This is your brain on SEX

The biggest difference between the male and female brain is that men have asexual pursuit area that is 2.5 times larger than the one in the female brain. Not only that, but beginning in their teens, they produce 20 to 25-fold more testosterone than they did during pre-adolescence.

If testosterone were beer, a 9-year-old boy would be getting the equivalent of a cup a day. But a 15-year-old would be getting the equivalent of nearly two gallons a day. This fuels their sexual engines and makes it impossible for them to stop thinking about female body parts and sex.

All thoughts, feelings, and bodily sensations you have correlate to specific nerve cells being activated. Orgasm, like all experiences, is brought about by electric impulses flowing along paths of connected nerve cells. Orgasm happens when specific pleasure pathways are turned on, while your defense pathways are turned off. All this happens by means of chemical messengers and the nerve cell receptors they bind to.

The limbic system is the seat of emotions, drives, impulses and desires – including sexual. It’s where you fall in and out of love…or lust. Due to the nature of the limbic system, you cannot will your feelings, emotions, falling in love, or staying in love, anymore than you can will your heart to beat, or yourself to digest a meal or sleep.

The central neurochemical player behind falling in—and out—of love is dopamine. Dopamine is the principal neurochemical that activates your reward circuitry, the centerpiece of the limbic system. Your reward circuitry drives nearly all of your behaviors.

At its most basic, this circuit is activated when you engage in activities that further your survival, or the continuation of your genes. Whether it’s sex, eating, taking risks, achieving goals, or drinking water, all increase dopamine, and dopamine turns on your reward circuitry.

You’re not actually craving ice cream, or a winning lotto ticket, or even a romp in the sack. You’re craving the dopamine that is released with these activities.

Dopamine is your major motivation, not the item or activity.

Dopamine drives us toward eating or orgasm, but the experience of the actual orgasm or eating chocolate arises from opioids goosing the reward circuit. In essence, dopamine is never satisfied.

There’s no such thing as a bad neurochemical or hormone, although either can become a problem when out of balance. Dopamine is absolutely necessary for your decision-making, happiness, and survival. Yet when it’s too low or too high (or when changes in its receptors alter your sensitivity), it can cause real problems.

Even small shifts in dopamine sensitivity or levels can have profound effects on how you see the world, or your partner.

Consider this: A menstrual cycle is generally 28 days of hormonal dominoes, but some women suffer from PMS often, others now and then, others don’t notice it. Same thing with the orgasm cycle. It’s there…and we know for sure that it lasts for at least 7 days in men, and for 15 days in both males and females of at least one other mammal. Yet the experience of those going through it can differ widely.

Subtle or not, these changes in our feelings can lead to many of the judgments that couples routinely make: “He’s not doing enough.” “She’s nagging me,” and so forth. Your genes want enough disharmony so that both of you will welcome new mating opportunities, whether or not you actually indulge in them. Why? Increased genetic variety in your offspring. There are no sexually exclusive monogamous mammals (or birds), even among pair-bonders.

Most addictions, or use of mood-altering substances and activities, kick in during teen years when we become sexually active. A Columbia University study found that sexually active teens use more drugs. One might think social factors alone lead to this correlation between drugs and sex, but when scientists studied hamsters, they found that sexually active hamsters were much more susceptible to amphetamine addiction than their virgin counterparts. This research brings us to another observation. Children, or pre-teens have yet to activate this dopamine roller coaster, and they generally possess a cheerful, optimistic enthusiasm for the simplest activities. Perhaps this is due to balanced dopamine.

Your limbic system is not equipped to understand that there can be too much of a good thing. It just keeps rewarding you to do the same unrewarding things. A “fix” just positions you for a continuous addictive cycle of highs, more lows, and a search for more highs. Many of us spend much of our sex lives caught in this cycle—with no obvious way out.

Humans, like virtually all mammals, are not naturally monogamous. This may not sound very romantic, but no mammals are sexually exclusive. (A few, such as humans, are socially monogamous. That is, they raise their offspring together.)

Oxytocin has various functions in the body, such as inducing labor contractions and milk ejection, but from evolutionary biology’s perspective, its main evolutionary function is to bond us to our children for life.

