EA, Landgren B-M, Sexton L, Harper R. 1984. Normal variation in the length of the follicular phase of the menstrual cycle: effect of chronological age. BJOG: An International Journal of Obstetrics & Gynaecology 91(7):681-684.
Misra DP, Strobino DM, Stashinko EE, Nagey DA, Nanda J. 1998. Effects of physical activity on preterm birth. American Journal of Epidemiology 147(7):628-635.
Mittendorf R, Williams MA, Berkey CS, Lieberman E, Monson RR. 1993. Predictors of human gestational length. American Journal of Obstetrics and Gynecology 168(2):480-484.
Tan P, Yow C, Omar S. 2009. Coitus and orgasm at term: effect on spontaneous labour and pregnancy outcome. Singapore medical journal 50(11):1062-1067.
Tan PC, Andi A, Azmi N, Noraihan MN. 2006. Effect of coitus at term on length of gestation, induction of labor, and mode of delivery. Obstetrics & Gynecology 108(1):134.
Wildman DE, Uddin M, Romero R, Gonzalez JM, Than NG, Murphy J, Hou ZC, Fritz J. 2011. Spontaneous Abortion and Preterm Labor and Delivery in Nonhuman Primates: Evidence from a Captive Colony of Chimpanzees (Pan troglodytes). PLoS One 6(9):e24509.
Thursday, November 17th 2011
Some of the anthropologists you would have found at the 2005 Yale strike.
I have spent a lot of time in my life being employed or educated by an organization that I find problematic in some way. At Harvard, my main gripe involved the way in which the dissolution of Radcliffe College and the women’s spaces there occurred with little engagement with undergraduates: two deans met with me and two other women who were on the board of the Radcliffe Union of Students. That’s it. In response, we created a tent Women’s Center outside of the Science Center and a list of demands of what we would want out of a real Women’s Center; years later when they finally did form a real Women’s Center they did so in the basement of Canaday, which happens to be only a hundred feet or so from our temporary structure. (I say this without taking any actual credit, as I doubt our action had much of an effect.)
At Yale, my issues centered around the condescending attitude that characterized labor relations with both graduate students and the largely African-American population surrounding the gentrified center of New Haven. I committed and was arrested for civil disobedience two times in my six years there. I also went on strike twice. The graduate students do have a union, but it is still unrecognized by Yale.
At the University of Illinois where I now work, I cancelled my 750-student class during a GEO strike, despite a phone call to my home to dissuade me from such a decision. I walked the picket lines instead, and as it happens an agreement was reached when my class would have been taught, and we celebrated on the steps of Foellinger Auditorium, where I taught my class. (Again, I doubt my own decision made a difference, but you wouldn’t have known it from the tears streaming down my face as grad students sang and danced because they got the raises and benefits they needed to support themselves and their family.)
My actions had impact for me and many other people: I radicalized many female friends in college, many more colleagues in grad school, and know I served as an example for other faculty when I decided not to cross picket lines here at Illinois. These were moving, important experiences in my development as a scholar and activist. But in each of these cases, my actions as an individual had little impact in a way the institution would understand. If anything, these actions were derided by those in power, except, and this is important, when our numbers were great. If there were thousands of us picketing, that had meaning. If 700 of us got arrested, that had meaning (this happened long enough ago that I can’t find any of the longer pieces on it online). And I will return to this later in this post.
This time, my anger is with Nature Publishing Group (NPG), who owns Scientific American. My experience at Scientific American suggests that most folks here understand social media and blogs, and are respectful, thoughtful and kind. These are people who want to make the world a better place through science and science communication. And so I do my best to forgive the fact that some improvements to our network (*cough* commenting) have been under-resourced.
But NPG is a totally different lot. We’ve seen how their blog network stalled, how archaic and ridiculous their commenting policy is. We’ve seen who they employ. To be honest, I don’t read Nature unless someone pushes something to me. Instead, I enjoy my SciAm bubble and network of bright, fun thinkers.
