I've done a number of posts on the evils of multitasking (for example here and here, or enter multitasking in the search box in the left column of this blog), and thus was struck by a number of salient points in an article by Perri Klass. Here are some clips:
...A recent and much-discussed study showed decreased productivity in adults who were multitasking...you don’t really multitask, you just think you do; the brain can’t process two high-level cognitive things. What you are actually doing...is oscillating between the two...So are teenagers any better at oscillating?...It may be that multitasking is more of a problem for us old brains...parents are digital immigrants...children are digital natives...they really have come of age with these technologies.One possibility is that performing a task while allowing distractions lengthens the amount of time that can be spent on the task, more than compensating for a decrease in efficiency.
The literature looking at media and its impact on attentional skills is just in its infancy...We don’t really know what they pay attention to, what they don’t. We don’t know how it impacts their school performance, whether it impacts their school performance.