People may think of millennials as being one right swipe away from a quick hookup, but a new study suggests many 20-somethings are actually having less sex than their parents did back in the day.

“The misperception that millennials have a hook-up culture may be driven by the most promiscuous members of the generation, who are now able to advertise their exploits through social media,” said lead study author Jean Twenge, a psychology researcher at San Diego State University in California.

“But the culture of dating apps leaves out a large segment of the population,” Twenge added by email.

In reality, millennials born in the 1990s are more than twice as likely to be sexually inactive as young GenX’ers born in the late 1960s, Twenge and colleagues report in the Archives of Sexual Behavior.

Fifteen percent of young adults aged 20 to 24 reported having no sex since turning 18, compared with just 6 percent of the previous generation at that age, the study found.

Previous research has also found that millennials – born from the 1980s to 2000 – have fewer sexual partners than Generation X’ers or baby boomers, Twenge said.

To look at generational shifts in sexual activity, researchers examined survey data from a nationally representative sample of more than 26,000 adults.

One limitation of the study is that the survey didn’t ask about specific sexual activities, making it impossible to determine how respondents interpreted questions about whether they were sexually active, the authors note.

Still, the findings suggest that millennials may be experiencing a unique set of circumstances that, combined, may make them less likely to have sex in their 20s, the authors conclude.

For one thing, young adults are living longer with their parents and delaying marriage, which may delay sexual activity, the researchers note.

Oddly, the rise of hookup culture may dissuade sexual activity as teens and young adults shy away from committed relationships.

The mismatch between how adults perceive the millennial hookup culture and the reality of what 20-somethings are actually doing in bed speaks to a larger story about how older generations tend to view the kids that come after them, said Joshua Grubbs, a researcher at Bowling Green State University in Ohio who wasn’t involved in the study.

“Middle-aged and younger adults have complained about how disrespectful younger generations were, how risque they were, how immoral they were, how lazy they were or how unwise they were – this is sort of the natural order of things,” Grubbs said by email.