Oxytocin and dopamine are the yin and yang of bonding and love. Dopamine furnishes the kick, oxytocin makes a particular mate appealing, in part by triggering feelings of comfort. You need both acting on the reward circuitry at ideal levels to stay in love. In experiments, if scientists block either oxytocin or dopamine, mothers will ignore their pups.

Searching all the porn on the Internet might not seem like the most scientifically productive activity, but computational neuroscientists Ogi Ogas and Sai Gaddam did it anyway.

For their new book, A Billion Wicked Thoughts: What the World’s Largest Experiment Reveals about Human Desire, Ogas and Gaddam analyzed the results of 400 million online searches for porn and uncovered some startling insights into what men and women may really want from each other — at least sexually. I spoke recently with Ogas.

Why did you decide to analyze online porn searches?

I’m a computational neuroscientist. I view the mind as software. Most computational neuroscientists study higher functions like memory, language and vision. We wanted to apply the same techniques to a lower part of the brain, the sexual part.

So is “Rule 34″ true — that if you can imagine it, there’s porn of it?

When we first started, Rule 34 was almost a guiding idea. The Internet has every kind of imaginable porn; searches are going to reflect immense diversity. We quickly realized that [the data] didn’t really support that.

Even though you can find an instance of any kind of porn you can imagine, people search for and spend money and time on 20 sexual interests, which account for 80% of all porn. The top five are youth, gays, [sexy mothers], breasts and cheating wives.

Why are cheating wives so popular?

You’d expect that would not be something men would like to think about. It’s one of the top interests all around the world. Men are wired to be sexually jealous. And, certainly, men can fly into murderous rages, but simultaneously they’re also sexually aroused.

This is an example of what biologists call a sperm competition cue. Across the animal kingdom, when males see other males mating, it tends to provoke arousal. If he is going to compete with the other male, he has to produce more sperm. Human men also respond like this, if a man sees a woman — including his partner — with another man, he becomes more aroused.

There’s been a lot of concern that porn is getting more violent and more misogynistic and that the Internet is making it harder for women because porn makes men want more extreme sex. What does your research show?

It’s not at all more violent or misogynistic. We really looked at all porn searches. Truly violent pornography is extremely rare. It truly is rare and the kinds of people who watch it are a clearly identifiable group.

So why do we keep hearing that it’s getting worse and worse?

I wouldn’t say there’s a trend. It’s been pretty consistent. There’s lots of male dominant porn. He blackmails the woman into having sex; the professor seduces a student, they’re having sex to get cash for schoolbooks. We think all of these are creative variations to trigger male-dominance cues [which are sexually arousing to men].

Why do the themes of dominance and submission keep recurring?

Women are often aroused by women being submissive. It’s more complicated for women because of the separation between physical and psychological arousal. Women have very mixed feelings when [it comes to sexual submission]. But rape fantasies are extremely prevalent.

Obviously, that doesn’t mean that women want to be raped, but doesn’t the prevalence of forced sex in porn make men think that they do?

It’s not teaching men to be misogynistic; it doesn’t spill over into social life. It’s really no different from looking at large breasts. But women react to these psychological elements and understandably and accurately see them as a kind of misogyny.

However, we’re talking sex and arousal, not social politics. A rape fantasy doesn’t mean a woman really wants to be raped — it’s just something that turns [her] on [in the bedroom].

There are real concerns, though, that Internet porn will increase sex crimes because of the way it portrays things like that.

Anybody can do a simple thought experiment [to refute that]. In the late ’60s and early ’70s, feminists were saying that porn trained guys to be rapists. That was before home video, and there were probably only 100 different porn magazines in the country. You had to go to [sleazy places to watch porn].

Now there are a million websites where you can get it for free around the clock.

You would expect rape to skyrocket. There are more guys watching more porn more often. But, in fact, rape has gone down in America. Also, in Japan in the mid-’90s, they loosened their obscenity laws. Now rape is down there too. It certainly seems to be the case that more access to porn is associated with less rape. Rather than making people want to go out and rape, it satisfies the urge.

What types of porn are most popular for men?

