On the Fluidity of Gender as “Normal”– A Case Against Traditional Gender Categories in Psychology and Neuroscience Research

Psychology and neuroscience have always been concerned with anomalies. Whether this means studying a small population with a rare disease, or teasing apart seemingly trivial differences in behavior, human experience that deviates from accepted norms is rife with potential for scientific understanding and progress. This notion is relevant in psychological and neuroscientific pursuits of gendered differences in behavior and brain function. The terms gender and sex have been used interchangeably in much scientific literature. In reality, the two mean quite different things: The term sex indicates an assignment of male or female at birth, based on biological norms and expectations. The term gender, on the other hand, is distinctive from sex in that it does not necessitate congruence with sex. Gender is the identity which one feels or claims, often male or female, and exists independently from biological, assigned sex.

Historically, the gender binary has been comprised of male and female. These two categories have often been presented as exclusive and opposing. In the fields of psychology and neuroscience, much research has relied on the categories of male and female as separate and distinct. Even when sex and gender are recognized as separate, as in the case of transgender persons, for example, people are categorized as either men or women. Study participants have largely been classified as either male or female with no alternative or expanded option. This mimics the norm of the gender binary in western society today. Society allots little room for deviance from the gender binary and expectations of masculinity and femininity that accompany it. Gender nonconformity is regularly treated as an abnormality affecting a very small minority of the population. Psychology and neuroscience research that relies on the gender binary for interpretation and meaning of scientific findings would need to be reassessed if, perhaps, the gender binary is not as solid as society would like it to be.

Research conducted by Joel et al. (2013) supports the deconstruction of the gender binary based on their findings that point to a more fluid and elastic experience of gender than the male/female binary allows for. Importantly, their research challenges the myth that gender nonconformance is a rare occurrence in typical populations. Joel et al. (2013) developed a novel questionnaire that measures multiple facets of gender identity in ways which prior psychology research had not. As illustrated in Figure 1 below, there was extensive overlap in the experiences of male and female identified participants in regards to their gender and whether or not they felt “as a man” or “as a woman” (Joel et al. 2013). It is key to note that participants in normative male and female categories showed a wide spread of responses as to whether or not they felt as a man or as a woman.

These findings do indeed indicate that gender is much more fluid than the male/female binary allows. Thus, Psychology and Neuroscience need to account for that fluidity both in future research but also in reassessing the soundness of prior research that relied on the male/female dichotomy for meaning. Furthermore, it is important for research to expressly solicit information on gender identity and gender sentiment versus relying on stereotypical external cues to gather the gender of a participant based on researchers’ assumptions. This is particularly important when it comes to research on transgender persons. The research from Joel et al. (2013) also challenges the distance felt from trans* related research based on the conceptions that transgender experience is a seemingly distant “ism” and that gender nonconformity supposedly only affects a small percentage of the population. “Stable” gender categories are, in reality, not very stable. Given the findings from Joel et al. (2013), it is also interesting to consider how gendered findings from animal research in psychology and neuroscience should be interpreted. One last point – this piece is not meant to question the validity of anyone’s gender identity, rather it is meant to question the commonly accepted and propagated notions of male and female as separate and exclusive categories.

 References

Joel, D., Tarrasch, R., Berman, Z., Mukamel, M., & Ziv, E. (2013). 

Queering gender: Studying gender identity in ‘normative’ individuals. Psychology & Sexuality, 5:4, 291-321.

The Effect of Sex Differences on Brain Stimulation

A recent development in the world of neuroscience has been the rise of a technology called Brain Stimulation. Although some stimulation technologies have existed for a long time (deep brain stimulation to treat Parkinson’s), a recent wave of cheap, available stimulation technologies have provided a myriad of interesting possibilities for treatment of diseases, cognitive enhancement, and human brain research. Brain stimulation has been shown to confer all sorts of effects, from increased motor skill, better memory, stronger visual acuity, better concentration, and many others. Brain stimulation can be accomplished via many methods, including transcranial magnetic stimulation (TMS), transcranial pulsed ultrasonic stimulation (TPU), microelectrode array stimulation and deep brain stimulation. Although these technologies have many benefits (accessibility, academic validity, accuracy), transcranial direct current stimulation (tDCS) is best situated with a balance of price, accuracy, evidence, and accessibility. This has elicited an enormous amount of interest from researchers and the public alike .