I can’t do that now, because Henry Gee has seen fit to publish a rather limp attempt at humor that relies on fundamental stereotypes about male and female interests, desire and behavior. You can read the intelligent commentary by countless others: Anne Jefferson, who first brought this post to my attention, Emily Willingham, Christie Wilcox, Janet Stemwedel, Dr. Isis, Alex Wild, Drugmonkey, and I am probably missing several others. The only reason this article even turned up on anyone’s radar is because Nature just published two pieces of correspondence against the piece, by Ylaine Gerardin & Tami Lieberman, and Pieter van Dokkum.
I will not add to that commentary here, because frankly they said it better than I could. Instead, I want to talk about what the right thing to do is, and how to have impact, because I am struggling with answers to this myself.
When I read Womanspace, my first reaction was nausea. I felt completely sick to my stomach because I couldn’t believe that NPG would knowingly publish overt sexism. I felt completely alienated and abandoned by a journal that is supposed to publish science, not fiction that represents offensive cultural biases. Further, I am employed, however marginally or distantly, by NPG. What does this say about me and my blog? What does it mean that NPG employs someone like me who writes on feminism and science if they also publish that? Is my blog just a joke then, or a way to improve their appearance without actually changing who they are or how they think about science and scientists?
So then my next reaction was to consider the steps I needed to take to leave SciAm, since it meant being associated with NPG. I discussed it on our backforums and asked for advice. I talked a few friends about it. Would leaving have an impact? What would have an impact?
Leaving would diminish my impact, as my readership would probably not stay quite as high were I to return to my old blog. Yet, leaving would make a statement that I am not complicit with NPG and their actions. I’m not sure I know the correct choice.
Here is what I do know: leaving would allow me to feel better about myself and save face. It would allow me to walk away from the problem, back to my safe corner of the blogosphere where all my commenters were women and they were always kind and encouraging. I desperately want to do this because I am so tired of sexism and bothered by the uptick in sexist comments since moving to SciAm. There have been a lot of public attacks on women lately and calls to discuss those attacks. I haven’t contributed anything yet, first because the attacks I’ve received have been so mild compared to the death and rape threats experienced by others, and second because writing personally takes so much out of me. Being a leader, even an imperfect one alongside many other fantastic women and men, is exhausting. And every now and then even the bringer of Ladybusiness Justice needs to nap and cuddle while her daughter watches Sesame Street.
I didn’t get that nap yesterday, but I did go to bed early. And seven hours of sleep made it easier to think than five.
Maybe I would feel better if I left, at least at first. But my impact would not be the same. For now, I am not leaving, but instead am using this space to speak up against NPG policies when necessary, an #occupynpg movement, if you will. That means that, in essence, NPG is paying me to criticize them. And I can live with that, because this isn’t going to be the first time I do it. In fact, if you spot racism, sexism, heteronormativity, homophobia, or any other oppressive behavior happening at anything associated with NPG, I would like you to tell me, dear readers, so that I may write about it. If NPG doesn’t like it, they can shut down my blog or they can stop hiring and enabling sexists.
Remember when I mentioned that institutions listen when there are enough people shouting? In grad school when I spoke I reached one person at a time, across the table in a coffee shop, at the door of their home, beside them at the lab bench. Here, I can reach thousands, maybe more, and if you have a blog you can too. Write about why you find Womanspace, or anything else about NPG oppressive, and share it with a link in the comments.* Tell me about existing posts I’ve missed. Tweet about it with the hashtag #occupynpg. And share with me what you think it will take to produce a scientific community that holds itself more accountable around issues of inclusivity and scientific rigor (and yes, this might mean you disagree with my decision, and yes, I want you to be able to express that too).
*Comments that contain links often get held for moderation, so don’t double post; just give me a little time to approve it.
Wednesday, November 16th 2011
Tenth grade, at the lockers just before homeroom. My good friend Julie and I put away our coats.
