Bad science

Making sense of the research

Out of Sync

Summary

Clitoral blood flow correlates fairly well with strong subjective arousal, about as well as penile erection does (roughly 50%).

The correlation between vaginal blood flow and subjective arousal is very low, around 10% in some studies.

Vaginal blood flow has been shown to vary with excitement and fear in a sexual context, but not arousal.

With high threat levels in a sexual context, there is an inverse relationship between clitoral and vaginal "arousal." I.e., the wetter the vagina, the less blood flow there is to the vulva and clitoris.

Dear Shakti,My husband and I have been doing tantra since we found your blog a year and a half ago, and we absolutely love it! (Thank you!) But we’ve run into a snag lately, and I'm hoping you can help.Here’s the situation: We’ve done all the preliminaries and I’ve given him a really nice lingam massage. I’m pretty turned on by that and I can feel the juices flowing. Then I get up on the table for my turn. He gives me a long wonderful massage, back and front. I’m meditating and loving the feel of his hands.Then he starts the yoni part of the massage and it feels great. I’m doing the inside focus thing to spread the charge around, and I’m really feeling good and starting to squirm and rock my hips a little, so he starts some oral, and that feels even better, and he starts to slide his fingers into me, then STOPS, and asks me what’s wrong.“Nothing, why?”“I am too!…. WTF??The first couple of times I just let it go. He did more oral, and eventually I got wet again, and on we went. But it keeps happening, maybe every third or fourth week, and he keeps asking me what he's doing wrong or what he needs to do different.He doesn’t believe me when I tell him I really am turned on. I feel like I’m halfway to an orgasm, but he keeps sayingand now I don’t know what to think. And at this point just thinking about it gets me tense during my massage and it’s been months since I had a really good “tantra high” or a full-body O.Help? What’s going on?Fara———Good question! It's quite common to hit a point when you are getting good at tantra and dry spells start to happen in mid-massage. The same thing happens to me and to a lot of other women who do tantra, and it can beconfusing!So I think this is something worth exploring in depth. And since we talked in my last post about male anatomy and the male nervous system, and the weird and complicated way the male orgasm works, I think this would be a good time to take a look at women’s anatomy and wiring, and how that can confuse us.First, let me give the short answer to Fara’s question: Your vaginalying to you. Or rather, it’s telling the truth, but it’s answering a completely different question, as we will see.What your husband needs to do is to pay attention to your words, your behavior, and your vulva,your vagina. If your clitoris is firm, if your outer labia are plump and full, if your inner labia and vestibule are redder and darker than normal, and if you sound and act like you’re aroused,And if you’re aroused and your vagina is still dry, well, that’s what lube is for.There’s an old Josh Billings quote that comes to mind: “It is better to know nothing than to know what ain't so.” It’s when we get a wrong idea firmly fixed in our heads that we go badly astray. We think we already know the answer, so we stop asking questions and we stop seeing what’s right in front of us.And in this case your husband “knows” one of those things that just "ain’t so." He "knows" that vaginal wetness is an accurate measure of arousal. It’s a very common belief, but it’s also quite wrong.Scientists who study these things made the same mistake for a long time, but have since learned that vaginal moisture is a very unreliable indicator of arousal. In fact, they even have a name for this phenomenon. They call itIn some experiments, vaginal wetness matches (or “concords with”) sexual arousal only around 10% of the time, roughly chance levels. So something else is going on.For a long time, researchers assumed the same thing Fara’s husband did, that vaginal moisture was all about sexual arousal. And that led to a lot of research results that just didn’t make sense until they finally figured out what is really going on.The story begins back in the 1970s with the invention of a cute little gadget called a "vaginal plethysmograph," a plastic probe the size of a tampon that is inserted into the vagina. It bounces light off the vaginal walls and measures the reflected light. More sophisticated ones also measure peak pulse pressure.Together, these two pieces of information provide a very sensitive record of even tiny changes in vaginal blood flow, which is what determines how wet you are. Normally, small amounts of moisture are produced all the time to keep the vagina flushed out and clean. When extra blood fills the vaginal wall and the pressure rises, a lot more moisture seeps through.There’s more to it than that, of course. There are two glands (called Bartholin glands) right at the entrance to the vagina that produce a different kind of lube. But most of the wetness you experience is just from rising blood pressure and blood flow in the vaginal wall, which increases “vaginal transudation,” the seeping of moisture through the inner surface of the vagina, which is what gets you wet.So we have this nifty toy that can tell scientists how much blood is flowing in the vaginal walls, and thus how much moisture is being produced. They already had a similar gadget, the penile plethysmograph, that measured changes in blood flow to the penis, so naturally they wanted to compare the two.And, of course, they assumed thatgadgets measured sexual arousal,Right? (Well, no. But we'll get to that.)And right off the bat they started getting weird results. Women who were shown