tDCS is a technology that uses small amounts of voltage with low direct current to slightly raise the base level of depolarization (anodal stimulation) or hyperpolarization (cathodal stimulation) at the neuronal level of a specific area of cortex. Research seems to suggest that anodal stimulation increases activity, whereas cathode stimulation decreases activity. This could be crucial in replicating or promoting desired brain states, as many brain states rely on deactivation as well as activation. Side effects of the technology depend on the individual and range from small headaches to tingling across the scalp. Because of the mechanisms involved in a neural action potential, raising the level of depolarization, tDCS effectively lowers the threshold needed to fire a neural message. Therefore, any cortical area stimulated with tDCS will see higher rates of activation than normal. It is important to note that tDCS does not elicit activation. Rather, it amplifies the tendencies that already exist within the brain for individual neurons to fire. Other brain stimulation methods such as TMS or TPU induce activation that is not generated via natural depolarization or hyperpolarization, which makes tDCS that much more attractive. Via plasticity mechanisms such as long-term potentiation, tDCS can enhance activation patterns and strengthen neural pathways much faster than normal mechanisms. tDCS has a short-term effect on the brain, and suggest that it achieves its effects through use-dependent synaptic plasticity (Demirtas-Tatlidede, 2013). This ‘amplification’ or ‘depressing’ effect has enormous potential, especially when applied to a training context.

Questions may be raised, however, of the different effects that tDCS may have males and females. There is a large body of literature suggesting that sex differences exist in the brain; it follows that tDCS may have different effects in areas of the brain where sex plays an important role in differentiation. There is evidence to suggest that certain types of stimulation work better in women than in men, specifically in the motor cortex stimulation, a main area of tDCS research and applications. Nitsche et al. state that cathodal stimulation is more effective than anodal stimulation in women, but it is the opposite in men. Anodal stimulation, on the other hand, is more effective in stimulating the visual cortex of brain (Nitsche et al., 2008). Chaieb, Antal, & Paulus, (2008) examined the effectiveness of tDCS in different genders as well; they found that women responded extremely well to anodal stimulation, and its effects persisted at least 10 minutes after stimulation. Conversely, men experienced a dampened activation effect in the same brain area with the same stimulation.

The attached figure from Chaieb et al. shows clear differences between men and women for the persistence of tDCS effects. On the left half of the figure, cathodal stimulation produced similar effects in both the male and female groups; on the right half, a significant difference is shown from 0 minutes after stimulation to 10 minutes after stimulation.

These effects have significant implications for the future of brain stimulation; the results presented in the current studies suggest that women may be more susceptible to brain stimulation. This is most likely caused by increased plasticity in the brain, allowing for the stimulation to take on a greater effect. By maintaining a high level of plasticity and being sensitive to brain changes, women may benefit more from external training and stimulation tools such as tDCS. Men, however, may need additional therapy or stimulation to attain the same effects. Based on the presented works, considerations should be made for different gender groups when conducting experiments with tDCS, and eventual applications of the technology should be aware of its different effects on males and females alike.

References

Chaieb, L., Antal, A., & Paulus, W. (2008). Gender-specific modulation of short-term neuroplasticity in the visual cortex induced by transcranial direct current stimulation. Visual neuroscience, 25(01), 77-81.

Demirtas-Tatlidede, A., Vahabzadeh-Hagh, A. M., & Pascual-Leone, A. (2013). Can noninvasive brain stimulation enhance cognition in neuropsychiatric disorders?. Neuropharmacology, 64, 566-578.

de Tommaso, M., Invitto, S., Ricci, K., Lucchese, V., Delussi, M., Quattromini, P., ... & Cicinelli, E. (2014). Effects of anodal TDCS stimulation of left parietal cortex on visual spatial attention tasks in men and women across menstrual cycle. Neuroscience letters, 574, 21-25.

Fitz, N. S. & Reiner, P. B. (2013). The challenge of crafting policy for do-it-yourself brain stimulation. J Med Ethics. doi:10.1136/medethics-2013-101458

Keshvari, F., Pouretemad, H. R., & Ekhtiari, H. (2013). The effect of gender on dorsolateral prefrontal cortex transcranial DC stimulation-induced disruption of moral judgment. Advances in Cognitive Science, 14(456), 1-12.

Kuo, M. F., Paulus, W., & Nitsche, M. A. (2006). Sex differences in cortical neuroplasticity in humans. Neuroreport, 17(16), 1703-1707.

