Tuesday, March 19, 2013

Dare to be different: Defense of the research of sex differences

By Guest Contributor, Emory Neuroscience and Animal Behavior Graduate Student Katy Renfro

In a recent article published in the journal Neuroethics, Dr. Rebecca Jordan-Young and Dr. Raffaella Rumiati argue that current research on sex differences is “both unscientific and far from politically neutral,” and should be abandoned. [6] This article reflects many of the current conversations on the ethical implications of researching sex differences, which have largely focused on how results of these studies can be misappropriated to support sexist agendas. I cannot argue against the legitimacy of these concerns, and as researchers, we must always be careful to present our findings in a balanced and accurate manner so as to better combat misinterpretations and misrepresentations of data. However, we must also keep in mind that just as science has the potential to influence social and political conversations, this is a bidirectional relationship, and politics also have the power to misinform science.

In their paper, Jordan-Young and Rumiati argue that current research on
sex differences is "both unscientific and far from politically neutral." [6]

In their article, Dr. Jordan-Young and Dr. Rumiati offer two alternatives to sex difference research; the avenue they appear to more actively promote is to ignore sex differences altogether, in favor of researching differences between groups of people, such as socioeconomic or occupational classes. I believe this suggestion is an example of political motivations influencing science. Due to past and current sex/gender inequalities, there continues to be a strong push for leveling the sex/gender playing field. Although I am (of course) a strong supporter of equality between the sexes, I think it is misguided to push for the abandonment of a fruitful field of research because of the possible political implications of its results; indeed, I find the suggestion that we should halt inquiry in this area both unethical and unscientific.

Below, I provide rationale for why abandoning the study of sex differences would have ramifications for basic science research, and I then offer ways in which we as scientists can better address the potential political implications of the results of our studies.

Brain, body, and behavior

In Dr. Jordan-Young and Dr. Rumiati’s article, the researchers distinguish the body from the brain, asserting that although there are clear phenotypic differences between men and women that are due to hormonal effects, these differences are not representative of neural or behavioral differences. They support this claim by setting up a thought experiment: if a group of men and women were given images of male and female genitalia and were asked to categorize the images by sex, they would easily be able to do so; however, the same would not hold true for the brain—there are no gross, morphological indicators of the prototypical “male” and “female” human brain.

A different thought experiment: would it be possible to categorize men and
women's gastrointestinal tissues by sex?
In response, I will propose another thought experiment. If one were to gather a group of men and women, and provide them with photographs of men and women’s gastrointestinal (GI) tissues (i.e. their stomachs), would they be able to categorize them by sex? I am fairly sure the group would perform this task at no better than chance. However, if one were to use modern scientific techniques to assess the pH and enzymatic profiles of these stomachs, and examine these profiles with help from the literature, it would become immediately apparent which belonged to the men and which belonged to the women, as men and women differ in acidity of gastric secretions and in activity of a number of gastric genes. [8,5] In fact, if one were to assess activity of even just one enzyme: alcohol dehydrogenase, he/she would most likely be able to differentiate the GI tissues by sex, as this enzyme is much more active in men than women. If we take this a step further, and look for an alternate macro reflection of this difference that is not evident in the organ’s physical appearance, we could ask whether differences in this gene are related to behavioral sex differences, and the answer would be yes. When men and women drink comparable amounts of alcohol, men (due to greater enzymatic activity) have significantly lower blood alcohol content (BAC), and thus can drink markedly greater amounts before experiencing the adverse side effects of high alcohol consumption. [4, 7, 2, 3]

Because researchers looked deeper than the organ’s physical appearance and revealed these sex differences, they then had clearer directions to follow when looking for the mechanisms underlying these differences, as a sex difference indicated that prenatal and/or circulating hormones could be at play. Indeed, it has been found that altering hormone levels affects expression of alcohol dehydrogenase (e.g. [1]). There are, of course, also environmental and other biological factors that modulate these sex differences in enzymatic activity and alcohol consumption (e.g. overall body size, regularity of alcohol consumption); however, recognizing that there is a sex difference allows for more careful investigation into underlying mechanisms, as one can use this information to generate hypotheses and design experiments that specifically examine the role of hormones. To ignore the sex difference would be to ignore an integral piece of the scientific picture.

