Answered Dec 14, 2019
Note that this question appears to have changed since previous answers, and now specifies “during lectures”.
One time, I noticed a significant change in the way that computers were being used.
In first year, I sat near the back, and could see many of the other students’ screens.
Some were taking notes or scrolling though the PDF of the lecture (which was often available for download ahead of time).
However, a good percentage of students were scrolling through FaceBook, playing games, shopping, and doing other irrelevant web surfing. Some also seemed to be writing email.
That second category of computer use was at least more subtle than the blatant playing with phones.
In a certain second year class (which had first year prerequisites that had to have been passed), I also sat in the back, and could see the laptop screens.
At that point, every screen had the PDF of the slides for the lecture.
Also, nobody was playing with their phone.
Honestly, I don’t believe that, all of the people who were distracting themselves before, had magically improved to be more focused and serious.
Rather, my guess is that, the change was a matter of filtering. In which many of the self-distracting people simply weren’t there anymore.