Part One
Theorizing Cycles and Stains
1
Cycling Together
Menstrual Synchrony as a Projection of Gendered Solidarity
In 1971, a time when the U.S. womenâs movement had catalyzed women to see themselves as aligned and in political solidarity with other women, Martha McClintock published a study on menstrual synchrony among college women living in a shared dormitory. McClintockâs studyâthe first of its kind and one that would go on to inspire decades of additional research in this areaâof 135 women ages seventeen to twenty-two living together yielded statistically significant levels of menstrual synchrony among pairs of friends and groups of female friends. The results of her study, quickly picked up by the media, spread rapidly throughout the scientific and lay communities, appearing as a fact presented on television (Rosewarne 2012) and a hotly disputed occurrence within the scientific literature (McClintock 1971, 1998; Schank 2000, 2001; Strassmann 1999; Weller and Weller 1992, 1993a, 1993b, 1995a, 1995b, 1998; Weller, Weller, and Avinir 1995; Weller, Weller, and Roizman 1999).
Here, we are less interested in the scientific debates about the existence of menstrual synchronyâthough the literature itself is a fascinating example of the controversies of science followed by an ultimate lack of conclusivenessâand more interested in the personal, social, and political implications of why many women believe they have menstrual synchrony with other women. In line with the feminist call to fuse the personal and political, the theoretical positions presented in this chapter are derived from our work as menstrual activists. As we have challenged and sought to combat the shame-based, sexist, and menstrual-negative culture around us, we have had ample opportunities to engage in conversations with women about menstruation, which has provided us a unique lens through which to view the political meanings of menstrual synchrony. Through casual conversations about menstruation on airplanes; dialogue with family, friends, students, and coworkers; workshops about alternative menstrual products; and discussions about menstrual cycles during psychotherapy, we have been continually curious about the frequency with which we have heard the statement: I menstruate together with my sister/friends/mother/coworkers/lover.
Struck by the consistency, passion, and certainty that women have when describing menstrual synchrony, particularly given that those on hormonal contraceptives do not actually menstruate, we see the overwhelming presence of the belief in menstrual synchrony as a projection of gendered solidarity with other women. Specifically, we posit at least four different possible functions of menstrual synchrony: a way to reduce shame and taboo related to menstruation; a socially acceptable way of constructing modern âsisterhoodâ; a method for marking womenâs relationship to nature; and a pathway to fight back against sexism and sexist assumptions about menstruation and menstruating women. All of these functions underlie the importance of seeing solidarity not only on purely political terms but also as a bodily, gendered, and largely personal phenomenon that has the potential to create, validate, and perpetuate social bonds between women.
Debates about Menstrual Synchrony
The menstrual synchrony literature is an unusual, controversial, and passionate literature filled with rebuttals, conflicted opinions, backtracking, accusations of methodological error, and passionate defensiveness. When we reviewed the literature on menstrual synchrony, we were reminded of Elizabeth Lloydâs (2006) brilliant work in which she examined the biases of science and the ways that scientists projected their beliefs about gender and sexuality onto their evolutionary studies of orgasm. In essence, Lloyd found that, despite having no conclusive evolutionary purpose whatsoever, many scientists nevertheless reported as fact that the female orgasm has a reproductive purpose. Even in the face of contradictory evidence, researchers, blinded by their own attitudes toward and beliefs about women and sex, proceeded to argue âfactsâ that ultimately had no scientific basis. How researchers seeâand what they seeâleans heavily on their desires for what they want to see, even (or especially) within the supposedly neutral and bias-free scientific community.
The literature on menstrual synchrony has many unusual qualities, as its origin date, size, lack of conclusiveness, and large volume of repeated follow-up studies suggest that the idea of menstrual synchrony tapped into something much larger than the mere possibility of menstrual cycle alignment. The number of studies that followed McClintockâs (1971) pioneering work helped to describe how women living together might menstruate together. McClintock, a psychologist at the University of Chicago who has studied human pheromones, menstrual synchrony, and the behavioral control of endocrinology, brought a distinctly feminist lens to the study of womenâs health and menstrual synchrony. Her most vocal critics (and those who have wavered back and forth about the existence of menstrual synchrony) have included J. C. Schank, a male psychologist who focuses on animal behavior and biopsychology; Leonard Weller, a sociologist who has studied social class and anti-Semitism (with a clear interest in social relationships between people); and Aron Weller, a psychologist interested in neuropsychology and animal behavior. Collectively, these four researchers have spent much of their careers debating the existence of menstrual synchrony and attempting to have the âfinal wordâ on the matter; it is important to note that some of them are primarily interested in animal behavior and not in health-related matters.