There are reported sex differences in the prevalence of nearly every major mental illness. [4]

Our internal organs cannot be completely divorced from our phenotypes; our body cannot be completely divorced from our brain, and both the brain and the body affect and are affected by our behavior. Just as recognition of sex differences provided a window into the mechanisms underlying alcohol consumption and alcohol-related disease prevalence, so it can provide us with clear avenues through which to explore the neural mechanisms of behavior. For example, there are reported sex differences in the prevalence of nearly every major mental illness [4]; ethically and scientifically, we cannot afford to deny these differences if we seek to better understand the basic biological mechanisms of illnesses such as depression, substance use disorders, and generalized anxiety disorder. Indeed, only after we understand the biological mechanisms of a disease can we better develop novel and effective treatments for it.

Conclusion and future directions

Knowledge always carries with it the potential for misuse; this is true for all scientific advancements, whether they be technological, chemical, or biological in nature. In using the example of these discoveries with the stomach, one could imagine that these results could be used to support differential regulations on alcohol consumption between the sexes, or to portray woman as “too pure” to consume alcohol “like a man.” However, it is these threats to equality that we should specifically work to eliminate—not the science of sex differences.  The discovery of “difference” does not have to mean the discovery of ammunition to fuel societal inequalities. Indeed, difference itself carries with it no moral value or attribution of goodness/badness; it is culture that assigns value to these differences. Some of the strongest resources we have to combat misrepresentations of data are social media sources. As researchers, we should take on the responsibility of writing accurate and politically neutral pieces on our research so the public is presented with a clear picture of what we did in the experiment, what was found, and what it means. Through social media avenues, such as youtube videos, blogposts, or twitter links, we can promote these pieces and reach larger audiences. It should also be our responsibility to monitor the way our results are interpreted by outside sources and to counter misrepresentations—this is a responsibility that some researchers have already taken on (for example, see Dr. Lisa Diamond’s defense of her research on sexual fluidity against the National Association for Research and Therapy of Homosexuality’s misuse). In an increasingly “flattened” world, knowledge spreads within minutes; our job as scientists should not be to stop learning or to stop the dissemination of knowledge, but rather to make sure that we are among those disseminating it, so that it can be done so in a responsible manner.

[1] Aasmoe, L, & Aarbakke, J. (1999). Sex-dependent induction of alcohol dehydrogenase activity in rats. Biochemical Pharmacology, 57(9), 1067-1072.

[2] Baraona, E, Abittan, C S, Dohmen, K, et al. (2001). Gender differences in pharmacokinetics of alcohol. Alcoholism: Clinical and Experimental Research, 25(4), 502-507.

[3] Ceylan-Isik, A.F., McBride, S.M., & Ren, J. (2010). Sex differences in alcoholism: who is at a greater risk for development of alcoholic complication? Life Sciences, 87, 133-138.

[4] Eaton, N. R., Keyes, K. M., Krueger, R. F., et al. (2012). An invariant dimensional liability model of gender differences in mental disorder prevalence: Evidence from a national sample. Journal of abnormal psychology, 121(1), 282-288.

[4] Frezza, M, di Padova, C, Pozzato, G, et al. (1990). High blood alcohol levels in women. the role of decreased gastric alcohol dehydrogenase activity and first-pass metabolism. The New England Journal of Medicine, 322(2), 95-99.

[5] Gandhi, M., Aweeka, F., Greenblatt, R.M., Blaschke, T.F. (2004). Sex differences in pharmacokinetics and pharmacodynamics. Annual Review of Pharmacology and Toxicology, 44, 499-523.

[6] Jordan-Young, R. & Rumiati, R.I. (2012). Hardwired for sexism? Approaches to sex/gender in neuroscience. Neuroethics, 5(3), 305-315.

