Brainwork. David A. SousaЧитать онлайн книгу.
go any further, we need to define what the term multitasking means in this context. The original definition of multitasking came from the computer industry and referred to a microprocessor’s ability to carry out more than one task at a time. Obviously, humans can multitask in that they can simultaneously walk and talk, or ride a bicycle while pondering the beauty of nature, or knit while watching television. We are able to do these tasks concurrently because different parts of the brain are in command of each. Walking, riding a bicycle, and knitting are learned motor skills that are controlled primarily by a structure at the rear base of the brain called the cerebellum (see fig. 2.1). Talking, pondering, and watching television are cognitive operations, which we know are the main responsibility of the prefrontal cortex. As long as we perform tasks that call on two brain regions with separate responsibilities, we are able to carry them out successfully. But when we call on the same part of the brain to carry out two or more functions simultaneously, problems arise.
Figure 2.1: The prefrontal cortex deals with cognitive processing. The cerebellum controls motor movements, balance, and equilibrium.
Let’s demonstrate this notion with a simple but amusing motor skills activity. Sit in a chair, lift your right leg, and move it in clockwise circles for several seconds. Stop. Place your right foot back on the floor. Now extend your right arm and your right index finger. Use this finger to draw the number 8 continuously for several seconds. Stop. Now lift your right leg and move it in clockwise circles while at the same time drawing the number 8 with your right hand. How did you do? Did you lose control of either your leg or your hand movements?
What happened here? You were able to perform each of the movements separately. However, as soon as you tried to do them together, you were calling on the cerebellum to control two unrelated motor tasks simultaneously—a feat it cannot do. The neural signals got scrambled, and you lost control. Similar results will occur when the prefrontal cortex encounters the same predicament. Ever try to talk on the phone and write an email at the same time? Those cognitive activities are almost impossible to do together. For the purposes of this discussion, multitasking refers to calling on the same brain region to carry out more than one task simultaneously.
Survival Requires Focus
Remember, the brain’s main task is to keep its owner alive. Survival requires the ability to focus intently on incoming signals that could pose a threat to the individual. Those ancestors of ours who were unable to do so most likely ended up as some predator’s lunch; their genes never entered the gene pool. On the other hand, the individuals who were able to concentrate on a threat and find ways to avoid or defeat it were more apt to live long enough to find a mate and transmit that focusing ability to their offspring—and a few hundred millennia later, to us.
Torkel Klingberg, a cognitive neuroscientist at the Karolinska Institute in Sweden, has conducted experiments with brain scans that indicate that a certain region of the brain (known as the globus pallidus) is highly active when individuals are fending off distractions.1 Think of this area as a nightclub bouncer, preventing irrelevant items from getting into the club called working memory. This makes sense. Focus equals survival. When a car is speeding toward you in the wrong lane and a head-on collision is imminent, you do not want your brain’s attention systems shifting suddenly to admiring the colorful flowers on the roadside trees or wondering whether the car needs a new set of tires.
In 2009, when Captain Chesley Sullenberger was piloting his disabled jet over the Hudson River with 155 passengers and crew on board, he knew that focus was his only hope. He didn’t even pray. “I imagine somebody in back was taking care of that for me,” he told Katie Couric of CBS News. “My focus was so intensely on landing, I thought of nothing else.” In the three minutes he had from the time the plane started its unrelenting descent until it hit water, Sullenberger screened out all external input and relied on his forty years of flying experience to guide the sixty-ton aircraft. After a bumpy landing on the water’s surface, he said to his copilot, “Well, that wasn’t as bad as I thought.”2 Thanks to his focusing ability, not one life was lost.
Safety experts advise against using a cell phone while driving because they want drivers to avoid distractions during cognitive activities. Talking on a cell phone requires significant cognitive resources. About 70 percent of a face-to-face conversation involves nonverbal communication, such as facial expressions, body gestures, posture, and degree of eye contact, all of which carry meaning. In the absence of these nonverbal cues—such as during a phone call—the brain has to work harder by analyzing the caller’s voice for tone, pitch, and pacing to determine the true meaning and intent of the caller’s words. This is not easy because even the best technology does not faithfully transmit all the characteristics of a person’s voice. Such diversion of attention resources—about 37 percent, according to the fMRI scans—significantly reduces the driver’s response time and ability to make quick decisions when the car in front suddenly brakes or another car unexpectedly changes lanes. Research studies conducted by David Strayer and his colleagues at the University of Utah and neuroscientist Marcel Just at Carnegie Mellon University have shown that the cognitive impairments that occur when using a cell phone while driving are as serious as those associated with driving while drunk.3 That’s scary. If you are thinking that hands-free or voice-activated cell phones are safer, you are mistaken. These studies showed that they made little difference in the driver’s level of distraction.
Does talking to someone in the car involve the same amount of distraction? No. Strayer’s research found that although talking with a passenger involves some diversion of attention, it is far less than the distraction of a phone conversation. In the car, you can hear all the characteristics of the passenger’s voice, and your eyes may catch direct or peripheral views of the speaker, helping you assess those important nonverbal signals. In short, it is a lot easier for your brain to determine the meaning and intent of the passenger’s words in the car than those of the caller on the phone. Furthermore, the passenger is an extra set of eyes to alert you to road hazards.
What about texting and driving? Well, let’s see. I am going to be driving a vehicle, a task that requires the full attention of my eyes and extensive coordination of my hands. Oh, and at the same time, I am going to be texting a message, a task that requires considerable attention from my eyes and intricate coordination of my fingers. Is there a problem with that? This combination is not only dangerous, it is insane!
The Costs of Tasking
If the man in the airport lounge is not multitasking, then what is he doing? When the brain has to attend to multiple items in working memory, one option is to shift its focus back and forth between two items at astonishing speeds. This is called alternate tasking. Or, the brain can shift its focus among more than two items, a process called sequential tasking. Figure 2.2 illustrates the two options.
Figure 2.2: The left diagram shows alternate tasking as the brain shifts its attention from A to B and back to A. The right diagram shows sequential tasking, with attention shifting from X to Y to Z and back to X.
The brain of our airport executive is probably using both methods. He is doing alternate tasking when, for example, his attention moves from the newspaper to the digital assistant and then to the paper again. If he were to get a phone call about a change in a meeting date, he would likely engage in sequential tasking. He would focus first on the caller’s message (X in fig. 2.2), turn to the digital assistant to send a text message to his office advising of the new date (Y), and then focus on his laptop to alter the dates in his slide presentation (Z). Then he could tell the caller that he made the necessary changes (back to X).
At this point, you might be thinking, “So what? Does it make any difference that multitasking is really alternate or sequential