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  • Writer's pictureAmos Gdalyahu

From sexual fluidity in women to orgasm in rape

Updated: Jul 14, 2023

We'll begin our journey in this post with the question: Do women who say they are exclusively attracted to men have in fact attraction towards women? And do those who are certain about their attraction to only women actually exhibit attraction towards men? In other words, are women generally more fluid in their sexual orientation than men? Fluidity here means a sexual orientation that is not rigid.

This question comes from a study by Dr. Meredith Chivers, a clinical psychologist and sexologist from Canada, that was published in 2013 and reinforced previous studies with similar results (1):

In the study, there were 3 groups: women, men, and transgender individuals (born as men and underwent gender transition to become women).

In all groups, in terms of sexual preference, there were those who preferred men and those who preferred women. That is, a total of 6 groups. All groups were shown pornographic films of three types: male-male, female-female, and female-male. The films included both penetration and oral sex. As a control, landscape films were used. While watching the films, the researchers measured physiological sexual arousal (for men, they used a device that measures penis circumference as a measure of erection, for women and transgender individuals, they measured vaginal blood flow. That was because increased blood flow leads to lubrication (wetness), which is essentially the release of water from the blood vessels. Therefore, measuring blood flow indicated how much wetness there was. In another study, wetness was measured directly). In addition to these physiological measurement, all 6 groups were simply asked how aroused they were by the films.

What did they find?

They found that for men and transgender individuals, there was a match between what they said aroused them and their physiology: Men and transgender individuals who identified as attracted to men showed significant genital arousal when viewing male-male sex, but not female-female sex in accordance with what they said. Those who identified as attracted to women showed significant genital arousal when viewing female-female sex, but not male-male sex as expected. And now comes the surprising part: Women didn't have such a match: Women who said they were attracted to men, although they said that movies between a man and a woman were the most arousing to them, their vagina was actually sexually aroused from all genres and at the same level. Likewise, among women who preferred women, the vagina reacted positively to movies with men to the same extent as to the movies with women! Although they said that these movies do not arouse them (1). So to summarize: Women experience sexual arousal from stimuli of any gender. This does not happen with men or transgender (male to female) individuals. Therefore, the first conclusion is that women are more fluid in their sexual response than men, and those who transitioned to women.

In addition, there is a mismatch between the physiological arousal in the vagina, which is fluid (meaning not specific to a certain gender), and what women say: that they have a sexual preference for a certain gender. That is, women do not know - or do not say - that they are fluid in their sexual response when asked what arouses them. The vaginal response to all genders has been found in many studies, even among women who suffer from lack of sexual desire or those with pain during intercourse. In all cases, even if they suffer from lack of sexual desire, there was still arousal in the vagina, the lubrication was not different from other women, and the sexual arousal was not specific to what they say arouses them, if at all. Professor Kelly Suschinsky, a psychology professor, received the same results and even added to them: she gave women a story about a violent sexual assault from the perspective of the victim (2). As expected, the women said that the story did not sexually arouse them and was even unpleasant and anxiety-provoking. However, their vaginal response was still aroused! Not only that, but it was even similar to the response they had when they heard a story about consensual sexual relations!

If before, the sexual arousal in response to genres that women said did not arouse them was taken as evidence that they were in fact attracted to these genres - and just didn't say it or didn't know they had such attraction - then the conclusion now would be that they want to be raped?! It chills me just to write that!

So of course not. It is a physical response that is not related to desire or subconsciousness . In the rest of the post, I will explain how there can be sexual arousal even during rape. I will start with Professor Suschinsky's explanation and then provide the biological explanation. I will conclude with the important implications for rape victims to know and for legal implications.

Image: cookie_studio Freepik

Instead of sexual fluidity, Professor Sushinsky suggested that the response in the vagina does not indicate any sexual desire at all, but rather a defensive response to any sexual situation (2). The reason is that in the case of rape, if the vagina is wet, there is less injury.

Therefore, any hint of a sexual situation causes a woman to become moist within seconds in an automatic and involuntary response that is not at all related to her desire for sex. Here there is only one assumption (a defense mechanism) compared to the two assumptions in the previous model (women are both sexually-fluid and unaware of it). The rule in science is to always prefer the simplest explanation. According to Prof. Sushinsky wetness meant to prevent injury. Does it really help?

In medical examination, even after consensual sex, minor injuries are found in about half of women's vaginas, especially in the lower part of it. More injuries are found in older women who have less wetness and even more after a sexual assault. This shows that the mechanism helps, but it is not perfect, and injuries still occur. In my opinion, despite its imperfection, it supports the explanation of wetness as a mechanism for protection. Prof. Sosinski's explanation is appealing to me, but it is not a proof and researchers are still trying to understand the source of the difference in sexual response between men and women.