Lapenta, O. M., Fregni, F., Oberman, L. M., & Boggio, P. S. (2012). Bilateral temporal cortex transcranial direct current stimulation worsens male performance in a multisensory integration task. Neuroscience Letters, 527(2)

Nitsche, M. A., Cohen, L. G., Wassermann, E. M., Priori, A., Lang, N., Antal, A., ... & Pascual-Leone, A. (2008). Transcranial direct current stimulation: state of the art 2008. Brain Stimulation, 1(3), 206-223.

Understanding Depression: An Interplay of Culture and Biology

Although both sexes suffer from depression, women are more likely to suffer from depression and in fact, women are twice as likely as men to develop major depressive disorder (MDD) (Guilloux et al. 2012). This sex difference is not unique to the United States but has been observed across countries ranging from high to low gender equity and economic development (Hopcroft and Bradley 2007). Researchers have continued to search for a biological mechanism that can explain a potential predisposition for depression in women but a consensus has yet to be reached. This failure to identify such a cause might be due in part to the potential existence of multiple factors. Furthermore, one may not be able to explain depression solely from a biological perspective; evidence suggests that cultural studies of depression are also important in understanding the disorder. A sociological position on illness could therefore also prove useful.

GABA interneuron related peptides, like neuropeptide Y (NPY), and other signaling molecules in the brain are among the possible genetic factors linked to a predisposition to depression. NPY, a neurotransmitter found in the brain and autonomic nervous system is thought to play a role in anxiety and stress, blood pressure, and fat storage (Gilloux et al 2012; Zhou et al. 2008). A study by Gilloux et al. (2012) focused on a section of the amygdala, a brain structure, which is associated with the regulation of emotion. In post-mortem evaluations of subjects with major depressive disorder, all of who were female, they noted a significant downregulation for the genes that encode for these signaling molecules such as NPY. With evidence that these peptides might play a role in MDD, they then looked to mouse models of depression. In their experiments, they found a similar decreased function of NPY (Gilloux et al. 2012). Thus, lower levels of NPY and related GABA neuron peptides could lead to a greater chance of developing depression. Finally, they compared these observations with similar work previously performed in male mice. This earlier study showed a less pronounced downregulation of the genes of interest, resulting in higher levels of NPY, which might help to explain this sex difference between males and females.

However, as already noted, this biological explanation might not be sufficient in understanding this unequal distribution. Other factors, such as socioeconomic status and even cultural factors within the home, also seem to play a large role in one’s chance of developing depression. These cultural forces are likely to affect one’s stress and anxiety, which could, in turn trigger depression. One study performed by Hopcraft and Bradley surveyed males and females across 29 countries on matters such as employment, marriage status, self efficacy and religion, which can all impact one’s mental wellness. In all countries, they noted that females were significantly more depressed than males (Hopcraft and Bradley 2007). To compare between groups of females, they examined each country’s Gender-related Development Index (GDI). GDI is a measurement of gender gap in regards to health, education and command of economic resources. As the study found, those in countries with a high GDI, were less likely to be depressed than those in countries with a low GDI.

Fig 1. Probability of depression by age and sex. Men and women are grouped by high or low GDI.

As the graph shows, men in countries with a high GDI were less depressed than men in countries with a low GDI. Research has suggested that everyday life is more taxing in less developed societies due to the greater threat of war, poverty, disease and social unrest to explain this phenomena. Both groups of males, however, fell below female scores for depression. Some researchers propose that males benefit from their social standing in society, resulting in the gender gap. While females may find themselves impacted from the same issues of disease and social unrest as men, males still find that they have greater self efficacy and freedom of choice, which would improve their quality of life (Hopcraft and Bradley 2007; Rosenfield 1980).

Ultimately, it is difficult to say which plays a greater role in this sex difference in depression – cultural or biological factors. Although it is appealing to pinpoint a particular biological pathway to treat, it is likely the case that society and biology are both pertinent and so neither can be discounted when considering the issue.

References

Guilloux J, Douillard-Guilloux G, Kota R, Wang X, Gardier AM et al. (2012). Molecular evidence for BDNF- and GABA-related dysfunctions in the amygdala of female subjects with major depression. Molecular Psychiatry 17: 1130-1142

Hopcraft RL and Bradley DB. (2007). The sex difference in depression across 29 countries. Social Forces 85(4): 1483-1507.

