Many adults and students today think of themselves as excellent multitaskers--switching from task to task or from task to play in a nanosecond. Yet the pings and tweets their devices emit interrupt them in ways that are more problematic than they think. One of the powerful myths in the culture today is that multitasking is efficient for work or for learning. Research, however, tells a different story. Among adults who spend time multitasking at work or home, more and more people report having difficulty concentrating on a single complex task for an extended period of time. More people, in fact, wonder if their memories are eroding. And more people report having difficulty actually reading a book or a long article online. The costs of media multitasking are considerable. They include a decrease in executive function (such as the ability to prioritize tasks and figure out what information is most valuable), a decrease in the ability to focus on complex tasks, a decrease in long-term memory, and an increase in stress. When people jump from task to task, quickly scan for information, and shift constantly between work and play, they neither learn things in depth nor retain long-term memories about what they have learned, at least not in a way that they do when they single task. And when they learn while multitasking, they are less able to work creatively with what they know, to problem solve "outside the box." Understanding the neurological and psychological bases for these assertions, which are backed by an already substantial and ever-increasing body of research, should help one to take appropriate action in the school and home setting. (Contains 1 note.)