I have written about this before, and it is included in my open letter to students every year. My experience has been that students with laptops in the classroom are generally unable to resist the temptation, now and then, to check the news, check email, check Facebook, play games, etc. Quite frankly if students want to do this rather than pay attention to my pearls of wisdom, I am a bit insulted, but after all it is their nickel and if that is what they want to do, okay.
But the problem is that students on laptops create negative externalities -- they distract the students around them, especially when they use the laptops for something other than taking notes.
When I first discovered this problem, I told the students, "If you want to use a laptop, you must sit in the back row." My theory was that this would create fewer distractions for other other students. It didn't work very well, though, because they'd be tap-tapping at totally inappropriate moments or, worse, they would be comparing messages and photos and game results with others in the back row.
So finally, about 8 or so years ago, I banned laptops from the classroom. Now [ht Ms Eclectic] there has been a study supporting my position. I have no idea how solid the methodology is, but given my own confirmation bias, I'm sure the results are correct 8-):
"[Y]ou might not be multitasking but if you have a clear view of someone else who is multitasking, your performance is still going to be impaired."
The students in the first experiment who were asked to multitask averaged 11 per cent lower on their quiz. The students in the second experiment who were surrounded by laptops scored 17 per cent lower. ...
Not aware of distraction
"At the end we gave a survey to all the students and what we found was that these peers who were seated around multitaskers had no idea they were being distracted, they didn't think the laptops were causing a distraction but based on the scores of their final test, they actually were," ...