[7] National Institute on Alcohol Abuse and Alcoholism (1997). Factors influencing alcohol absorption and
metabolism. Retrieved from: http://pubs.niaaa.nih.gov/publications/aa35.htm

[8] Whitley, H., & Lindsey, W. (2009). Sex-based differences in drug activity. American Family Physician, 80(11), 1254-1258.

Want to Cite this Post? 
Renfro, K. (2013). Dare to be different: Defense of the research of sex differences. The Neuroethics Blog. Retrieved on Monday, Day, Year, from 


Tobalee said...

I couldn't agree with you more. To make matters worse, even in studies where sexes are recruited equally, there is no attempt to stratify results based on sex, which impedes our ability to base intervention and prescribing mechanisms on real evidence (see: Wood SF. Tracking inclusion of women in clinical studies. J Womens Health (Larchmt). 2009 Mar;18(3):301-2; Dhruva SS, Redberg RF. Clinical trial enrollment and progress in women's health. JAMA. 2011 Mar 23;305(12):1197; author reply 1197-8; Chilet-Rosell E, Ruiz-Cantero MT, Horga JF. Women's health and gender-based clinical trials on etoricoxib: Methodological gender bias. J Public Health (Oxf). 2009 Sep;31(3):434-45.)

Unknown said...

Thumbs up to the author of this blog post. Thanks for defending what should be a common-sense position for all of us in science. Its not the knowledge that's harmful, its what you do with it.


Bradley Cooke

BubbaRich said...

That's a little ridiculous, that studies wouldn't even segregate medical and psychological studies by gender. I believe most of the ones I've looked at have segregated when it is meaningful to do so. (of course, further studies may be necessary to confirm when it is necessary to segregate).

I cannot believe that anyone would deny meaningful physical differences between genders in studies of the mind. It is probably gauche to mention "hormones" when discussing gender differences, but so much brain (and therefore mind) function depends heavily on hormones with gender differentiation.

I might be biased in imaging such people by the many people I usually meet around Georgia and Alabama, who either tacitly support or directly suggest keeping women in their place.

Nick Black said...

Nice post. The fact that you even have to make the point that the genders are different is absurd. It also makes me glad I do not work in academia...yet at least.

I think this post begs another question: Even if we could make the genders as similar as possible and try to negate some of the hardwiring, would we want to? Men and women are wired certain ways for specific reasons.

Also Katy, I came across this a while ago and I am really curious to hear your intelligent thoughts on the scientific argument he puts forward: http://heartiste.wordpress.com/2013/01/15/the-manjaw-ification-of-american-women-science/

Yea, probably a trigger warning on that one.

Laura E. Mariani said...

Whoa, you are posting a link to a pickup-artist website describing how folks treating their daughters as equal to their sons causes women to grow "man-jaws" in response to Katy's very even-handed blog post about physiological sex differences? I don't want to put words into Katy's mouth, but I will take a few from her post above: "It should also be our responsibility to monitor the way our results are interpreted by outside sources and to counter misrepresentations." I would describe that link as a misrepresentation of the research carried out by Amy Cudy. To put it lightly. (One of the many, many things wrong with it: we discussed using testosterone measurements to draw conclusions about behavior during previous sessions of the Neuroethics Journal Club -- it is not a perfect method, and higher testosterone doesn't always correlate with higher aggression, risk-taking, or other stereotypically "Alpha male" behaviors.)

I think Katy's critiques of the way some feminists have approached research on sex differences are totally valid -- it's foolish to say that male and female brains aren't different just because their gross anatomy is the same. But, reading blog posts like the one you linked makes it easy to see why some feminists feel the need to take hard-line positions against the use of scientific research to "prove" sex differences, especially when it comes to studies on brains and behavior (as opposed to more socially neutral processes like digestion). When a study on elevated circulating testosterone (in both men and women!) under certain conditions is used to argue that the "rancid ideology" of feminism is being used to "MAKE WOMEN MANLIER," it's enough to make me want to give up on those kinds of studies forever. Thankfully I'm not the only scientist in the world, so I'm sure someone will keep on doing them.