pictures and videos while wired up with a plethysmograph responded in unexpected ways. Based on other studies, researchers expected that fear would inhibit sexual arousal. But what they discovered instead was that scary images with a sexual component – like violent rape scenes –vaginal wetness, even though the women reported not being turned on.In fact, pretty much anything with a sexual element caused increased vaginal wetness for women: images of nude men, images of nude women, videos of straight, gay, and lesbian couples having sex, videos of *bonobos* having sex! It seemed like *everything* even remotely connected with sex turned women on, whether they said they were aroused or not, and that scary, violent stuff involving sex turned women on the most, even if the women themselves insisted that many of the images had not been arousing.A pattern emerged. When the women rated how turned on they were by various imagery, their self-evaluations did not match what the plethysmograph said around 90% of the time. When men did the same experiments, they found fewer things arousing, and the match was about 50% – not perfect agreement, but a lot closer.So the (mostly male) researchers initially assumed that either the women were lying or else they were “out of touch with their bodies” and “didn’t know that they were aroused.” And so on. The assumption in a lot of the early discussion was that the plethysmograph toldand that the women themselves were unreliable reporters about their own brains, bodies, and emotions.For a while there was a lot of irresponsible reporting in the popular press about this, and at least one writer got a sensationalist bestseller out of it. But it turns out that the results simply show thatper se.Furthermore, a laboratory environment with strangers sticking probes in your vagina and then showing you pictures and asking for your responses is not exactly a safe, secure, familiar environment, so thealso triggered a significant amount of stress, making it seem that women were “aroused” by everything that was in any way sexual.This became a lot clearer when researchers began looking for other kinds of data. The clitoris is the actual physical analog of the penis, so if you want to compare sexual arousal in men and women, it makes sense to compare blood flow in the parts that match, the clitoris and the penis. So aplethysmograph was developed that measures blood flow in the clitoris.And it turns out thatblood flow “concords with” reported arousal much better than vaginal blood flow and lubrication. (I can’t resist the temptation to say “duh!” at this point. :) Furthermore,blood flow drops when a women experiences sexual inhibition – she sees an unpleasant or frightening scene – andblood flow doesn’t.So what is going on here?To begin with, you need to know that different parts of the nervous system deal with different kinds of situations. The(SNS) deals with threats and preparations for strenuous activity. When you’re scared or tense or keyed up – you see a car barreling toward you or you’re at the starting line of an important race – the SNS tells the adrenal glands to pump out adrenaline (epinephrine) and stress hormones like cortisol. It shuts down your digestion, reduces immune system activity, and halts other “maintenance” activities. It increases your heart rate and your breathing, and diverts blood from your visceral organs, like your gut, liver, and spleen, toward your brain and your big muscles. In short, it shuts down unessential activities like healing and digestion, and gets you ready to run, fight, or act fast and forcefully.The(PNS) normally does just the opposite. It slows down your heart and your breathing, it starts digestion back up, it redirects blood flow away from the large muscles and toward your internal organs, and it promotes all sorts of resting, healing, and maintenance behavior.A timely burst of adrenaline from the SNS can save your life, but too much chronic stress will kill you. One of the paradoxes of modern life is that we are physically safer than we have ever been, yet we carry very high loads of chronic stress, keeping the SNS turned on all the time and not giving our bodies time to rest and heal. When you meditate, one of the most important things you are doing is turning your SNS off and your PNS on.It’s the balance between these two parts of the nervous system that controls an awful lot of what goes on automatically in our bodies. However, the balance is not a simple seesaw relationship. There are times when the PNS is signaling to one part of the system to relax while the SNS is signaling to other parts to prepare for action.And sex is one of those times when you can be getting signals from both systems. The PNS gets you aroused and ready for sex. The stronger that activation gets the closer you are to an orgasm. Then a sudden spike from the SNS triggers your orgasm, canceling out the PNS signal and leading to an abrupt decline in arousal.If you're a little bit stressed or scared, the signal from the SNS can make it a bit harder to become aroused, but sex can still happen. Interestingly, it can also make it a bitto have an orgasm once you're turned on, because the SNS signal is already elevated. But the orgasm you get happens at a lower level of arousal, so it feels less intense.But if you'restressed or scared, the signal from the SNS can be too strong from the beginning, and you won’t ever get aroused in the first place.How does this affect the vaginal moisture puzzle? Well, we can get a clue about this by looking at the other gender. With men, the PNS is in charge of erection and the SNS is in charge of ejaculation. (The med school mnemonic is:A man needs to be relaxed enough to get an erection. Too strong a signal from the SNS (from fear, stress, anxiety, or simply excitement) will cancel out the PNS