Jeremy Littau is an assistant professor of journalism and communication at Lehigh University in Pennsylvania who focuses on media and technology. The topic became intensely personal when he noticed something interesting about the students in his classes.

Those who brought laptops with them, purportedly for note-taking, seemed to be performing less well than students who did not. And not only were they distracted; so were their nearby classmates.

"There's a halo effect, where people are being distracted by what's on the screen," says Littau. "The conspiracy theorist in me assumed they were on Facebook."

Apparently, some were. Or on Twitter or YouTube or eBay, or all three at the same time. One architecture student turned out to be designing a building while Littau was conducting lectures.

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When he started surreptitiously tracking the performance of the laptop users, Littau found out something else about them: they were getting lower grades.

Now, along with a growing number of other US academics - and backed by new neurological research suggesting that technological distractions are taking a significant toll on learning - he has taken the dramatic step of banning laptops from his classes.

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"There are some times in life when you have to unplug," he says. "We fall in love with the idea of technology and don't always think through what students are learning from it.

"Technology tools are just that: they are tools. Even when they become something that's just there to waste time, that's fine. But if it's my time or your classmates' time, that's different."

He adds: "We've had enough experience with the internet that it's now time to sit back and look at what we're getting from it."

The backlash against technology comes after universities have spent fortunes wiring their campuses for access to the internet. And it is happening not only at places such as Lehigh, but also at technological institutions such as the Massachusetts Institute of Technology and elite law schools including those of Harvard University and the University of Chicago.

"Now is the time of repentance," jokes Sherry Turkle, professor of the social studies of science and technology at MIT, founder of the MIT Initiative on Technology and Self, and a clinical psychologist.

"We have to force ourselves to shift our perspective on this and see our relationship to this technology, and our work at controlling it, as being in its infancy. And what we're learning is that having a red light on a BlackBerry blinking at you is a kind of technological siren that people are drawn to."

The author, most recently, of Alone Together: Why We Expect More from Technology and Less from Each Other (2011), adds: "We're very vulnerable. I don't like to use the word 'addicted' because 'addicted' makes it seem that you have to get off it. You're not going to get off the internet or your (mobile) phone. These are the technologies of our lives.

"But what professors are learning to say is: 'You know what? In this class we're here to be with each other. We're here to be a community. Let's make the most of it.'"

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Turkle says that the movement to reduce or halt online access during lectures is gathering "tremendous" momentum.

"Universities had great technological enthusiasm. But as I'm travelling around now, I'm feeling the backlash," she adds.

Chicago Law School has blocked wireless internet access in some classrooms. At least one Harvard academic - Jonathan Zittrain, ironically a specialist in internet law - has banned laptops and mobile devices from one of his classes.

Other universities have variously declared internet-free zones, week-long technology "retreats", or 15-minute periods a day to disconnect.

As a one-week experiment last year, Harrisburg University of Science and Technology in Pennsylvania blocked access over its wireless network to social-media sites - not only for students, but also for academics and other staff.

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Although many tech-savvy students at the institution complained bitterly - some wore T-shirts printed with the words, "We all have smartphones, dumbass" - a quarter of them later reported that they were better able to concentrate in class, found lectures more interesting and spent more time doing homework. Some even said that they ate better and exercised more.

Multitasking or minds wandering?

Their experience is borne out by recent research at Stanford University by Clifford Nass, Thomas M. Storke professor of communication.

Nass, who lives in a student dormitory as a resident Fellow, noticed that his students were constantly online while talking, listening or doing other things.

"My first thought was: 'Damn, these kids can multitask,'" says Nass, the founder of Stanford's Communication between Humans and Interactive Media Lab and the author of The Man Who Lied to His Laptop: What Machines Teach Us About Human Relationships (2010).

"It seemed as though they could actually do two things at once. What do these kids know that I don't? It drove me crazy. That's what inspired my research."

But he found that "they're not amazing. They can't really do it." His research shows that the students' memories were disorganised; they fixated on irrelevant data, could not follow specific directions that required paying attention and wrote poorly.

University lecturers have come to see this every day, Nass says.

"We've reached a period where attention is no longer valued. There's been a cultural change where we've forgotten about the idea of paying attention," he says. "And people have started to resent that."

Still, it is hard to wean this generation off the internet, according to Jennifer MacGregor. She tried to do it with a recent class of first-year students at St Lawrence University in New York State in a seminar about internet usage and identity. MacGregor, a visiting assistant professor of psychology who is working on a book called I Text, Therefore I Am, required students to refrain from using their mobile phones, internet and email for two weeks.

"The number one emotion that came up was anxiety," she says. "They were panicked. It was almost as though (they thought), 'I no longer exist'."

But she adds that the students also reported - in the handwritten journals they were required to keep - that they spent much more time in face-to-face conversation and were less distracted.

For her part, MacGregor says, deprived of email, she found herself "walking up and down the halls chatting with colleagues. And I liked it so much that when I went back online, I kept doing it."

All of these experts counsel not switching off the internet altogether, but teaching students how to use it - and, at times, ignore it.

"We've made it very confusing for our students," Turkle argues. "We have put the whole course online. We've videotaped it so that they can stay home and watch it in their rooms. We've put everything online so they have a reason to open the laptop. We've done this for them thinking it was progress. It confuses them when we now say: 'Don't open your laptop.'"

Nass says that expectations have to change. Instead of pulling wireless networks out of classrooms, he suggests, "couldn't you instead say: 'Look, in my class I consider it an insult for you to be online, because that's how we do things around here'?"

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He adds: "It's only disrespectful if we treat it as disrespectful. The fact is that we make it easy and allow people to get away with it. But if universities allow or encourage it, or don't actively discourage it, then you're creating a situation that does not just have short-term but also long-term effects."