Rosenfield S. (1980). Sex differences in depression: do women always have higher rates? Journal of  Health and Social Behavior 21(1): 33-42.

Zhou Z, Zhu G, Hariri AR, Enoch M, Scott D et al. (2008). Genetic variation in human NPY expression affects stress response and emotion. Nature 452: 997-1002.

Sex Hormones and Pain

Sex hormones appear to influence levels of perceived pain.  One gauge that psychologists use to measure pain is the cold pressor test.  During this test, subjects are asked to place their left hand into a bucket of ice water and keep it submerged.  Meanwhile, with their right hand they manipulate a dial that rates their current level of pain.  They are instructed to remove their hands when the pain becomes unbearable.  Scientists have found that pain ratings and times until removal differ in conjunction with varying hormone levels.

In normally menstruating women, hormones fluctuate monthly.  These naturally varying concentrations of estradiol and progesterone found throughout menstruation have both been found to affect perceived pain intensity.  One group of scientists have found increased reports of perceived pain using the cold pressor test during the late luteal (premenstrual) phase when compared to the early follicular (when the ovary begins to prepare to release the egg) phase of menstruation (Stening et al., 2007).  There are higher levels of progesterone released in the body during the follicular phase and higher estrogen levels during the follicular phase.  Therefore, scientists think that these disparate hormone levels are what modulate the differences in perceived pain.  Another study looked for a possible mechanism for this result.  They found more μ-opioid receptor activity in response to pain in women with higher levels of administrated estrogen (Honca et al., 2013).  These opioid receptors are thought to increase pleasurable feelings and reduce pain.  From this we may infer that estrogen can help increase levels of endogenous opioids that can help reduce certain types of pain, such as pain caused by ice water.

Graph showing the relationship between pain intensity in the cold pressor test and serum concentrations of 17β-estradiol and progesterone, as obtained from a general linear statistical model.  At low concentrations of estradiol, increasing concentrations of progesterone result in increasing VAS (pain rating) of the cold pressor test. The model shows that high concentrations of both estradiol and progesterone promote an antinociceptive effect, as illustrated by the downward slope of the plane. (Stening et al., 2007)

However, things are likely more complicated than fluctuating levels of one or two sex hormones.  In figure 1 we observe that the relationship between hormones and perceived pain change based on an interaction between the two aforementioned hormones.  Increased levels of progesterone alone correlates with increased reports of pain, but estrogen and progesterone together may lead to lower perceived levels of pain (Stening et al., 2007).  This interaction complicates things much more than the aforementioned initial results that only looked at sex hormones.  These relationships are even further complicated when you look at other factors that influence pain.  For example, it has been found that women with normal menstrual cycles in committed relationships feel pain at a higher level when they are closer to ovulation while similar women not in committed relationships do not feel pain more when they are closer to ovulation (Vigil et al., 2014).  Not to mention, there are other hormones that influence how pain is perceived.  

            Clearly, pain is a complicated phenomenon.  Many factors aside from hormone levels influence how we experience pain.  These include amount of sleep, stress levels, depression levels, genetic factors, personality types, and levels of fear. These include amount of sleep, stress levels, depression levels, genetic factors, personality types, and levels of fear.  Anyway, with this knowledge we can plan painful procedures such as surgeries at times to reduce pain as much as possible.

Honca, M., Purtuloglu, T., Honca, T., Sizlan, A., Deniz, S., Kose, A., Horasanlı, E. (2013).

Effects of the menstrual cycle on injection pain due to rocuronium. Journal of Clinical

 (5), 399-402. doi:http://dx.doi.org/10.1016/j.jclinane.2013.02.007

Stening, K., Eriksson, O., Wahren, L., Berg, G., Hammar, M., & Blomqvist, A. (2007). Pain

sensations to the cold pressor test in normally menstruating women: Comparison with

men and relation to menstrual phase and serum sex steroid levels.American Journal of

 (4), R1711-R1716.

