When I call out my students for being distracted in class, the most common response is, "I'm multitasking!" I generally point out that multitasking is a myth. This article from Maria Konikova at The New Yorker gives me the science to back that up.
Strayer believes that there is a tiny but persistent subset of the population—about two per cent—whose performance does not deteriorate, and can even improve, when multiple demands are placed on their attention. The supertaskers are true outliers. According to Strayer, multitasking isn’t part of a normal distribution akin to birth weight, where even the lightest and heaviest babies fall within a relatively tight range around an average size. Instead, it is more like I.Q.: most people cluster in an average range, but there is a long tail where only a tiny fraction—single digits among thousands—will ever find themselves.
I taught about 80 students this year, so according to this study 1.6 of my students are actually capable of multitasking.