“How are you?” she asks.
“Ugh,” I say. “I have a soccer game today but” – and here my voice drops to a whisper – “I got my period this morning.”
Julie looks back at me, wide-eyed. “Oh my god, I have my period too!”
“When did you get it?”
“Three days ago!”
“Oh my god!”
Yes, that is what we really said, and you have to imagine it with a trace of Boston accent. And mind you, this is before the days of OMG.
We close our lockers and head to homeroom slowly, our backpacks heavy with textbooks. I am awed by our biology. It must be our friendship, all the time we spend together in class and after school, that has led to our menstrual cycles being so aligned.
* * *
Bottlenose dolphins and synchronized swimmers
Menstrual synchrony is one of those ideas that seems to be confirmed in our daily lives. If we are menstruating at the same time, or close to the same time as a friend, the coincidence takes on a greater meaning, a sign of our time spent together, or closeness as friends or partners. It’s a private way to celebrate our bond. Perhaps for others it serves as another indicator of the ways in which girls and women are ruled by their reproductive biology.
And there are species who do have synchronous cycles. Some cycle at about the same time of year because they are seasonal breeders, like sheep, some marsupials and even some primates. Others do use social cues like pheromones from fellow females, as in rats: the urine from one female can get the cycle of another to synchronize with her.
But the study of human menstrual synchrony has suffered from three major problems: first, whether a mechanism exists that can produce menstrual synchrony, second, methodological issues with existing papers and third, statistical artifacts in how one analyzes synchrony. A related issue is that, from an evolutionary standpoint, many struggle to find a reason women would want to have synchronous cycles, and an ancestral environment in which it could even happen.
The evolution of human menstrual cycles
These days in industrial and post-industrial populations, women can expect to have around 400 menstrual cycles in their lives, give or take a few depending on the number of pregnancies they have and degree of energetic constraint they experience from breastfeeding or exercise (Strassmann 1997). Family planning and contraceptive use increases the number of cycles as well, so we are looking at a biocultural phenomenon. With so many women cycling so often, there is a higher chance of menstrual cycles aligning, or at least appearing to align.
Contrast that with the number of cycles women have in forager populations, which is probably around 50. Forager women tend to have higher energetic constraint from the amount of physical work they need to do to acquire food. This work isn’t necessarily substantial in the sense that they are sprinting all day long, but contrast walking ten miles slowly over the course of one day while carrying food and a kid with an American sitting at a desk, and you can see how the calories burned add up.
Perhaps most important of all, forager women are usually natural fertility, which means overall they aren’t actively limiting their fertility (though again, it’s important to note that they still might try to limit number of offspring). This means that within a few years after their first period they are having their first baby, breastfeeding for many years, then maybe cycling a few times before getting pregnant again. Six to eight pregnancies with four years between each one and you’re almost to menopause! You can see how rare synchrony would be in a population where women are breastfeeding or pregnant through most of their reproductive years.
Mandrill via Wikimedia Commons
Maybe we should look to our primate relatives for evidence, then: in fact two papers have come out this year testing this hypothesis in primates! Setchell et al (2011) observed semi free-living mandrills, which is a kind of Old World monkey, a group to which the Great Apes belong. Out of ten observation-years of data, they found a single year that had significant synchrony… only to have that one year fail to be significant once they corrected for multiple testing. Multiple testing corrections are important because of the chance that if you test a hypothesis enough times you will get a spurious significant result (and for a brilliant take on this, see this xkcd comic).
The other equally interesting paper to come out this year on this topic is by Fürtbauer et al (2011), entitled “You Mate, I Mate: Macaque Females Synchronize Sex Not Cycles.” Their study population was wild Assamese macaques, also Old World monkeys. Fürtbauer et al (2011) observed behavioral receptivity and measured fecal ovarian hormones (yes, that means they measured hormones in poop) in order to assess behavioral and hormonal synchrony. They found long periods of behavioral receptivity that synchronized well across individuals, but that actual estrus cycles were randomly distributed within the receptive period. I thought this paper did a great job at providing an evolutionary framework for why mating might evolve to be synchronized, but not cycles, and because the paper was published in PLoS ONE, you can read it yourself for free.