signal, and prevent the erection from happening. And even if heget an erection, the elevated SNS levels can cause early ejaculation. This is why performance anxiety can cause either erectile dysfunction or premature ejaculation, or sometimes both.The clitoris and the labia are the female analogs of the penis and the scrotum, so it is no surprise that they are turned on and off by the same parts of the nervous system. The PNS signal sends blood flow to the external genitals, causing the penis to become erect in the man and the clitoris and labia to become engorged in the woman. A surge in SNS shuts down the extra blood flow at the end, during orgasmThis is, incidentally, why the congested feeling in the genitals fades away much faster after an orgasm than it does if you never reach the orgasm point. Men call this "blue balls," but women who have had prolonged sex play with no release can experience the same kind of discomfort.But if a woman experiences too much stress, anxiety, or fear, and SNS activity is too high too early, this will shut down the blood flow prematurely and prevent physical arousal from occurring in the first place. High stress, anxiety, and fear can prevent female arousal in the same way they keep men from getting erections.There’s no obvious internal correspondence in women to the man’s “Emissions Phase,” involving the vas deferens, the seminal vesicles, the prostate, and the other glands that produce semen. But the vagina occupies the same general region of the body as the man’s internal sexual parts, and the same nerves serve both sets of organs. And just as it is the SNS that gets a man ready to ejaculate, it is the SNS that stimulates blood flow to the capillaries in the vaginal wall.But wait! The SNS responds to. Why would it be in charge of getting the vagina ready for sex?Well, actually, the SNS responds to many things, including the anticipation of strenuous physical action. When you’re at the starting line, waiting for the gun to go off, the SNS is pouring adrenaline into your system and getting you ready to run. You don’t have to be scared, you just need to be excited and primed for action.And most of the time, this works just fine for sex. If you feel safe enough and you'returned on and ready to go, your PNS gets your clit and labia swollen and aroused. And if you’rein a sexual context, moderate SNS activation gets your vagina ready to go. Since most sex involves a mixture of relaxation, excitement, and arousal, that usually works fine.But it also explains the contradictions that happen when the two signals get...consider what happens when you have high stress/fear/anxiety and low arousal in a sexual context. Your SNS is pouring out adrenaline and your PNS is shutting down the unessentials.This is what typically happens in a real rape situation or threat (not a rape fantasy). The vagina gets wet, the clitoris and labia remain flat, and the emotional centers of the brain are signaling fear or anxiety, not sexual desire.Many rapists try to excuse their actions by saying that the woman's vagina was wet, so "she really wanted it."Some scientists speculate that this way of wiring up the nervous system evolved specifically to protect women from injury during nonconsensual sex. Throughout history and prehistory, women have often been expected or forced to have sex whether they wanted to or not, without any consideration of whether they were turned on by their partners.If the vagina only became lubed when a woman was genuinely aroused, these women would have had frequent dry sex and would have been at constant risk for abrasions and tears that created openings for vaginal infections, pelvic inflammatory disease, sterility, and death. From an evolutionary point of view, it is far safer to have lubrication respond tosexual context, particularly a scary one, than to make it depend on genuine desire.consider what happens at the other end of the spectrum, when stress/fear/anxiety are extremely low and sexual arousal is high. This is Fara’s situation, and also mine and that of many other women doing tantra. We have deliberately created an environment of total safety. We take a long relaxing shower or bath, we meditate, we get a long, luxurious full-body massage from someone we trust absolutely.We do this intentionally because it produces some very special effects during sex that are quite wonderful. But it can definitely mess up the internal signals that usually activate both arousal and the production of additional vaginal moisture.So... what is happening internally when we are both aroused and totally relaxed? Clearly in this situation we're going to have high PNS activation and near-zero SNS activation. That means no adrenaline or cortisol, SLOW heart rate and breathing, low blood pressure, and limp muscles. And, in particular, high PNS/low SNS means lots of blood going to the clit and vulva, and very little going to the vagina.Compare that to having sex with a new guy, back when you were dating. Most likely, your heart was racing, you were breathing hard, your muscles were tense, and both the excitement and the physical effort sent your blood pressure way up.Let's face it, beingrelaxed during sexual arousal isn’t normal. And when we create this abnormal situation, it can send the wrong signal to the vagina. There needs to be at leastSNS activity for blood flow and pressure in the vaginal wall to be high enough to create natural lubrication.This is not a problem unless you let it become one for you. Keep in mind that we aredoing something unnatural here by having sexual arousal in a situation with no stress. Call it “zero-adrenaline sex.” It's one of the keys to what makes tantric sex magical.Because adrenaline acts in some ways like an anesthetic, it blocks a lot of the intense pleasurable sensations that happen during sex. Adrenaline, cortisol, and