Why we love back rubs, chili peppers and the sex from “50 Shades”: David Linden on the strange science of touch

The author tackles some of the biggest questions from his new book: “Do I want this? Is this sexual? Is this good?”

Published February 14, 2015 11:00PM (EST)

        (<a href='http://www.istockphoto.com/profile/xelf'>xelf</a> via <a href='http://www.istockphoto.com/'>iStock</a>)
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I have this annoying tendency -- a tic, really -- to sit and stroke the same piece of hair over and over again throughout the day as I work. I run the same half-inch-wide collection of strands at the bottom layer of the back of my head between my right ring and middle fingers, my thumb tracing beneath, for hours every day. It's awful, but it helps me concentrate -- it also feels good. But if ever someone else tries to repeat the movement on my head, it never feels right; usually the sensation is enough to make me shudder and jerk away. That's because, despite my weird hair tic, I am a normal human -- one whose hairy skin has special nerve endings at the base of her hair follicles that are sensitive to different touches, whether they're too fast or too slow or just right.

The "just right" sort of touch -- a caress -- is much more important to our survival than many people often realize, argues neuroscientist David J. Linden in his new book, "Touch: The Science of Hand, Heart and Mind." Linden suggests that although we might be quick to say we couldn't live without the senses of sight or sound, it is actually touch that is almost inconceivably integral to our lives. Without the sensation of pain, for instance, our bodies would be at risk constantly; we wouldn't remove our hands from hot stoves or notice our skin break when our clothes are too tight.

But what would happen without the sensation of pleasure -- without the emotionally charged touches of family, friends and lovers? What would happen without sex? These touches, Linden notes, are also vital, both to our physiology and to our humanity. Salon spoke with Linden about his book and all the touches he highlights in it -- especially the sexy ones. Our conversation -- about sexual masochism, social touch deprivation and the similarities between having an orgasm and eating falafel -- has been condensed and lightly edited for clarity.

In the sexual touch chapter, there are two charts where you talk about the pleasure experience, for eating and for sex, and you say that sex is a lot like other touches or other activities as far as how we experience pleasure. Can you explain that a little bit?

I think we think of sexual activity as being something entirely outside the realm of everyday life, an entirely unique experience. But it is not entirely so. The example I use is that you’re hungry, you’re walking down the street. You smell something delicious, you think about eating it. You’re getting some pleasure out of anticipation. You order it, you’re smelling it even more, you’re seeing it even more, you’re seeing other people eating it. You’re getting more anticipation. You’re hungry and then you take that first bite and the first bite is the best. As you continue to eat and become sated, your pleasure responses become smaller and smaller until the last bite before you quit. I contrast that with a case of a couple -- I use an example of two women but it doesn’t really matter, it could be anybody. As sexual activity occurs, that’s where things differ between food and sex in the sense that with food, you have some build-up of pleasure with the anticipation and with sex you have build-up of pleasure with the anticipation. But then with food, the very first bite is the best and with sex, of course, the very first sexual contact is usually not the best. Usually things build to orgasm and I think most people would say that if they have an orgasm, that is the moment where they feel the most intense pleasure. So food and the trajectory of pleasure over time with food and sex are not precisely the same, but they’re not entirely different.

There was a video that went around a few months ago about a man who suffered from persistent genital arousal disorder (PGAD), which you describe in the book. What is going on when someone experiences that?

The truth is that we don’t entirely know. It really is much more of a phenomenon in women than it is in men, and in men it has a slightly different name, which is priapism. The issue is different because [with priapism] you can have a persistent erection that does not make you feel an urge to achieve orgasm, whereas with PGAD, which is the dominant term for women, there’s not just some physical manifestation, like you lubricate or your clitoris or your labia become engorged with blood. It’s that [those manifestations] come together with a strong urge to achieve orgasm that is independent of any romantic or sexual feeling. It’s more like an itch and the compulsion to scratch than anything else. It has been associated with certain medical conditions like obsessive compulsive disorder and restless leg syndrome. There is some success in treating PGAD with some of the same treatments that are used for obsessive compulsive disorder: antipsychotics, occasionally antidepressants. But in most women who suffer from PGAD these drugs actually don’t help.

So “50 Shades of Grey” comes out on Valentine’s Day, which means, naturally, I have to ask about the overlap of pleasure and pain during intercourse. It makes me think of your discussion of chili peppers and how they’re rewarding to eat because they’re threatening. Is it a similar thing for pain during sex?