Retrieved from http://search.proquest.com/docview/68337546?accountid=7379

Vigil, J. M., Strenth, C., Trujillo, T., & Gangestad, S. W. (2014). Fluctuating Experimental Pain

Sensitivities across the Menstrual Cycle Are Contingent on Women’s Romantic

Relationship Status. Plos ONE, 9(3), 1-9. doi:10.1371/journal.pone.0091993

Why the #%!@ do we Swear? The Neuroscience Behind Sex Differences in Expletive Language

Swear words in everyday life appear a somewhat concerning, though almost essential occurrence. As most people can attest to, these choice expletives serve a variety of functions, from expressing anger, reacting to injury, promoting aggressiveness, or simply emphasizing a point. Taboo language is a widely and passionately discussed topic, often in terms of censorship and minimizing its negative impact. However, conversations in the scientific community focus on the evolutionary and biological development of swearing, and interestingly on its positive impact. A blog post titled "The Science of Swearing" suggests that swear words can achieve a number of desirable outcomes, such as joking or storytelling, stress management, group cohesion, or as a replacement for potential physical aggression.

With this multi-faceted approach to swear words, an interesting question remains: how has swearing become associated with differences between males and females. Sex differences in swear words have been reported across cultures and over time. In general, males use more frequent and more forceful obscene language than females. A review conducted by Ginsburg et al. (2003) gives an overview of past research conducted on sex differences in vulgar language, in terms of types of usage, attributions and perceptions, and why these sex differences occur.[1] They explain that there are several theories accounting for why males may swear more than females. Evolutionarily, profanity may have originally been used during male combat as a means to shock and awe opponents. Additionally, it may contribute to destructive aggressive and sexual urges in males. Comparatively, from a socialization perspective, females may be taught to use more polite and less forceful words, thus swearing less.

Studies on neurolinguistic perspectives on swearing have also contributed to knowledge of sex differences. A study by Lancker and Cummings (1999) found that use of expletives is increased in adults with Gilles de la Tourette syndrome (GTS), a condition estimated to have a 9:1 male to female sex ratio.[2] Further studies of the physiological impact of swearing on the brain have revealed some important insights. A different blog with the same title "The Science of Swearing" describes that our brains are hard-wired to react to taboo words. The amygdala, an emotion-processing center in the brain is activated in response to reading a swear word.  A potential explanation for this might be that swearing can communicate strong emotions better than non-taboo words. A sociocultural sex difference explanation relating to this could be that males are encouraged to swear to release feelings of anger and aggression while females are taught to suppress these emotions.

In addition, a fascinating role of swearing can actually be to lessen the effects of physical pain. A study conducted by Richard Stephens and Claudia Umland[3] in 2011 asked participants to stick their hand into freezing cold water and repeat either a favorite expletive or a neutral word. Perhaps unsurprisingly for anyone who’s ever smashed their toe into a piece of furniture, swearing increased pain tolerance and heart rate compared to not swearing. This study also examined sex differences between subjects. As shown in the figure below, in comparison between swearing and not swearing, males showed slightly greater differences in pain tolerance and heart rate increase compared to females.

Taken together, these findings on sex differences in swear words present several interesting implications. Since the literature on the neurological differences between men and women in swearing is relatively sparse, speculation is far more prevalent than definitive conclusions at this time. A clear finding is that males appear to swear more than females, as evidenced by attributions and stereotypes in society. However the primary inconclusive debate concerns whether this difference is due to biological factors, sociocultural learning, or a combination of the two. One biological possibility, considering the clear relationship between swearing and aggression, and higher levels of aggression in males, is that prenatal exposure to androgens and higher levels of testosterone are the mediating factors that contribute to both increased swearing and aggression in males. As Ginsburg suggests, the cultural universality of greater male expletive language suggests some sort of biological predisposition. Of course, cultural norms and rules certainly contribute to exaggerate these differences by inflicting harsher societal penalties on females for swearing than males.

The bottom line of the science of swearing appears to be that regardless of male or female, taboo words can actually benefit the speaker (not suggesting that a child uses this argument in front of their furious parent after letting an f-bomb fly) but the study of swear words undoubtedly reveals an interesting and nuanced side of human nature.

References:

[1] Ginsburg, H. J., Ogletree, S. M., & Silakowski, T. D. 2003. Vulgar language: Review of sex differences in usage, attributions, and pathologies. North American Journal of Psychology, 5, 105-116.

[2] Lancker, D. V., & Cummings, J. L. 1999. Expletives: Neurolinguistic and neurobehavioral perspectives on swearing. Brain Research Reviews, 31, 83-104.

[3] Stephens, R. & Umland, C. 2011. Swearing as a response to pain- Effect of daily swearing frequency. The Journal of Pain, 12, 1274-1281.