This article was originally published in Le Point on 21.09.2025
They might not quite qualify as windows to the soul, but human nipples can still reveal a surprising amount of information about the hidden mental states of those they’re attached to. While we can’t literally see another person’s private feelings, what we can see (especially in France but more on that shortly) are their erect nipples. Alongside other obvious cues, such as shivering and goosepimples when it comes to feeling cold, a person’s subjective states are frequently betrayed by their stiffened mammary papillae.
There are multiple triggers for nipple erection in humans—a chill in the air, stress, fear, and for women, of course, lactation. But horniness, too. And it’s the sexual connotations of nipple erection—or at least, the perceived sexual connotations—that recently caught the attention of psychologists Rebecca Burch and David Widman. In a series of studies published in the journal Evolutionary Behavioral Sciences bearing the cheeky title “The Point of Nipple Erection,” Burch and Widman reveal the world’s first-ever investigation into why, how, and what we read into erect nipples.
You’re probably thinking that’s a rather silly thing for scientists to study, but when you consider that men have difficulty not looking at nipples (seriously, they’ve done eye-tracking studies), it’s not so silly at all. The more astonishing thing, in fact, is that despite being part of our species’ Bauplan for hundreds of thousands of years (and hundreds of millions more before us) it was only five years ago that anyone bothered to look at whether erect nipples in humans affect how those humans are viewed and treated.
Previously, the authors explain, famed sex researchers William H. Masters and Virginia E. Johnson established that nipple erection is a part of “the human sexual response” (the title of their 1966 book). This titillating fact is true for both sexes, but with some notable differences. Let’s focus on women’s nipples for now. For human females, nipple erection is one of the first and most reliable external signs of sexual arousal, with papillae hardening and increasing in length by .5 - 1.0 cm and in base diameter .25 - .5 cm from their resting states. But once the female orgasm occurs, the nipples quickly return to their less piercing alter egos. (Please don’t use that as a failsafe method to tell if she’s “faking it” but I suppose it does have some practical applications.) Female nipple sensitivity also increases at puberty and fluctuates over the reproductive cycle, peaking at the ovulatory phase.
This uncontrollable bodily response of nipple erection is an honest signal precisely because it’s uncontrollable—one can’t pretend their way to tumescent tips or will them away. What they’re presumed to signal, of course, is where things get interesting, suspected Burch and Widman. And so, it’s here that they took the titular baton from Masters and Johnson. To determine if others’ nipple erection plays a causal role in our social judgments and decision-making about those people, the authors first needed to create an experimental paradigm with test stimuli that homed in on just that body part. “Photos of real women displaying nipple erection in real-world settings were collected from the Internet,” Burch and Widman explain. “All women were fully clothed and photographed while walking, standing, or sitting in public (candid photos).” The researchers narrowed these ostensibly endless options to the five most salient displays of nipple erection they could find, then created a matched control group in which those same erect nipples were concealed by photoshop. Thus, there were 5 photos of clothed women showing erect nipples, and 5 matched photos with those erect nipples edited out, suggestive of them, say, wearing a padded bra. Importantly, the women in the photos were anonymized by placing digital white boxes over their faces. This also served to control for any face-related confounds, such as age, attractiveness, or emotional expression, so that the experimenters could be confident that whatever results they might find were due entirely to the presence or absence of erect nipples.
The procedure—essentially the same across all five studies—was simple and straightforward. Participants sat down in front of the computer and were told they were going to see a slide show. Their job was to answer questions about the person in each photo, and about how that person made them feel. The 10 images appeared in a random order, with the only caveat being that each target slide was never shown directly before or after its unnippled analog.
In Burch and Widman’s first study, participants perceived the women with erect nipples as having more positive emotional states (relaxed, happy, confident, friendly). Remember, the images didn’t even show faces, so these differences were based on the visibility of the nipples alone. But here’s where men and women’s reactions to the images diverged. Male viewers not only saw the women with nipple erections as being sexually aroused, but they also reported that these women made them feel sexier and more positive. For female viewers, it was the opposite. Women didn’t see the women with erect nipples as feeling any hornier than the non-erect versions. However, they personally felt less sexy and as having more negative emotions in response to seeing other women with erect nipples than non-erect ones.
The authors interpreted these initial findings within an evolutionary framework. Human males are subject to what’s known as the “sexual overperception bias,” which is just what it sounds like. Given an ambiguous signal from an attractive woman—a smile, eye contact, a verbal pleasantry, and apparently, erect nipples—men tend to see this as the woman’s sexual interest in them. This biased reasoning is adaptive, theorists say, because it’s better for the male to act on the possibility of a reproductive opportunity than to not notice it at all or to assume the female’s disinterest. For women, by contrast, sexually receptive other women are seen (unconsciously) as competition or rivals within the reproductive domain.
