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“If you stroke the thermostat just like so…”starmanseries via Flickr

Have you ever stopped to consider how sex is like a thermostat? Sex may not sit in a beige box on your wall (or it might, no judging) but there are some striking similarities. The common ingredient is feedback.

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Both sex and your thermostat depend on feedback loops. They work like this: 1) An action produces a result. 2) Information about the result then influences the subsequent action. 3) Repeat. Your thermostat, for example, measures the air temperature, then turns on or cuts off when it crosses the set point. Action of the heater or air conditioner influences the temperature, which influences future action1. And so on, forever—at least until you need new batteries.

People often don’t think about sex as a feedback loop, but it is perhaps one of the most powerful and successful loops of all time. Sure, a hundred things can and do go wrong, but on the whole, people continue to have sex. In fact, it’s very difficult to stop them. And that’s pretty much the point. 

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Sex uses positive feedback. The “positive” part doesn’t mean happy or good; it means that the output intensifies the input. You do something. You like it. You want to do it more. Or, in a bit more detail, stimulation of the erogenous zones is relayed to the brain, which registers pleasure, encouraging you to continue the pleasurable activity, which leads to more pleasure, and so on, until orgasm shuts the whole thing down. 

The body is chock full of feedback loops—loops for pain, growth, repair, movement, balance, hunger, and on and on. The scientific record is brimming with discussions of biological feedback, and therapists certainly encourage to communicate effectively, but the systematic study of sexual feedback is woefully thin. This blind spot is unwarranted considering how common sexual problems are, and those problems can often be traced back to flawed feedback loops . 

If you are having a sexual experience solo, the feedback loop is simple. You do more of what feels nice and less of what does not. But sex with another person can create an imperfectly closed loop—the information doesn’t get fed back to properly affect the subsequent action. It can be what engineers call a “noisy” system. 

The trouble is, when two (or more) people are involved, feedback is based on secondary clues. Like that thermostat installed right by the drafty window, if the signals coming in are not spot on, the experience is going to suffer. In general, it’s assumed that certain genital responses (such as increased blood flow and lubrication) are indicators of sexual arousal. But lab studies show that people sometimes show such genital responses even when they report no arousal, or even disgust. The opposite mix-up—subjective sexual arousal without genital response—is possible as well. Interestingly, several studies have found (pdf) that “correlations between sexual feelings and genital responses [genital feedback] are lower in women than in men.” In a 2010 meta-analysis, the prominent sexuality researcher Meredith Chivers and colleagues concluded, “In almost all of the comparisons, men produced higher subjective-genital correlations than women.” The sexes seem to differ in terms of interpretation of physical feedback. Women’s subjective experience is more strongly influenced by context—am I safe? How do I feel about this person? Is this socially acceptable? This means that in women, the feedback loop may be noisier, with multiple inputs, and more chances to derail. 

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But a healthy sex life doesn’t only depend on positive feedback: We also need negative feedback after sex so that we do other things too—like eat and sleep and go to work.

Because the body is so full of interacting feedback loops, the study of biological systems is incredibly complex. We still don’t fully understand the incredibly important phenomenon of orgasm, or why sex between the same people can get boring. Unfortunately, sex is much more complicated than your thermostat. Also, more difficult to do research on.

Still, there have been some efforts to systematically study sex so we can better figure out how it works. One way to get at the problem is to stick people inside an MRI, tell them to masturbate to orgasm, and watch what happens in their brains throughout the process. Researchers hope that by watching blood flow through the brain in real time, they can learn more about when, how, and why people have orgasms. Researchers want to better understand the feedback loop. They need to know how the body responds to stimulus working up to and during orgasm, and what changes as it returns to normal.

Some researchers hope to use such MRI feedback as a kind of therapy. If people who have a difficult time reaching climax can watch their brains as they try, so the thinking goes, perhaps they can learn better how to get there. The technique, called neurobiofeedback, most commonly uses EEG, and it is being tried to treat everything from attention and behavioral disorders to migraines. It has also received a fair share of criticism. At its heart, neurobiofeedback seeks to close the feedback loop so the system (in this case a human) will run more smoothly. Better feedback loops might mean better sex.

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But a healthy sex life doesn’t only depend on positive feedback: We also need negative feedback after sex so that we do other things too—like eat and sleep and go to work. Negative feedback is a major part of many of the body’s regulatory systems. So, for instance, if your body’s blood pressure shoots up past normal levels, your brain controller will take steps to bring it back down. Your thermostat is another example of a negative feedback loop.

In sex, improperly functioning negative feedback may lead to hypersexuality—the inability to inhibit sexual fantasies, urges, and behavior. Though the American Psychiatric Association does not currently classify hypersexuality as a disorder, several researchers have supported its addition to the standard classification (pdf) of mental disorders used by mental health professionals in the United States: the DSM. According to an article in the journal Psychiatry, consequences of compulsive sexual behaviors can include increased risk for STDs, financial loss, greater risk of illegal activities, strain on families and interpersonal relationships, warped understanding of intimacy, and personal shame and guilt. Many scientific articles point out parallels between sexual impulse control and substance abuse disorders

It would be nice, wouldn’t it, if like a thermometer we could just open up a person and watch how they work? The complexity of biology is staggering, but I think it is no coincidence that similar problems tend toward similar solutions. Maybe sex therapists should invite an engineer for a consult. Maybe engineers should branch out a bit and pay more attention to sex, one of the most deeply human questions. And the next time you see your thermostat, give it a little wink. You know what’s going on in there.

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1) What I described is called a closed feedback loop. Information about the output is relayed back to the input, which then adjusts the output. But not all loops are closed. In an open loop, that second arrow is broken or absent. One example of an open loop is early vehicle cruise control. In the first iterations, the throttle simply remained at a fixed position. This worked fine on flat roads, but on a hill the car would slow as it climbed, then accelerate going down. It was terrifying. Today’s cruise control uses vehicle speed as feedback—a closed loop. 

Jenny Morber is a freelance science writer based in Fairfax, Virginia.

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