With the Casual Sex Project, Vrangalova is trying to build a user base of stories that she hopes will, one day, provide the raw data for academic study. For now, she is listening: letting people come to the site, answer questions, leave replies. Ritch Savin-Williams, who taught Vrangalova at Cornell, told me that he was especially impressed by Vrangalova’s willingness “to challenge traditional concepts and research designs with objective approaches that allow individuals to give honest, thoughtful responses.”

The result is what is perhaps the largest-ever repository of information about casual-sex habits in the world—not that it has many competitors. The people who share stories range from teens to retirees (Vrangalova’s oldest participants are in their seventies), and include city dwellers and suburbanites, graduate-level-educated professionals (about a quarter of the sample) and people who never finished high school (another quarter). The majority of participants aren’t particularly religious, although a little under a third do identify as at least “somewhat” religious. Most are white, though there are also blacks, Latinos, and other racial and ethnic groups. Initially, contributions were about sixty-per-cent female, but now they’re seventy-per-cent male. (This is in line with norms; men are “supposed” to brag more about sexual exploits than women.) Anyone can submit a story, along with personal details that reflect his or her demographics, emotions, personality traits, social attitudes, and behavioral patterns, such as alcohol intake. The setup for data collection is standardized, with drop-down menus and rating scales.

Still, the site is far from clinical. The home page is a colorful mosaic of squares, color-coded according to the category of sexual experience (blue: “one-night stand”; purple: “group sex”; gray: the mysterious-sounding “first of many”; and so on). Pull quotes are highlighted for each category (“Ladies if you haven’t had a hot, young Latino stud you should go get one!”). Many responses seem to boast, provoke, or exaggerate for rhetorical purposes. Reading it, I felt less a part of a research project than a member of a society devoted to titillation.

Vrangalova is the first to admit that the Casual Sex Project is not what you would call an objective, scientific approach to data collection. There is no random assignment, no controls, no experimental conditions; the data is not representative of the general population. The participants are self-selecting, which inevitably colors the results: if you’re taking the time to write, you are more likely to write about positive experiences. You are also more likely to have the sort of personality that comes with wanting to share details of your flings with the public. There is another problem with the Casual Sex Project that is endemic in much social-science research: absent external behavioral validation, how do we know that respondents are reporting the truth, rather than what they want us to hear or think we want them to say?

And yet, for all these flaws, the Casual Sex Project provides a fascinating window into the sexual habits of a particular swath of the population. It may not be enough to draw new conclusions, but it can lend nuance to assumptions, expanding, for instance, ideas about who engages in casual sex or how it makes them feel. As I browsed through the entries after my meeting with Vrangalova, I came upon the words of a man who learned something new about his own sexuality during a casual encounter in his seventies: “before this I always said no one can get me of on a bj alone, I was taught better,” he writes. As a reflection of the age and demographic groups represented, the Casual Sex Project undermines the popular narrative that casual sex is the product of changing mores among the young alone. If that were the case, we would expect there to be a reluctance to engage in casual sex among the older generations, which grew up in the pre-“hookup culture” era. Such reluctance is not evident.

The reminder that people of all ages engage in casual sex might lead us to imagine three possible narratives. First, that perhaps what we see as the rise of a culture of hooking up isn’t actually new. When norms related to dating and free love shifted, in the sixties, they never fully shifted back. Seventy-year-olds are engaging in casual encounters because that attitude is part of their culture, too.

There’s another, nearly opposite explanation: casual sex isn’t the norm now, and wasn’t before. There are simply always individuals, in any generation, who seek sexual satisfaction in nontraditional confines.

And then there’s the third option, the one that is most consistent with the narrative that our culture of casual sex begins with college hookups: that people are casually hooking up for different reasons. Some young people have casual sex because they feel they can’t afford not to, or because they are surrounded by a culture that says they should want to. (Vrangalova’s preliminary analysis of the data on her site suggests that alcohol is much more likely to be involved in the casual-sex experiences of the young than the old.) And the old—well, the old no longer care what society thinks. For some, this sense of ease might come in their thirties; for others, their forties or fifties; for others, never, or not entirely.

This last theory relates to another of Vrangalova’s findings—one that, she confesses, came as a surprise when she first encountered it. Not all of the casual-sex experiences recorded on the site were positive, even among what is surely a heavily biased sample. Women and younger participants are especially likely to report feelings of shame. (“I was on top of him at one point and he can’t have forced me to so I must have consented . . . I’m not sure,” an eighteen-year-old writes, reporting that the hookup was unsatisfying, and describing feeling “stressed, anxious, guilt and disgust” the day after.) There is an entire thread tagged “no orgasm,” which includes other occasionally disturbing and emotional tales. “My view has gotten a lot more balanced over time,” Vrangalova said. “I come from a very sex-positive perspective, surrounded by people who really benefitted from sexual exploration and experiences, for the most part. By studying it, I’ve learned to see both sides of the coin.”

Part of the negativity, to be sure, does originate in legitimate causes: casual sex increases the risk of pregnancy, disease, and, more often than in a committed relationship, physical coercion. But many negative casual-sex experiences come instead from a sense of social convention. “We’ve seen that both genders felt they were discriminated against because of sex,” Vrangalova told me. Men often feel judged by other men if they don’t have casual sex, and social expectations can detract from the experiences they do have, while women feel judged for engaging in casual experiences, rendering those they pursue less pleasurable.

Perhaps this should come as no surprise: the very fact that Vrangalova and others are seeking explanations for casual-sex behaviors suggests that our society views it as worthy of note—something aberrant, rather than ordinary. No one writes about why people feel the need to drink water or go to the bathroom, why eating dinner with friends is “a thing” or study groups are “on the rise.”

It is that sense of shame, ultimately, that Vrangalova hopes her project may help to address. As one respondent to a survey Vrangalova sent to users put it, “This has helped me feel okay about myself for wanting casual sex, and not feel ashamed or that what I do is wrong.” The psychologist James Pennebaker has found over several decades of work that writing about emotional experiences can act as an effective form of therapy, in a way that talking about those experiences may not. (I’m less convinced that there are benefits for those who use the site as a way to boast about their own experiences.) “Often there’s no outlet for that unless you’re starting your own blog,” Vrangalova points out. “I wanted to offer a space for people to share.”

That may well end up the Casual Sex Project’s real contribution: not to tell us something we didn’t already know, or at least suspect, but to make such nonjudgmental, intimate conversations possible. The dirty little secret of casual sex today is not that we’re having it but that we’re not sharing our experiences of it in the best way.