A new study indicates that binge watching television, when combined with very little exercise, degenerates your mental capacities at an astonishing rate, even in very young people. So, in case you were wondering why the Netflix and chill generation seems like a teeming horde of slack-jawed mouth breathers, now you know:

Researchers at the Northern California Institute for Research and Education analyzed data from a 25-year-long study of more than 3,200 18-to 30-year-olds. Those who reported watching the most TV (usually more than three hours a day) and doing the least physical activity (usually less than two and half hours a week) had the worst decline in cognitive functioning over the course of the study, even before the participants were middle-aged.

“[This inactivity] affects cognitive functioning even younger than we realized,” says one of the researchers, Tina Hoang. She and her co-authors, including Dr. Kristine Yaffe, professor at University of California, San Francisco, School of Medicine, found that people who watched a lot of TV and had low levels of physical activity had weaker working memories, slower processing speed and worse executive function (ability to plan and complete tasks) than their peers, even adjusting for education.

So perhaps we should all hit the books instead. Or, you know, hit the gym. Or just go outside and run around a little. Anything. I’ve been doing my own research for most of my life, and I can tell you that people in my generation and younger are, generally speaking, idiots. Television probably has something to do with it. But parenting enters into that. Parents these days don’t want to parent. So they stick their kids in front of TV more than ever. And in the insightful, though creepy, words of the Cable Guy: “Somebody has to kill the babysitter.”