I think you’re absolutely on the right track. We know that there’s a fraction of people for whom pain can be rewarding and can enhance or even take the place of sexual contact. People can make psychological interpretations of this, about control, but I think that doesn’t really go very far towards the real explanation. Here’s what I think is fundamentally important in understanding masochistic sexual practice; I think it’s twofold: One is that both pain and pleasure fall under the larger category of things that are salient. In other words, things that you must attend to because they’re important for future life. Salience is itself rewarding. Part of the reason we know that is that the pleasure circuit is mediated by neurons in a region of the brain that uses the neurotransmitter dopamine. However, mixed in with those neurons there are other neurons that seem to be activated by pain -- and these are also dopamine neurons and they’re also in the pleasure circuit. To me what this tells us is that a little bit of salience, a little bit of, “Hey, we’ve got to attend to this because this could be important for the future,” is itself rewarding. When that is blended with the pleasure of sexual practice, for some people this can make the pleasure that much more intense. Now the other aspect that I think is relevant is that essentially when you engage in masochistic sexual practice, you’re training your brain because you’re learning that this pain is actually going to be OK. In the end, you’re not going to be dead, you’re not going to be scarred in most cases. In a way it is a little bit like cognitive behavioral therapy, the way someone might train themselves not to be afraid of heights or afraid of crowds.

You quote at some length from Naomi Wolf, where she talks about the differences in vaginal and clitoral innervation to explain individual women’s differences in experiencing pleasure. I’m curious how adequate that is as an explanation for individuality in sexual pleasure?

The problem is we don’t actually know if it’s true at all. It’s a plausible idea, but the truth is, these are tiny little nerves and they’re below the resolution of our ability to measure them in living people. So an MRI machine can’t see these tiny little nerve branches that innervate the clitoris and the labia, they’re too small. The problem is you can find them in a cadaver, but usually you don’t have a cadaver that you previously asked about what kind of sexual sensations they like. In other words, what she puts forward is an entirely plausible hypothesis that variations in the exact locations and density of nerve endings could account for at least part of the variation in why some women might like penetration more and other women not, or play around the anus and other women not, things of that nature. The other thing you should keep in mind is that it’s not just something that you can see in the structure of nerves. Let me give you an example: When you were in science class, did you ever do this experiment where you lick a piece of paper and some people taste incredibly bitter and other people can’t taste it at all? If you just look at people’s tongues, you can’t tell the difference between who is going to taste the bitter and who isn’t. That difference is a mutation in the bitter receptor; it’s a difference in the DNA that leads to a mutation in the bitter receptor and allows for different perceptions of bitter. Likewise, there could be genetic variation between women, or between men for that matter, that produces different aspects of sexual sensation, which you can’t see in structure of nerves.

So, I recently did two separate interviews about circumcision. I spoke with one man who was circumcised at age 21 and two other men who are foreskin restoration activists. Reading the book made me really curious about foreskins and the difference in sensation for men who are circumcised and men who are not. I was wondering if you could speak to that.

Well, I can’t speak to it in specifics, but let’s make an analogy. If you cut off your finger when you’re an adult, let’s say when you’re age 20, and then you look at the touch map in the somatosensory cortex of the brain, there’s a map and you would have the hands with the different fingers and the thumb on it. What you see is very slowly over time the fingers adjacent to the one that was removed will take over the part of the brain that used to handle touch sensation for the finger that got cut off. So imagine that if you’re a boy and you’re born and your foreskin is cut off -- there’s a part of your touch receptors of your somatosensory cortex that was dedicated to the foreskin and now it’s gone. So probably now your brain is rearranging as a result of that. I think the important thing to realize is that the brain can subtly rearrange not just from chopping stuff off, but even from experience. If you are a mother and you’re nursing, then the representation of your nipples will get larger as a consequence of having them suckled. When you’re done breast-feeding, your representation of your nipples will shrink back. Your brain is a little bit plastic in how it represents sensation, a little bit changeable, both by drastic things like a lack of a part of the body, as well as just the way you behave with it.

At the very beginning of the book, you talk about socially reinforced touch deprivation, and you cite examples of people tipping more if they’re gently touched by a waiter, because we need those social touches. How do we bridge that gap of not really touching each other enough, but also engaging in certain sorts of touching that are violating and nonconsensual and problematic (specifically, sexual assault)?

I think we just have to be realistic about this in the sense of: What are you going to be able to legislate? And who’s going to pay attention to your rule? If someone is a sexual predator and you’ve got a no touch rule, they’re going to just violate it anyway. The people who are going to pay attention to the no touch rule are not the predators. They’re the people who are going to want to bond and are going to be doing appropriate social touching. I think the larger point that’s crucial here, and it keys into exactly what you’re saying, is that the way we experience touch is totally dependent on context. The example I use in the book is, imagine an arm around your shoulder from your sweetheart when you’re feeling very loving and connected. And then imagine that same arm around your shoulder when you’re in the middle of an argument that’s not resolved. It’s not just that they feel the same but on reflection you feel differently about it; they actually feel different. Imagine an arm around your shoulder from a domineering boss or someone hitting on you or your best buddy. They all feel different. The reason they feel different is because the parts of your brain that are involved in computing social context: Do I want this? What’s someone’s intention? Is this aggressive? Is this sexual? Is this affiliative, is this good? All that information actually flows from these higher parts of your brain to the somatosensory cortex and changes it so that it alters the way it actually feels. You could be touched the exact same way and it’s going to feel differently in the very first moments depending upon the context.

By Jenny Kutner

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