This article originally appeared on Time.com.
Contrary to popular belief, today’s kids are not growing up too fast. According to a new study published in the journal Child Development, they’re growing up slower than they used to.
The researchers analyzed survey responses from 8.3 million adolescents, ages 13 to 19, from across the country over the last 40 years (1976 to 2016). They found that today’s youths, compared to those in previous decades, are less likely to engage in adult activities, including drinking alcohol, dating, having sex, going out without their parents, driving a car and working a job.
Today, the researchers say, 18-year-olds act more like 15-year-olds from previous decades. That was true across all demographic groups in the study.
The new findings are consistent with other recent research, and they tell a complicated story of teens today. “Some people have written that alcohol use and sexuality are down, so that must mean that teens are more virtuous than they used to be,” says lead author Jean Twenge, professor of psychology at San Diego State University. “Others wrote that they’re less likely to have jobs, so they must be lazy or immature.”
“If you look at the big picture, it’s not that they’re doing more good things or more bad things overall,” says Twenge. “It’s just that they’re less likely to do all kinds of things that adults do, and there is definitely a trade-off there.”
One downside to slower development is that teens may be unprepared for living independently when they go off to college, get their first job or set out on their own, Twenge says. But there are also plenty of benefits, especially for teens’ health. “When kids don’t grow up before they’re ready, they’re protected from things like alcohol and sex,” says Twenge.
The study’s findings may help explain why the teen birth rate rate is lower than ever, Twenge says, and why teenagers get in fewer car accidents than they used to. “Teens are safer and healthier than they’ve ever been,” she says, “and that’s obviously a very good thing.” (The latter statistic comes from research Twenge did for her new book, iGen: Why Today’s Super-Connected Kids Are Growing Up Less Rebellious, More Tolerant, Less Happy—and Completely Unprepared for Adulthood.)
The new study did not investigate why maturity has slowed among teenagers, but the researchers have a few guesses. Twenge and her co-author cite the evolutionary “life-history theory,” which states that human development will be slower when families are smaller, people live longer, children are safe and healthy and education takes longer to complete. “That’s a pretty good description of our current culture,” says Twenge.
It’s also possible that the use of smartphones and Internet access has played a role in accelerating these patterns over the last five or so years. Because they allow kids to communicate with friends without leaving their homes, she says, they have less opportunity to engage in adult activities. “But it’s clear that technology is not the only cause of these trends,” she adds, “given that they began long before smartphones or the Internet were mainstream.”