In fact, Burch and Widman’s second study got at these sex differences even more directly. Here, they found that erect nipples were more likely to encourage male observers to come to the aid of the woman in the photo than those without such anatomical displays. This was especially the case when their assistance involved direct interaction with the woman in the photo (e.g., “You see her hitchhiking. Would you pick her up?” or “Would you share food if you are both hungry?”). “These men may perceive these women as sexually interested in them and more likely to behave altruistically toward them because of this sexual interest,” write the authors. The female participants, by contrast, were significantly less likely to help the women with nipple erections. “Women do not want these women [with erect nipples] in their social groups,” Burch and Widman explain, “even when these groups are for work or for other tasks.”
Oh, and that’s not all. A third study established that women with nipple erections were perceived—by both male and female participants—as less intelligent, less moral, and more promiscuous than their unnippled comparisons. They were viewed as more likely to have engaged in a range of sexual behaviors (one-night stands, threesomes, filming themselves having sex, etc.) and to have slept with more men. Female viewers even assumed that the women with nipple erections had lost their virginity at an earlier age.
Now, what I haven’t mentioned about all these findings is that the studies were done entirely with an American sample. And that, Burch and Widman realize, could be a huge factor in our reading into what these pointed messages entail. I mean, we Americans aren’t exactly known for being comfortable with nudity, which means that the only time we’re likely to encounter a woman’s bare breasts—with or without erect nipples—is in a highly sexualized setting, whether in the bedroom or in porn. When I was a little kid growing up in northern Virginia in the early 1980s, I caught my first eyeful of boobs on HBO, in that infamous pool scene from Fast Times at Ridgemont High. I’m gay, which probably explains why it did nothing for me. But it still felt scandalous; I remember my grandpa chuckling at my animated description when I reported this jaw-dropping sight to him the next morning. Given American prudery, then, perhaps we’ve come to associate nipple erection disproportionately with sexual arousal, when again, this automatic physiological response can be caused by a multiple of factors—not just erotic desire. “If nipple erection is rarely seen except for intimate or indoor contexts such as people disrobing in front of each other,” explain the authors, “[it] may be perceived as only existing in sexual or romantic contexts.”
And that’s where French nipples come in. Or at least, French participants. Not just them, in fact, but participants from other Western European countries as well, including Portugal, Germany, Ireland, Spain, the Netherlands, and the UK. The question was whether Western Europe’s more casual attitudes and frequent exposure to female breasts would be reflected in people’s inferences about what a woman is, erm, saying or not saying with her erect nipples. After all, unlike in the US, where a woman going topless in public is not only shocking, but expressly illegal in some states and deemed an “indecent act” (even many strip clubs require that dancers wear pasties to cover their areolas or face arrest), naked breasts are a far more common sight in Western Europe. Full frontal nudity on television hardly raises an eyebrow and clothing-optional beaches are commonplace. France alone has nearly 400 such beaches and over 200 nudist campsites.
With the human body being no big deal, the authors reasoned, perhaps Europeans simply have more experience with seeing other people’s erect nipples, realizing they’re caused by all sorts of things, not just sexual arousal. A topless woman emerging from a dip in a river in the Pyrenees might have erect nipples, but also other signs of being freezing, such as shivering and horripilation (raised hair and gooseflesh) on her other bare parts, such as her arms and legs. “At the very least,” posit the researchers, “nipple erection would be visible more easily and more often [in these societies], making it possible for viewers to see nipple erection in more varied contexts and therefore perceive it as having more than just sexual triggers.”
In a fourth study, therefore, Widman and Burch—this time joined by evolutionary psychologist T. Joel Wade from Bucknell University—conducted the same erect nipple experiment with Europeans. And guess what? Not only did the US results not replicate, but men judged the women without erect nipples as being “sexier” than those without. And in stark contrast with the US sample, European women were actually more likely to befriend the women with nipple erections, rather than shun them like their American counterparts.
I can’t leave without telling you about the results of Burch and Widman’s fifth study, which was on people’s perception of male nipple erection. Again, this automatic response is part of sexual response cycle, but for men it occurs at a different time. Nipple erection is not a reliable early sign of arousal—look further south for that—but it’s more likely once arousal has intensified. Over half of surveyed men reported that nipple play is sexually arousing to them. “Few men under 60 years of age ejaculate without an obvious turgidity, if not full erection, of the nipples,” wrote Masters and Johnson. It also takes longer for the effect to go away, which is to say that nipple erections remain long after male orgasm (sometimes hours).
So perhaps it’s not surprising that images of men with erect nipples led to some degree sexual objectification, just as it had with women. Women saw these men as more promiscuous, and both sexes judged them as less intelligent. Oddly, however, they were simultaneously seen as more moral than those without such prominent signals on their chests. Yet women still judged men with nipple erections as being more sexually manipulative than those without such bodily cues. On the one hand, explain the authors, women tend to see these men as hotter, but on the other hand as a threat. “These men may be perceived as [sexier], more interested in sex, and therefore more of a risk to the women’s choice in reproductive decisions . . . These men may be more attractive but also instigate a defensiveness on the part of the women.”
As for whether anyone—male or female—is more inclined to, say, pick up a male hitchhiker with erect nipples or share a meal with him, not so much. It didn’t seem to matter one (tit)bit.
Like what you read? Toss a tip in the jar—any amount that makes sense for you—so I can keep overthinking things on your behalf.