Evolutionary explanations answer the "why" question and try to find reasoning, while the biological explanation answers the question of 'how does it happen that there are physical arousal without consent'.

For those interested in biological explanations like myself, there is an even deeper question: vaginal lubrication is supposed to occur in relaxed situations, just like penile erection in men. How is it, that in an extreme emergency situation like rape, there is lubrication for women and an erection for men? (If the question is not clear at the moment, I hope it will be clearer later on).

In order to explain the biology of sexual arousal in both men and women, I need to provide some background on the autonomic system. First, I will provide the known popular explanation, and then a more in-depth explanation. Then, I will use this background to continue my discussion on sexual arousal and answer the above question. I will conclude with implications. The 'popular' explanation of how the autonomic system works: As I explained in the previous post (here), the brain sends commands to the body in two forms: The first, voluntary (called somatic) acts for example, when I decide to lift my hand. The second, involuntary (with the autonomic and hormonal systems), acts for example, when the pupil contracts, or when the blood vessels dilate, or when I smell tasty food and my saliva starts to flow. The autonomic system (involuntary) transmits commands from the brain to involuntary muscles, glands, and internal organs. It does so with two arms: the sympathetic arm and the parasympathetic arm. The sympathetic arm works in states of excitement, and the parasympathetic arm works the opposite. At first glance, the body has one switch for the state of excitement that the sympathetic system switches to the ON state, while the parasympathetic system switches it to the OFF state.

There is some truth in this explanation, but the reality is more complex, and it is critical to understand it to comprehend the rest. The deeper explanation:

The action of the sympathetic system on the body occurs in two ways:

1. An activation of the adrenal gland. When the adrenal gland is activated, it releases adrenaline into the bloodstream. Adrenaline is actually a general switch, as people think of the autonomic system. It prepares the body for an excited state, for a Fight or Flight state. Adrenaline accelerates the heart rate, expands the airways, dilates the pupils, diverts blood from the digestive system to the muscles, shifts the liver to produce and release glucose into the blood, and more. This response takes at least a few seconds (adrenaline reaches the target organs through the blood) and lasts at least a few minutes.

2. The second and less popularly known mode of action of the sympathetic system occurs through a direct, specific and rapid neural innervation of target organs. Each target organ has its neural switch. Indeed, in different states of arousal, different bodily reactions are elicited. As shown in the graph below (3), fear activates the body differently than anger, and both activate the body differently than disgust.

Before I continue to the parasympathetic system, I will add two interesting and important side notes:

  1. The possibility of selective activation of different sympathetic switches in different situations creates a repertoire of different bodily responses (3). The different bodily responses may allow the brain to close the loop it started: through self-observation of the bodily response (introspection), the brain can understand what emotion triggered the autonomic system. This is in addition to the information that the brain itself has about the situation. In a future post I'll expand on theories of emotions. A story to illustrate this idea of introspection: a neuroscience student who knew everything I just wrote here wanted to start a relationship with a girl at his lab. He invited her to a roller coaster ride assuming that the excitement and arousal she would feel in her body would be interpreted by her as falling in love with him when her brain closes the loop. When they got off the ride, gasping for air, he said "wow that was amazing! How was it for you?" and she replied "for me too! And how handsome was the guy sitting next to us!"...

  2. Usually, there is a correspondence between the bodily response and the conscious image, but not always, for example in traumatic situations there is no. In a traumatic state of dissociation, there is a sub-activity of the sympathetic system that does not match the conscious perception of extreme fear, while in post-traumatic stress disorder there is a constant excessive activity of the sympathetic system. In these conditions the brain's control over the sympathetic system is not synchronized with the conscious state.

So now, the parasympathetic system. In contrast to the sympathetic system, the parasympathetic system operates only through direct nerve innervation of the target organs. In other words, each target organ of the parasympathetic system has its own nerve switch.

Most importantly, the influence of the parasympathetic system on target organs is much more specific than the influence of the sympathetic system on them. In the sympathetic system, the same switch controls several target organs, while in the parasympathetic system, each target organ has its own switch. In summary: In certain situations, the brain will activate the general switch - via adrenaline - and in other situations, or in addition to releasing adrenaline into the blood, it will control the bodily response through specific switches. Back to sex After we have a deeper understanding of the autonomic system, we can talk about its function in the context of sexual activity. This understanding will explain why there is no connection between desire and bodily sexual arousal: women get wet and men get erections, and both can sometimes experience orgasm in rape.

Erections (of the clitoris and penis) and vaginal lubrication are caused by the action of the parasympathetic nervous system, which relaxes the muscles in the walls of the blood vessels in the genitals so that more blood flows to the organ.

