Brain Rules: 12 Principles for Surviving and Thriving at Work, Home, and School by John Medina Page A

to another. It is time-consuming. And it is sequential. That’s why we can’t multitask. That’s why people find themselves losing track of previous progress and needing to “start over,” perhaps muttering things like “Now where was I?” each time they switch tasks. The best you can say is that people who appear to be good at multitasking actually have good working memories, capable of paying attention to several inputs one at a time.
    Here’s why this matters: Studies show that a person who is interrupted takes 50 percent longer to accomplish a task. Not only that, he or she makes up to 50 percent more errors.
    Some people, particularly younger people, are more adept at task-switching. If a person is familiar with the tasks, the completion time and errors are much less than if the tasks are unfamiliar. Still, taking your sequential brain into a multitasking environment can be like trying to put your right foot into your left shoe.
    A good example is driving while talking on a cell phone. Until researchers started measuring the effects of cell-phone distractions under controlled conditions, nobody had any idea how profoundly they can impair a driver. It’s like driving drunk. Recall that large fractions of a second are consumed every time the brain switches tasks. Cell-phone talkers are a half-second slower to hit the brakes in emergencies, slower to return to normal speed after an emergency, and more wild in their “following distance” behind the vehicle in front of them. In a half-second, a driver going 70 mph travels 51 feet. Given that 80 percent of crashes happen within three seconds of some kind of driver distraction, increasing your amount of task-switching increases your risk of an accident. More than 50 percent of the visual cues spotted by attentive drivers are missed by cell-phone talkers. Not surprisingly, they get in more wrecks than anyone except very drunk drivers.
    It isn’t just talking on a cell phone. It’s putting on makeup, eating, rubber-necking at an accident. One study showed that simply reaching for an object while driving a car multiplies the risk of a crash or near-crash by nine times. Given what we know about the attention capacity of the human brain, these data are not surprising.
    4) The brain needs a break
    Our need for timed interruptions reminds me of a film called Mondo Cane , which holds the distinction of being the worst movie my parents reported ever seeing. Their sole reason for hating this movie was one disturbing scene: farmers force-feeding geese to make pâté de foie gras . Using fairly vigorous strokes with a pole, farmers literally stuffed food down the throats of these poor animals. When a goose wanted to regurgitate, a brass ring was fastened around its throat, trapping the food inside the digestive tract. Jammed over and over again, such nutrient oversupply eventually created a stuffed liver, pleasing to chefs around the world. Of course, it did nothing for the nourishment of the geese, sacrificed in the name of expediency.
    My mother would often relate this story to me when she talked about being a good or bad teacher. “Most teachers overstuff their students,” she would exclaim, “like those farmers in that awful movie!” When I went to college, I soon discovered what she meant. And now that I am a professor who has worked closely with the business community, I can see the habit close up. The most common communication mistakes? Relating too much information, with not enough time devoted to connecting the dots. Lots of force-feeding, very little digestion. This does nothing for the nourishment of the listeners, whose learning is often sacrificed in the name of expediency.
    At one level, this is understandable. Most experts are so familiar with their topic that they forget what it is like to be a novice. Even if they remember, experts can become bored with having to repeat the fundamentals over and over again. In college, I found that a lot of my professors,