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It is also what makes multitasking a poor long-term strategy for learning. Other studies, such as those performed by psychologist René Marois of Vanderbilt University, have used fMRI to demonstrate the brain’s response to handling multiple tasks. Marois found evidence of a “response selection bottleneck” that occurs when the brain is forced to respond to several stimuli at once. As a result, task-switching leads to time lost as the brain determines which task to perform. Psychologist David Meyer at the University of Michigan believes that rather than a bottleneck in the brain, a process of “adaptive executive control” takes place, which “schedules task processes appropriately to obey instructions about their relative priorities and serial order,” as he described to the New Scientist
William James, the great psychologist, wrote at length about the varieties of human attention. In The Principles of Psychology (1890), he outlined the differences among “sensorial attention,” “intellectual attention,” “passive attention,” and the like, and noted the “gray chaotic indiscriminateness” of the minds of people who were incapable of paying attention. James compared our stream of thought to a river, and his observations presaged the cognitive “bottlenecks” described later by neurologists: “On the whole easy simple flowing predominates in it, the drift of things is with the pull of gravity, and effortless attention is the rule,” he wrote. “But at intervals an obstruction, a set-back, a log-jam occurs, stops the current, creates an eddy, and makes things temporarily move the other way.”
Interruptions at work can be maddening. Researchers at the University of California, Irvine, found after careful observation that the typical office worker is interrupted or switches tasks, on average, every three minutes and five seconds. And it can take 23 minutes and 15 seconds just to get back to where they left off. Jonathan Spira, author of “Overload! How Too Much Information Is Hazardous To Your Organization,” estimates that interruptions and information overload eat up 28 billion wasted hours a year, at a loss of almost $1 trillion to the U.S. economy.
Multitasking can take place when someone tries to perform two tasks simultaneously, switch . from one task to another, or perform two or more tasks in rapid succession. To determine the costs of this kind of mental “juggling,” psychologists conduct task-switching experiments. By comparing how long it takes for people to get everything done, the psychologists can measure the cost in time for switching tasks. They also assess how different aspects of the tasks, such as complexity or familiarity, affect any extra time cost of switching.
Meyer and his colleagues hope that understanding switching costs and the light they shed on “executive control” may help to improve the design and engineering of equipment and human-computer interfaces for vehicle and aircraft operation, air traffic control, and many other activities using sophisticated technologies. Insights into how the brain “multitasks” lend themselves to a range of settings from the clinic, helping to diagnose and help brain-injured patients, to the halls of Congress, informing government and industrial regulations and standards.