It’s youth by a wide margin, like cheerleaders. But we were surprised to find that even though men prefer youth mostly, there’s also a very significant interest in porn with women in their 40s, 50s and even 60s. That’s called granny porn.

That’s fabulous for older women who seem to have been written off by evolutionary psychology. Seriously, though, the interest appears to be completely counter to evolutionary predictions that overt signs of fertility are crucial.

Yes, we found something that overturns narrow evolutionary psychology predictions. Some of our findings require other explanations than evolutionary ones.

What do women prefer?

Women prefer stories to visual porn by a long shot. The most popular erotica for women is the romance novel. That has more punch than any other kind of erotica. The second most popular would be fan fiction. This is something that has really exploded on the Internet. These are stories written by amateurs, mostly women, about characters from pop culture, movies, books, etc.

Is this the kind of thing in which Kirk and Spock from Star Trek would have an affair?

Yes, that’s called slash. Stories about two male characters are very popular. But the most popular fan fiction is about Harry Potter by a wide margin, followed by Twilight.

Why do women prefer stories and men prefer visuals?

There are two reasons. Both come down to fundamental differences between the male sexual brain and the female sexual brain. One of the most basic differences is that the male brain responds to any single sexual stimulus. A nice chest, two girls kissing, older women — if that’s what they’re attracted to. Any one thing will trigger arousal in a male.

Female desire requires multiple stimuli simultaneously or in quick succession. It takes more stimuli and more variety of these stimuli to trigger genuine arousal.

For a guy, the most common form of [masturbation material] is a 60-second porn clip. For a woman, it can be a 250-page novel or a 2,000-word story.

That’s the way to get multiple stimuli. Stories have greater flexibility to offer a greater variety of stimuli.

In male erotica, sex appears in the first one-quarter of the story [or film]. For women, it’s halfway in. There’s more time to develop the character before sex.

How else does male and female sexuality differ?

Another fundamental difference between men and women — perhaps the most important defining difference — is that in the male brain, physical and psychological arousal are united. If a man is physically turned on, he’s mentally turned on too.

With women, physical arousal and mental arousal are separate. [Research finds that women get physically aroused sometimes even when they find the situation disgusting.] The female brain is designed to be cautious, most likely because historically the woman who slept with the first guy she met might have a harder time raising children; he might not stick around. Women are designed to be cautious and gather more information.

That’s why fan fiction is all about exploring the emotions and character of the hero. In romance novels, the heroine learns about the secret inner life of the hero. That’s especially true in slash: that’s doubling up. There are two men — two masculine, strong alpha males who reveal their tender side. The emotional process of revealing true character is what’s so appealing to women.

Why would straight men want to watch lesbians, and why would women write stories about gay men?

[Straight] guys are turned on by lesbians because it’s a doubling of visual cues. And one psychological cue for arousal in men is female sexual pleasure. Seeing lesbians kissing doubles that too.

For women in slash fiction, it’s the psychological cues of a man’s character, stature, passion and emotional communication — slash doubles those.

What’s up with men’s interest in mothers?

It’s not so much that they’re moms, but that they’re older women. They are usually portrayed as aggressive and seductive. They are not timid. They’re quite confident and bold. Men who like that, like the idea of an innocent younger man being seduced or taught by an older woman.

Did you find evidence that porn is addictive?

We looked at individual search histories for half a million people using an AOL data set [which does not identify the users]. It seems to be less than 2% of people, among the people who search for porn, who have a significantly elevated number of searches.

And there’s a [shared] characteristic among these searchers: they search for a really wide variety of porn, which is atypical. Usually, people search for the same things over and over. But these people who search for notably more porn tend to search for [many different things].

Two things tend to show up in these searches, oddly: bestiality and granny porn. There’s clearly something different about that group. Having said that, there isn’t overwhelming evidence that porn addiction exists. Probably the best way to define whether it’s a problem is if you want to stop and you can’t.


Cupid’s Poisoned Arrow by Marnia Robinson

A Billion Wicked Thoughts: What the World’s Largest Experiment Reveals about Human Desire, by Ogas and Gaddam

Interview by Maia Szalavitz Thursday, May 19, 2011

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