Theoretical Debates
Following McClintockâs (1971) landmark study, other researchers examined a variety of contexts where women cohabitated or existed in close proximity, including lesbian couples (Trevathan, Burleson, and Gregory 1993; Weller and Weller 1992), friends and roommates (Graham and McGrew 1980; Jarett 1984; Weller and Weller 1993a; Weller, Weller, and Avinir 1995; Wilson, Kiefhaber, and Gravel 1991), sisters and mothers/daughters (Weller, Weller, and Roizman 1999), coworkers (Matteo 1987; Weller and Weller 1995b; Weller et al. 1999), athletes (Weller and Weller 1995a), and women not using any birth control (Collett, Wertenberger, and Fiske 1955; Strassmann 1997). Some studies found synchrony between roommates and friends but not mothers (Weller and Weller 1993b) and that closer friendships developed more menstrual synchrony (Weller and Weller 1995b), whereas others found a large variety of factors related to menstrual synchrony, including social factors, quality of the relationships, group size, age and age diversity, menstrual regularity, the environment, and contraceptive practices (Little et al. 1989; Weller and Weller 1995c; Weller and Weller 1997). However, researchers have not assessed menstrual synchrony in groups of women who all use hormonal birth control, and some rightly note that this sort of withdrawal bleeding is different from menstruation altogether (for two studies that excluded women on birth control, see Preti et al. 1986; Russell, Switz, and Thompson 1980).
Pheromone studies have formed the basis of much of the research on menstrual synchrony to date. Although friendship, common activities, cohabitating, and the amount of time spent together all correlated with higher reports of menstrual synchrony, the researchers believed that exposure to other womenâs ovarian-based pheromones (i.e., odorless compounds emitted from womenâs bodies, especially their underarms) was largely responsible for why women cycled together (Goldman and Schneider 1987; Weller and Weller 1993a). The release of these pheromones was assumed to accelerate or delay the surge of luteinizing hormone responsible for menstrual cycle length, which resulted in women becoming increasingly more synchronized with each other (Stern and McClintock 1998).
Though many studies consistently demonstrated the existence of menstrual synchrony (particularly those by Weller and Weller), one study showed that it occurred only because of environmental influences (Little et al. 1989), and results of a number of studies led researchers to question its existence or refute its existence entirely (Jarrett 1984; Schank 2002; Strassmann 1999; Trevathan, Burleson, and Gregory 1993; Weller and Weller 1998; Weller, Weller, and Avinir 1995; Wilson, Kiefhaber, and Gravel 1991; Yang and Schank 2006; Ziomkiewicz 2006). Wilson (1992) showed that, mathematically, menstrual synchrony would be expected in half of the women studied without any external manipulation or contextual factors influencing it, as some women cycle regularly and some irregularly. He also found three methodological errors that could have skewed the results of earlier studies: too short an observational period, incorrect methods of calculating the menstrual onset differences, and exclusion of certain women from the analysis.
Evolutionary biologists have also debated the existence of menstrual synchrony, as strong disagreements appear in the literature as to whether (and why) menstrual synchrony occurs (McClintock 1998). Evolutionary scientists have theorized a variety of reasons for menstrual synchrony, including the higher likelihood for conception in societies where many women share one man (he would sense the pheromones, want to have sex with multiple women, and impregnation would become more likely, whereas unsynchronized cycles would âconfuseâ men) (Burley 1979). Menstrual synchrony has also been proposed to increase a manâs interest in his female offspring (Knowlton 1979; Turke 1984) or provide a backup wet nurse in times of high maternal mortality (Frisch 1984).
Despite these evolutionary explanations, no studies have shown that women ovulate together or have similar fertility periods while cohabitating, which refutes the likelihood of most of the evolutionary explanations (Kiltie 1982; Strassmann 1999; Yang and Schank 2006; Ziomkiewicz 2006). Even more important, urbanized and nonurbanized societies show markedly different patterns of fertility and menstruation, as women in urbanized societies have more menstrual cycles, fewer pregnancies (and longer periods of nursing), and more years when they menstruate than do women in nonurbanized societies (Strassmann 1997; Strassmann 1999; Umeora and Egwuatu 2008). Some recent evolutionary researchers have cautioned that scientists know very little about menstrual synchrony and its possible reasons, and, consequently, researchers should not draw sweeping conclusions about such a complex phenomenon (Harris and Vitzthum 2013).
Methodological Debates
Several researchers have found additional methodological problems, particularly the difficulty of assessing menstrual synchrony in light of âwithinâ and âbetweenâ women differences. Each individual woman may not have a consistent cycle length (e.g., Woman A has a 28-day cycle in one month and a 31-day cycle in another), just as women often differ between one another in their average cycle lengths (Woman A typically has 28-day cycles, and Woman B typically has 31-day cycles) (Schank 2000). Finally, some researchers found no evidence of menstrual synchrony among those not using hormonal contraceptives (Strassmann 1997; Strassmann 1999), and a few studies yielded no evidence of menstrual synchrony in lesbian couples (Trevathan, Burleson, and Gregory 1993; Weller and Weller 1998), which called into doubt the existence of menstrual synchrony in its entirety.
