8/23/13 - you can't do two things at once

In today's selection -- you can't do two things that require concentration at once -- or at least you can't do them very well. And doing too much, even if not all at once, has a debilitating effect:

"The idea that conscious processes need to be done one at a time has been studied in hundreds of experiments since the 1980s. For example, the scientist Harold Pashler showed that when people do two cognitive tasks at once, their cognitive capacity can drop from that of a Harvard MBA to that of an eight-year-old. It's a phenomenon called dual-task interference. In one experiment, Pashler had volunteers press one of two keys on a pad in response to whether a light flashed on the left or right side of a window. One group only did this task over and over. Another group had to define the color of an object at the same time, choosing from among three colors. These are simple variables: left or right, and only three colors. Yet doing two tasks took twice as long, leading to no time saving. This finding held up whether the experiment involved sight or sound, and no matter how much participants practiced. If it didn't matter whether they got the answers right, they could go faster. The lesson is clear: if accuracy is important, don't divide your attention.

"Another experiment had volunteers rapidly pressing one of two foot pedals to represent when a high or low tone sounded. This exercise took a lot of attention. When researchers added one more physical task, such as putting a washer on a screw, people could still do it, sort of, with around a 20 percent decrease in performance. Yet when they added a simple mental task to the foot-pedal exercise, such as adding up just two single-digit numbers, (a simple 5 + 3 = ), performance fell 50 percent. This experiment revealed that the problem isn't doing two things at once so much as doing two conscious mental tasks at once, unless you are okay with a significant drop in performance. ...

"Despite thirty years of consistent findings about dual-task interference, many people still try to do several things at once. Workers of the world have been told to multitask for years. Linda Stone, a former VP at Microsoft, coined the term continuous partial attention in 1998. It's what happens when people's focus is split, continuously. The effect is constant and intense mental exhaustion. As Stone explains it, 'To pay continuous partial attention is to keep a top-level item in focus, and constantly scan the periphery in case something more important emerges.'

"A study done at the University of London found that constant emailing and text-messaging reduces mental capability by an average of ten points on an IQ test. It was five points for women, and fifteen points for men. This effect is similar to missing a night's sleep. For men, it's around three times more than the effect of smoking cannabis. While this fact might make an interesting dinner party topic, it's really not that amusing that one of the most common 'productivity tools' can make one as dumb as a stoner. (Apologies to technology manufacturers: there are good ways to use this technology, specifically being able to 'switch off' for hours at a time.) 'Always on' may not be the most productive way to work. One of the reasons for this will become clearer in the chapter on staying cool under pressure; however, in summary, the brain is being forced to be on 'alert' far too much. This increases what is known as your allostatic load, which is a reading of stress hormones and other factors relating to a sense of threat. The wear and tear from this has an impact. As Stone says, 'This always on, anywhere, anytime, anyplace era has created an artificial sense of constant crisis. What happens to mammals in a state of constant crisis is the adrenalized fight-or-flight mechanism kicks in. It's great when tigers are chasing us. How many of those five hundred emails a day is a tiger?' "


David Rock


Your Brain at Work


Harper Business


Copyright 2009 by David Rock


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