Porn watching, as a hobby, has risen to record popularity. But scientists are still trying to figure out what watching all that porn actually does to users — and to society at large. There are, however, a few things we do know.

The moment a person looks at an erotic image, the reward system in their brain switches on. This circuit includes the ventral striatum and orbitofrontal cortex, both of which help elicit the good feelings you get when you do something good. And while there are a handful of other brain areas associated with the experience of viewing pornography — which we’ll explore in a moment — they’re all involved in a pretty similar way. As people’s brains reward them for watching porn, their brains learn, over time, that porn is a reliable way to seek good feelings.

Let’s explore how that process manifests as different behaviors across various brain areas.

Reward-Seeking Behavior

A 2016 functional magnetic resonance imaging (fMRI) study of porn viewers in the journal NeuroImage showed elevated activity in the ventral striatum when male participants viewed something sexy, suggesting that the brain’s reward system was releasing dopamine. Meanwhile, analysis of the participants’ self-reported porn watching habits showed that many of them reported subjective symptoms of porn addiction. When comparing the fMRI data and survey results, scientists found that the degree of ventral striatum activation correlated with the degree of porn addition each participant reported via questionnaire. In other words, people who reported signs of porn addiction experienced greater degrees of ventral striatum activity when they looked at porn.

In this image, we can see the ventral striatum, at the center of the image, lit up in the brain of a subject while he looks at something sexy.

ventral striatum
Researchers in 2016 found a positive correlation between self-reported pornography addiction and activation of the ventral striatum when viewing erotic images.

Emotional Motivation

The amygdala, a part of the brain involved in emotional behavior and motivation, may also be activated when viewing pornographic materials, according to Mateusz Gola, Ph.D., a neuroscience researcher at the University of California, San Diego.

Research on people with compulsive sexual behavior suggests that altered connectivity and increased activity in the amygdala are linked to reward-seeking behavior. In particular, they reflect a change in a person’s “appetitive conditioning” — in which their biological response (activation of the reward pathway) seems to be greater than normal in response to sexual stimulus. While the people involved with this research didn’t exhibit addiction to porn per se, the reward-seeking motivation in their brains read similarly.

Problematic Behavior

Now, looking at porn once in a while may or may not have any significant effects, but researchers have identified reasons to worry about some people who look at it frequently. Though researchers behind a 2017 study found that many porn users are compulsive, distressed, or both, they cautioned that these findings, as well as studies of porn use, are in their early days. In the paper, the University of Montreal’s Marie-Pier Vaillancourt-Morel and her colleagues noted that, even though some of their subjects reported negative sexual outcomes and attitudes related to porn use, they were in the minority.

“Despite strong social pressure for rapid closure, we should be cautious before concluding that pornography use is universally harmful or beneficial,” write the authors. “Our contribution shows that subgroups of pornography users report differential sexual outcomes. Most of our sample was composed of recreational users reporting positive sexual outcomes, including higher sexual satisfaction.”

Structural Differences

Another study showed that the volume of gray matter in a person’s right caudate (in the forebrain) was negatively correlated with how much porn they view. In other words, high-volume porn viewers had less gray matter — but that’s not to say that the relationship between the two is causal. Since many people start viewing porn around age 10, when the brain is still developing, there is no way to tell whether structural brain differences are a consequence or a cause of porn use.

brain images porn
Scientists found a negative correlation between the volume of gray matter in a person's brain and the amount of porn they watched. It's not clear whether this is a cause or consequence, though.

Primed for Porn

Problematic pornography users (PPUs), according to Gola, seem to be uniquely primed to respond to erotic stimuli: In April 2017, he and his colleagues published one of the first neuroimaging studies examining how the brains of PPUs respond to erotic stimuli compared to those in the healthy control group. In an fMRI machine, the subjects played a discrimination game that, if played correctly, rewarded users in the form of money or an erotic image.

Both the control group and the PPUs reacted more strongly to erotic rewards than monetary ones, but ultimately both groups responded to these stimuli with comparable levels of brain activity, especially in the ventral striatum. It was surprising for Gola, who thought that the PPUs would react more strongly; all porn viewers, it seems, react the same way to porn when they’re presented with it.

But he was most surprised when he tweaked the test so that “cue” images would tell participants when a pornographic image was on its way. This time, PPUs reacted much more strongly to erotic cues than the control group. “PPUs have much more elevated ventral striatum responses than non-problematic users,” Gola explained to Inverse. Taken together, his results suggested that people who view porn compulsively seem to have much stronger neurological reactions than regular viewers to the suggestion that porn is on the way.

porn study methods
Mateusz Gola and his colleagues found that while problematic pornography users and control subjects reacted similarly to porn, the problematic pornography users reacted much more strongly to a cue indicating porn was on its way than the control group did.

“Sometimes they have this urge to watch pornography that’s so strong they can’t hesitate, and they just start watching,” Gola explains. “For many people, cues are things like staying alone in the office or at home. He’s triggered, and this motivation is very strong. We had patients for whom sitting in the chair they used to watch pornography and masturbate was very triggering.”

These results suggest that people who have trouble controlling their porn habits may actually experience a uniquely powerful response to triggering stimuli. Not only that, once the stimulus primes their brains to get ready for porn, they are very quick to respond.

“Addiction” Might Be too Simple

So, what does all this mean for the scientific study of porn viewers’ brains? Sure, porn is a very strong motivator for people who scientists label as PPUs, or compulsive users. But is it the social ill that groups like Fight the New Drug or Your Brain on Porn might lead us to believe? Gola says it’s not quite that black and white.

“It’s definitely a topic that should focus on the importance of scientists. A lot of studies focus on analogies to other addictive behavior, [like drugs or gambling],” he says. His research, which borrows methodology from gambling studies, has suggested that people who engage in porn-watching behaviors in a way that could be called addictive may experience similar neurological processes as gamblers. Nevertheless, he cautions that the scientific understanding of “addiction” is changing, and as it does it’s important to keep the scientific end goal — treatment — in mind.

“We would rather try to figure out how to help most efficiently, not how to label the problem,” Gola says.

To this end, he points to the incomplete quality of the porn research that’s out there today. He says the best way to help us understand more fully whether porn changes the brain or whether people with certain brains prefer porn is to do long-term studies that combine surveys and brain scans. “We need to start collecting longitudinal data from a representative sample of Americans: how [pornography use] changes, how many people experience troubles because of problematic pornography use. Same with brain studies: We need to start tracking people and seeing what’s going on,” he says.

Clearly, we have a long way to go before we can answer some of the big questions. Is porn addictive? Maybe. Maybe not. Does porn change your brain? Maybe. Maybe not. Are compulsive porn users’ brains different from other people’s? Kind of. For now, that’s pretty much the only effect we’re certain that porn has on the brain. But as porn becomes increasingly widespread and accepted, there’s no doubt that we’ll be learning more about its effects on our brains soon, whether we want to or not.

Photos via Brand et al, Simone Kühn and Jürgen Gallinat, Gola et al, Flickr / nats (1, 2)