So here’s the takeaway for parents of Generation M: Stop fretting about how much they’re on Facebook. Don’t harass them about how much they play video games. The digital native boosters are right that this is the social and emotional world in which young people live. Just make sure when they’re doing schoolwork, the cellphones are silent, the video screens are dark, and that every last window is closed but one.

Rideout, director of the Kaiser study on kids and media use, sees an upside for parents in the new focus on multitasking while learning. “The good thing about this phenomenon is that it’s a relatively discrete behavior that parents actually can do something about,” she says. “It would be hard to enforce a total ban on media multitasking, but parents can draw a line when it comes to homework and studying—telling their kids, ‘This is a time when you will concentrate on just one thing.’ ”

Follow-up studies performed years later found that the kids who were better able to delay gratification not only achieved higher grades and test scores but were also more likely to succeed in school and their careers.

Meyer, of the University of Michigan, worries that the problem goes beyond poor grades. “There’s a definite possibility that we are raising a generation that is learning more shallowly than young people in the past,” he says. “The depth of their processing of information is considerably less, because of all the distractions available to them as they learn.”

Finally, researchers are beginning to demonstrate that media multitasking while learning is negatively associated with students’ grades. In Rosen’s study, students who used Facebook during the 15-minute observation period had lower grade-point averages than those who didn’t go on the site. And two recent studies by Reynol Junco, a faculty associate at Harvard’s Berkman Center for Internet & Society, found that texting and using Facebook—in class and while doing homework—were negatively correlated with college students’ GPAs. “Engaging in Facebook use or texting while trying to complete schoolwork may tax students’ capacity for cognitive processing and preclude deeper learning,” write Junco and a co-author. (Of course, it’s also plausible that the texting and Facebooking students are those with less willpower or motivation, and thus likely to have lower GPAs even aside from their use of technology.)

Brain scans taken during Poldrack’s experiment revealed that different regions of the brain were active under the two conditions, indicating that the brain engages in a different form of memory when forced to pay attention to two streams of information at once. The results suggest, the scientists wrote, that “even if distraction does not decrease the overall level of learning, it can result in the acquisition of knowledge that can be applied less flexibly in new situations.”

They may like to do it, they may even be addicted to it, but there’s no getting around the fact that it’s far better to focus on one task from start to finish.”

An example would be folding laundry and listening to the weather report on the radio. That’s fine. But listening to a lecture while texting, or doing homework and being on Facebook—each of these tasks is very demanding, and each of them uses the same area of the brain, the prefrontal cortex.”

Other professors have taken a more surreptitious approach, installing electronic spyware or planting human observers to record whether students are taking notes on their laptops or using them for other, unauthorized purposes.

the new marshmallow test of self-discipline—is the ability to resist a blinking inbox or a buzzing phone.

it wasn’t long before their attention drifted: Students’ “on-task behavior” started declining around the two-minute mark as they began responding to arriving texts or checking their Facebook feeds.

A checklist on the form included: reading a book, writing on paper, typing on the computer—and also using email, looking at Facebook, engaging in instant messaging, texting, talking on the phone, watching television, listening to music, surfing the Web.