other stress hormones also reduce oxytocin production, and particularly the use of oxytocin in the brain to reinforce the couple bond.So one of the main goals of tantric sex is to minimize adrenaline and maximize pure sensual pleasure. And in the process we are quite likely to get below the minimum SNS threshold for producing natural vaginal lubrication, even when we’re very turned on. We just need to recognize that for what it is … a side-effect of feeling very safe and relaxed, which is exactly what we’re trying to achieve.After the first few times this happened to me, we started using lube automatically at the start of yoni massage whether I needed it or not. And that solved the problem. Since we use coconut oil for both massage and lube, this requires no extra effort on Z’s part. He just scoops a little extra on his fingers before he goes exploring.Some women never have this problem, even though they are successful in getting into a deep state of relaxation during yoni massage. And of course I have wondered why some women do and some don't. It’s possible that differences in resting heart rate and blood pressure have some effect. Since I’m in the low-normal range for both, that would make sense of why I do go dry in mid-massage. It’s quite possible that someone with a somewhat higher resting pulse or blood pressure would never have the same problem.Another possibility is that having sex, or receiving a yoni massage, still feels somewhat risky or dangerous for some women who were brought up in sex-negative households. Perhaps a woman has discarded most of her childhood indoctrination, but still has a twinge of feeling that sex is bad, or that oral sex is "dirty," or that being naked on a massage table and letting a man devote himself to her pleasure is wicked or shameful.It may even happen in a good way, giving her a wicked little thrill! But even if it's below the conscious level, the awareness that she's doing things she knows her parents or religious preceptors would disapprove of might providestress, tension, or rebellious excitement to trigger her SNS enough to get her wet.As Emily Nagoski points out in Come As You Are , "arousal nonconcordance" (the lack of correlation between vaginal lubrication and actual sexual arousal) is quite well documented. Some data points:Sexual encounters in real life usually involve a combination of excitement, anxiety, and sexual arousal. That's especially true for single people. Sex with a comparative stranger always involves some excitement and some anxiety – about him, about your body, about the circumstances, about what your mother or your friends would think, about all kinds of things.In a sexual context, the stress or excitement gets the juices flowing in the vagina, even if you are not particularly aroused. But assuming you are both somewhat stressedaroused, the stress gets blood flowing to your vagina, the arousal gets blood flowing to the clit and vulva, and everything stays reasonably in sync.In a sexual endangerment situation, a woman can be scared and neither mentally aroused nor physically aroused in terms of her clit and labia, but she can still get strongly lubricated because her heart is pounding and her vaginal blood flow is high. Her vulva and her vagina are completely OUT of sync.If a woman is feeling completely safe and relaxed when she is having sex, she may experience the opposite - being completely turned on, her clit and labia swollen and throbbing, but little or no moisture inside her vagina. (Which is why there's a bottle of lube on the bedside table in many long-term relationships.)NOT being wet does not necessarily mean you are NOT turned on and ready. Sometimes it just means you are feeling safe and relaxed with a guy you really trust and you're not doing anything that makes you feel naughty or "transgressive."Boys are taught that when a girl is "wet" it's a sign of arousal. This can lead to serious crossed signals during sex. As noted, it is common for a rapist to claim that his victim "really wanted it" because her vagina was wet.Women can fall into a similar trap. If you believe that “your vagina doesn’t lie,” then you think you're turned on by things that reliably get you wet, whether you are mentally aroused by them or not.For a lot of woman who have never had good sex, that means rough sex and BDSM. Even if that kind of sex is not enjoyable for a particular woman, she may reason subconsciously that that’s what her body needs, because that’s the only kind of sex that reliably gets her wet.The problem with that is that vaginal wetnessmeasure desire or arousal. It's a reflection of stress, fear, and/or anxiety in a sexual context. This isn't necessarily bad. A little bit of fear, for example, is a component of many things people enjoy – roller coasters, scary movies, imagining sex with a really hot guy. But women who rely on vaginal wetness to tell them what turns them on can get trapped in a situation where they only want to have sex in situations where they are stressed or scared.Fear/stress/anxiety and arousal do often go together – a rape fantasy, for example – but confusing the two puts us in the position of condoning real rape and blaming the victim because she got wet when she was experiencing real fear.Human beings vary enormously about sex and what we think are turn-ons. Some women are strongly attracted to high-adrenaline sex, and they seldom notice a problem with lubrication not happening when they are turned on. Women who are more attuned toward slow, sensual sex are more likely to notice the difference, since they can get highly aroused without being wet.But any woman who has found her panties soaking wet after a real rape or rape threat, one that was terrifying and not at all sexually appealing, has reason to understand that arousal and wetness are not the same thing.