Inside the multitasking and marijuana study

A study came out in 2005 saying that multitasking lowers your IQ more than smoking marijuana does. David Freedman interviewed Dr. Glenn Wilson, author of the study. Wilson’s first response was “Oh, that damned thing.”

Someone from Hewlett-Packard contacted Glenn Wilson and asked him to conduct the multitasking study.

Encouraged by his sponsor at HP to keep the budget extremely low, and assured there was no pretense of trying to obtain scientifically valid, peer-reviewable, journal-publishable results, Wilson dragged eight students into a quiet room one at a time and gave them a standard IQ test, and then gave each of them another one — except that the second time, he left either a phone ringing continuously in the room or a flashing notification of incoming e-mail on a computer monitor in front of them.

Wilson said “It didn’t prove much of anything, of course.” But the study made a huge splash.

I don’t imagine anyone would be surprised that a constantly ringing telephone would reduce your ability to concentrate on an IQ test.  And comparing the result to marijuana use is pure sensationalism. While hearing a phone ring and smoking marijuana both impair concentration, they’re obviously not comparable.

Artificial studies like this one fail to answer the more important question of what effect  voluntary multitasking has on creativity and productivity. As Tyler Cowen says

To sound intentionally petulant, the only multitasking that works for me is mine, mine, mine!  Until I see a study showing that self-chosen multitasking programs lower performance, I don’t see that the needle has budged.

Paul Graham made a similar observation.

The danger of a distraction depends not on how long it is, but on how much it scrambles your brain. A programmer can leave the office and go and get a sandwich without losing the code in his head. But the wrong kind of interruption can wipe your brain in 30 seconds.

I’m convinced that multitasking, even voluntary multitasking, does decrease creativity and productivity. But I reached that opinion from personal experience, not based on any study of people taking IQ tests while listening to a phone ring. And of course some activities pair more effectively than others. Sweeping floors while listening to an iPod works better than checking email while taking an IQ test.

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6 thoughts on “Inside the multitasking and marijuana study

  1. Excellent post.

    I find that when I am working on hard problems (hard mathematical problems), I tend to voluntarily multitask. However, when I revise a manuscript, or write anything relatively easy (code or English), I avoid multitasking.

  2. I find as I get older that ordinary events can wipe my thought processes clean in milliseconds. When I am working on a difficult and thought provoking problem, I try to avoid interruption and “soldier on” to complete the task “come hell or high water”.

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