This paper resolves a question I’ve had for a long time about menstrual synchrony, which is how in the world it could actually be beneficial to females, particularly those with covert ovulation. Why would you want all the females, or even a subset of them, to be fecund and receptive at the same time? And the answer is, you probably wouldn’t. Humans, other primates, even some cetaceans like dolphins have mating that is largely decoupled from reproductive cycling. That is, we don’t only mate at the time in our cycle when our chances are highest to conceive, though we might find ourselves slightly more proceptive or receptive at that time. Sex is not just about making babies, but is an affiliative behavior, promoting bonding but also plain old enjoyment. Instead, it may in some circumstances make sense to have extended periods of synchronous receptivity, as within a promiscuous species like the Assamese macaques (Fürtbauer et al. 2011). But this isn’t necessarily an adaptive feature of the entire primate lineage.
You sniff, I sniff
The other issue that has plagued the study of menstrual synchrony is that we don’t have a good idea for how it could actually work. For most, the entire claim for synchrony rests on the presence and ability to detect pheromones. When I first heard of the idea of menstrual synchrony I read Beverly Strassmann’s “Menstrual synchrony pheromones: cause for doubt” and was sufficiently convinced to stop paying attention to the issue for many years (Strassmann 1999). Since then, I have been told by those more knowledgeable than I that humans don’t have a functional vomeronasal organ (VNO), which is necessary for detecting pheromones. Yet, people keep studying menstrual synchrony, and they even study other behavioral phenomena that would require some kind of pheromone or odor detection ability in humans, like mating preferences around immune complementarity. And some of these studies get significant results.
So, I read up on it. Turns out that while we don’t have as many scent glands as New World monkeys, humans have pretty big ones compared to other Old World monkeys. And we may not need a VNO to detect pheromones. Hays has a thoughtful, well-written review that outlines the several types of pheromones as well as the signaling pathways that could lead to human detection of pheromones, and only one of them is through stimulants to the VNO (Hays 2003). Further, certain odors are associated with some pheromones (which are themselves odorless) and genetic profiles, so the mechanism for pheromone detection could be related to the sense of smell.
That said, the mechanism for detection of pheromones related to menstrual synchrony is a weak one, not really supported by evidence. So far the only proposed mechanism does require stimulants to the VNO or pheromones in axillary sweat, and no studies have convincingly demonstrated that women respond to other women’s pheromones in this way (Hays 2003).
Fight, fight!
The last two issues around menstrual synchrony are related to methodology and statistics. And this is where the story starts to get fun.
I found a series of articles and letters in the Journal of Comparative Psychology between Schank, Weller and Weller, and Graham in the early 2000s. Schank is someone who contends there is no support for menstrual synchrony, where Weller and Weller and Graham study it and support it. The subtext of each piece was that those on the other side are flaming idiots: Schank makes parenthetical comments that question Weller and Weller’s motives, where Weller, Weller and Graham imply Schank is intentionally obtuse. It’s rollicking good fun!
Schank 2001 Table 1
Schank’s main criticisms are that many researchers who study synchrony are examining a synchrony score (where the closer the cycles are the smaller the score). A low synchrony score, then, is not actual synchrony. Further, Schank points out that synchrony scores increase over time in every paper he reviews, meaning that women become less synchronous over time in all existing study populations.
In both of Schank’s papers and his letter (Schank 2000; Schank 2001; Schank 2002), as well as Strassmann’s piece (1999) and others by Wilson (Wilson 1992; Wilson et al. 1991), the authors point out additional methodological statistical biases. Those who perform menstrual synchrony research fail to control for recall biases or random synchrony, and they inflate the initial difference in cycle onset, which creates a stronger appearance of later synchronization. Further, Strassmann points out that those who do control for these issues find no evidence for synchrony (Strassmann 1999). Finally, most critiques of synchrony research also point out that synchrony is pretty hard to come by when natural menstrual cycles are highly variable – which they are.