Furthermore, the methodological problems of studying menstrual synchronyâparticularly Weller and Wellerâs methodsâmay have created the phenomenon as an artifact of how it was studied (Schank 2000). In his review of all studies of menstrual synchrony, Schank (2001) concluded that allowing women to fill out their own menstrual onset calendars may have encouraged women to want to report synchrony rather than their actual onset dates. Weller and Weller wrote two rebuttal pieces, in which they asserted that they had used sound methods (Weller and Weller 2002a, 2002b), and Schank (2002) replied that Weller and Weller over-relied upon recall data. In short, women who wanted to have menstrual synchrony may have remembered and reported menstrual synchrony. He then went on to show that no evidence of menstrual synchrony existed (Yang and Schank 2006) and that all eight of the pheromone studies had âserious problemsâ with methodological errors (Schank 2006).
Subjective Feelings about Menstrual Synchrony
Debates among biological researchers have dominated the menstrual synchrony literature, but a few social scientists have measured womenâs subjective feelings about their personal experiences of menstrual synchrony. One qualitative study of thirteen white highly educated women, ages twenty-five to forty-six, showed that all of the women reported having experienced menstrual synchrony, and most thought that there were biological rather than social reasons for its occurrence (e.g., about hormones or chemicals) (Klebanoff and Keyser 1996). Another study (Arden, Dye, and Walker 1999) showed that women overwhelmingly knew about menstrual synchrony and believed that they had experienced it. In this study of 122 British women, 84 percent were aware of menstrual synchrony (note that the authors did not present menstrual synchrony as a controversy), and 70 percent reported personal experiences with it (Arden, Dye, and Walker 1999). Further, the women reported having experienced synchrony with close friends, roommates, mothers, and sisters, and 51 percent of them reported three or more episodes of synchrony with different women. The women in this study felt positively about menstrual synchrony (e.g., supportive, closeness, mysticism), and they said they knew about the timing of other womenâs menstrual cycles primarily through verbal communication and complaints about PMS symptoms.
The Media Storm about Menstruating Together
This critique that women may want to report menstrual synchrony and that their desire to experience it potentially biased the findings in Weller and Wellerâs work seems highly plausible given the volume of interest in and unequivocal belief in menstrual synchrony displayed in popular culture. Most film and television sources have not portrayed menstrual synchrony as a controversy. From womenâs magazines to television shows to blogs (Clancy 2011; Rosewarne 2012), women hear (and likely internalize) the notion that women who live together bleed together. As Rosewarne (2012) wrote in her analysis of the presentation of menstrual synchrony on television: âThe menstrual synchrony narrative is perhaps the strongest example of on-screen menstrual bonding, presenting women not merely united by menstruation, but by the experience of bleeding simultaneouslyâ (20).
Television shows and films have sometimes depicted menstrual synchrony both as a bond between women and as a source of horror. The series Charmed (1998â2006) depicted three witches with aligned periods: Phoebe (Alyssa Milano) was more âemotional,â Paige (Rose McGowan) was more âjumpy,â and Piper (Holly Marie Combs) was more âpissy.â In an episode of 30 Rock, Jack (Alec Baldwin) remarked offhandedly, âOh sure, we can sit around and braid each otherâs hair until we get our periods at the same time.â Howard (Simon Helberg) in The Big Bang Theory joked after watching Sex and the City: âFine, letâs watch it. Maybe all our periods will synchronize.â And, on The Office (2005â2013), Dwight (Rainn Wilson) sarcastically advised against women meeting together on their own: âIf they stay in there too long, theyâre gonna get on the same cycle. Wreak havoc on our plumbing.â An example of the âhorrorsâ of menstrual synchrony is found in the Korean film A Tale of Two Sisters (2013), which displayed two sisters who awoke to realize they were menstruating togetherâsomething the film portrays as weird and otherworldly (Rosewarne 2012).
Womenâs magazines and blogs also offer a host of (mis)information about menstrual synchrony, such as that menstrual synchrony is based on exposure to natural light (MacLeod 2013) and that menstrual cycleârelated pheromones determine the likelihood of conception (Edmonds 2010). Magazines such as Womenâs Health, Shape, Womenâs Day, New Scientist, and Bust have all discussed menstrual synchrony as well, sometimes presenting it as a compelling controversy but most often describing it as a real phenomenon. Shape writers leaned heavily on the argument that women have menstrual synchrony: âAnd itâs hard to say how factors like stress, sexual partners, and birth control play into the syncing gameâif synchrony does exist, itâs possible these factors override it, making matched cycles appear less common than they might actually beâ (Newcomer 2012). Dozens of blogsâfeminist, scientific, health, and personalâhave discussed menstrual synchrony, usually portraying it as a common and everyday occurrence.
Menstrual Solidarity
Given this evidence, particularly that scientific research has never conclusively determined that menstrual synchrony actually exists and that the media nevertheless has taken it up largely as factual, we consider the concept of âmenstrual solidarityâ to be a key motivator for maintaining the story of menstrual synchrony. We now propose our theories about why women believe in menstrual synchrony.
The concept of feminist or gendered solidarity has most often been used as a political and moral concept, that is, fighting for members of oneâs own groups and communities in the public sphere (Mohanty 2003), such as social movements against war, collective bargaining, pr...