In contrast, ejaculation and orgasmic contractions are caused by the sympathetic system (see previous post). When looking at the autonomic system in the popular and inaccurate view as if it has only one switch, the immediate question that arises is - as I mentioned before - how is it that the parasympathetic system, which is a system of calmness aka rest and digest, operates in a state of emergency such as rape? But now we know the answer: it's not a system with just one switch. The muscles in the walls of blood vessels in the reproductive organs are controlled by a specific nerve switch of the parasympathetic system. Thus, the parasympathetic system can cause erection and lubrication, including erection of the clitoris, in a state of excitement and even in a state of extreme danger. In other words, even in a state where there is a lot of adrenaline in the blood, when the sympathetic system is working at full speed, the parasympathetic system works locally on the smooth muscles around the blood vessels in the genitals and causes erection or lubrication. This explains how rape victims experience sexual arousal in their bodies: erection or lubrication. What is the control over the parasympathetic switch? Well, the answer is largely unknown. There are two types of involuntary ways of control: at the level of the spinal cord and at the level of the brain. At the level of the spinal cord, it is almost a reflexive response: a sensation comes from the genital organ to the spinal cord and a motor command is sent back. Thus, an erection or moisture in the vagina can be caused in this way without involvement of the brain. Many patients with spinal cord injury can have erection and even ejaculate by stimulation of their penis although they don't feel it. At the level of the brain, imagination, conscious sensation (sound, sight, smell, touch), and emotions are translated into activation of the autonomic system. There is an overlap between the emotional system in the brain and the control system over the autonomic system. There is another level of control in both types of operation. The commands from the brain and from the spinal cord reach their targets through relay stations: in other words, the nerve cell from the spinal cord does not activate directly, for example, the muscle on the blood vessel, but activates an additional nerve cell that then activates the muscle. A relay station always allows for further adjustments and adaptations to the activation. I believe that when we have a better understanding of the biological level of decision-making for activating the switch, we will also have a better understanding of the psychological explanation.

An open question is why does the parasympathetic defense mechanism work for men who are victims of rape. That is, I explained how it's possible, but why is it good for men to be able to have an erection during rape? Is it a result of a system that evolved for women? Is it because it gave an evolutionary advantage to rapists who had this trait? And what causes the different control in men: not every sexual situation causes an erection, unlike wetness that occurs in women in every sexual situation. What about ejaculation and orgasmic contractions? As mentioned, these are caused by the sympathetic system and we expect this system to operate in emergency situations. Therefore, getting ejaculation and orgasmic contractions during an emergency situation, like rape, is less surprising from a biological perspective. I explained how it's possible to have physical sexual arousal in a state of emergency, without a desire for sexuality and without pleasure. Both lubrication and orgasmic contractions are the result of involuntary, autonomous nervous system activity. So even if there is an orgasm during rape, it does not indicate a hidden desire for rape, pleasure, or a desire for sex. In fact, I showed that biologically, lubrication and erection are more surprising than orgasmic contractions during rape. In the past, it was not so clear and in cases of rape, usually involving women victims, they were asked in court if they had experienced an orgasm or physical arousal as if it was a sign of consent. Since 1978, according to the law in the US, an orgasm during rape cannot be interpreted as a sign of consent or willingness.

The experience of physical arousal (moisture, stiffness, orgasmic contractions) adds to the distress of the victims. They describe it as a betrayal of their own bodies and sometimes ask themselves if they wanted it on some level. Remember introspection, the brain may observe bodily reactions and infers emotional state, creating a sharp dissonance in this case. It is a disturbing experience that adds to the already difficult situation. Therefore, I believe that the knowledge I am conveying in this post should be common knowledge. I would be happy if you share it further.

I would love to hear YOURr comments, corrections, questions and in short: anything you want to tell me. Be ready for a big surprise: I don't know everything.


1. Arousal of Sexual Specificity, Psychological Science. (2013), Meredith Chivers, Psychological Science ref : The picture shows sexual arousal in the body towards videos of men or women in the 6 groups. For each group - regardless of gender and sexual orientation - arousal towards women was substracted from arousal towards men.

2. Prepared for Anything? An Investigation of Female Genital Arousal in Response to Rape Cues (2010), Kelly Suschinsky, Psychological Science

The Empirical Status of the Preparation Hypothesis: Explicating Women's Genital Responses to Sexual Stimuli in the Laboratory. (2020), Kelly Suschinsky, Archives of sexual behavior.

3. Specificity in the organization of the autonomic nervous system: A basis for precise neural regulation of homeostatic and protective body functions.

(2000) Janig, W., Habler, H. J. Progress in Brain Research

The picture shows a different physical response to different emotional states based on only 3 criteria, but more could have been added.

4. Emotion and the autonomic nervous system-a two-way street: Insights from affective, autonomic and dissociative disorders, (2016), Critchley, H. D, The Curated Reference Collection in Neuroscience and Biobehavioral Psychology.


6. A lecture of Prof. Meredith Chivers on "The Puzzle of Women's Sexual Orientation", 2016, youtube

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