Weller and Weller and Graham each address these issues. Graham claims Schank is overstating the problem – in fact, she claims his statements are “inappropriate and misleading” – because his particular gripe about recall bias isn’t in the literature (Graham 2002). That is, Schank claims most synchrony studies are based on recall data, which means researchers ask women about when their last periods are, where Graham claims most of these studies are prospective, which means they do longitudinal assessments that actually ask women over time when their periods are. The answer appears to be somewhere in between, where even largely prospective studies rely on one, sometimes two previous menstrual cycle dates to create their synchrony scores.
The other Graham-Schank beef appears to center around Schank finding fault with the use of menstrual cycle calendars, where Graham contends they have been validated and used in many areas of research. Again, this is a place where the answer is somewhere in the middle. Menstrual cycle calendars are surely imperfect, but likely not enough so to warrant the heavy criticism Schank lodges at them.
Instead, frankly, I find the absolute lack of synchrony evidence in non-human primates as well as in well-controlled human studies pretty darn compelling.
Personal intuition
What about all that great anecdata, like what I describe in my opening story? Strassmann is the one who actually states the issue most accessibly:
“Popular belief in menstrual synchrony stems from a misperception about how far apart menstrual onsets should be for two women whose onsets are independent. Given a cycle length of 28 days (not the rule – but an example), the maximum that two women can be out of phase is 14 days. On average, the onsets will be 7 days apart. Fully half the time they should be even closer (Wilson 1992, Strassmann 1997). Given that menstruation often lasts 5 days, it is not surprising that friends commonly experience overlapping menses, which is taken as personal confirmation of menstrual synchrony” (Strassmann 1999: 579).
Um, yeah. So. The fact that menses overlapped between Julie and I? Maybe that would lead to a low synchrony score, for that one cycle. But it is far more likely that this overlap – not synchrony, just overlap – was a result of random chance. This doesn’t reduce the bond I had with my dear high school friend. It just means there wasn’t any substance in her sweat telling me when to ovulate.
References
Fürtbauer I, Mundry R, Heistermann M, Schülke O, and Ostner J. 2011. You Mate, I Mate: Macaque Females Synchronize Sex not Cycles. PLoS One 6(10):e26144.
Graham CA. 2002. Methods for obtaining menstrual-cycle data in menstrual-synchrony studies: Commentary on Schank (2001).
Hays WST. 2003. Human pheromones: have they been demonstrated? Behavioral ecology and sociobiology 54(2):89-97.
Schank J. 2000. Menstrual-cycle variability and measurement: further cause for doubt. Psychoneuroendocrinology 25(8):837-847.
Schank JC. 2001. Menstrual-cycle synchrony: Problems and new directions for research. Journal of comparative psychology 115(1):3.
Schank JC. 2002. A multitude of errors in menstrual-synchrony research: Replies to Weller and Weller (2002) and Graham (2002).
Setchell JM, Kendal J, and Tyniec P. 2011. Do non-human primates synchronise their menstrual cycles? A test in mandrills. Psychoneuroendocrinology 36(1):51-59.
Strassmann BI. 1997. The biology of menstruation in Homo sapiens: Total lifetime menses, fecundity, and nonsynchrony in a natural-fertility population. Current Anthropology 38(1):123-129.
Strassmann BI. 1999. Menstrual synchrony pheromones: cause for doubt. Human Reproduction 14(3):579-580.
Wilson HC. 1992. A critical review of menstrual synchrony research. Psychoneuroendocrinology 17(6):565-591.
Wilson HC, Kiefhaber SH, and Gravel V. 1991. Two studies of menstrual synchrony: negative results. Psychoneuroendocrinology 16(4):353-359.
