In a university library, a student is writing an essay on his laptop. But that’s not all. He’s also reading instant messages online, listening to his music with headphones, and checking text messages on his cell phone. In today’s world, people use a wide variety of electronic media to multitask, doing several things at the same time. Neuroscientists are studying the brain to see what happens during multitasking and to see if multitasking affects the quality of what we do. In a multitasking study conducted by French scientists Eienne Koechlin and Sylvain Charron, people were given one task requiring concentration. Brain images showed that both the left and right prefrontal cortex ( 前额叶皮质 ) were active as people worked. However, when the person is given a second task to do at the same time, the left prefrontal cortex look on task, and the right look the other. When doing two tasks, MRI ( 磁共振成像 ) images showed that the brain was rapidly switching between the first and the second task. The brain was not working on both tasks at the same time. It is concentrating on one task and then switching to the other. In order to switch attention from one task to another, the brain must use its working memory. This is the brain’s ability to temporarily hold information while it does something else. When you multitask, the first task is stored in your working memory. Then your brain goes to the second task but when it returns to the first task, it must restart it , using working memory. Although we think we are getting more done by multitasking, evidence shows that we do not. Researchers have found that people take longer to complete tasks and make more mistakes. When the French researchers expanded their experiment to include three tasks, surprisingly, the brain seemed to completely drop on task and only focus on two tasks. The French team concluded that the brain could not focus on more than two tasks at a time. Therefore, for a task that requires your concentration, it’s better to just focus on that one task until you are done.