Mind: Why Multitaskers Fail

You've just moved to town and need a place to live. You've narrowed your choices to three apartments that seem suitable. The first is spacious, 800 square feet, but it's a good 15 miles from your new job. That's a long daily commute. The second is much closer, only about seven miles away, but at 450 square feet the space is a bit cramped. The third is 350 square feet and 10 miles from work. You're running out of time and need to get yourself settled. Which do you choose?

Well, if you're like most people, you will choose the second apartment. That may be a perfectly fine choice, and chances are you'll be happy there. But it's not a rational choice, and here's why: Eliminating the third apartment is a no-brainer; it's both smaller and more remote than the second apartment. So that should leave you with a tossup between two decent places, and you should be just as likely to choose one as the other. But you're not. Instead you are irrationally swayed by the similarity between the second and the third apartments. You pick the second not because it is better than the spacious apartment, No. 1, but because you're still comparing it to the loser apartment, even though you ruled that one out.

Cognitive psychologists call that third apartment a mental "decoy." It is so clearly inferior to the other two, neither spacious nor well-located, it really shouldn't even be in the mix, but dinging it does not make it go away entirely. It lingers in your mind, tugging you toward apartment No. 2.

This is not a good thing. We make choices like this every day. We decide where to go to college, what to eat for dinner, who to date. And a lot of our choices are irrational, influenced by irrelevant information. We are of course capable of making deliberate, logical choices as well; recent science suggests that the brain is like a hybrid engine, constantly switching back and forth between reasoned calculation and rapid intuition. But what determines how we will handle a particular problem in life? How do we know what part of our cognitive repertoire will be in play today?

A couple of Florida State University psychologists may have part of the answer to that. If the brain truly is like a hybrid engine, E. J. Masicampo and Roy Baumeister reasoned, then why not look at the fuel system? All of that cognitive crunching doesn't come cheap, and effortful deliberation is especially greedy for energy. This is not just a metaphor: they wanted to see if the brain's supply of fuel--blood glucose--might determine whether we make logical choices or irrational ones. They decided to explore this in the laboratory.

The experiment was fairly simple. They started by having all the subjects do an exercise meant to deplete their power--both their willpower and the glucose that fuels self-control and decision making. Specifically, they had them watch a silent video of a woman talking. A series of words also flashed on the screen, but they told the subjects to ignore the words; if they did find themselves distracted by the words, they were to refocus their attention on the woman. This is actually very hard to do; it requires a lot of mental effort to not read the words right in front of you.

The purpose here was to mentally "exhaust" the subjects, much like doing wind sprints would deplete their muscles and lungs. Once they had all of them in this depleted condition, they re-energized only some of them with sugar. They actually had all of the subjects drink some lemonade, but only some were getting real sugar; the others were drinking lemonade artificially sweetened with Splenda. The idea was that the Splenda drinkers would remain cognitively drained while the sugar drinkers would be restored to normal intellectual functioning.
Finally, the psychologists confronted the subjects with the apartment dilemma described before. In theory, the depleted subjects should at this point have been mentally "weaker" and therefore less capable of making effortful, deliberate decisions. And that is precisely what they found. As reported in the March issue of the journal Psychological Science, the subjects who were running on empty were much more likely to be swayed by the decoy apartment--and thus to make a poor judgment. Those who had recently been re-energized didn't waste any time or energy on the inferior decoy, and didn't allow it to sway them in their real choice: they chose the spacious apartment and the better-located apartment about equally.

This is obviously not about lemonade and apartment hunting. But it is about the intricate interplay of mind and body in so many of life's dilemmas. Imagine that you are trying to simultaneously quit smoking, hold your temper with your foolish boss, plan a wedding and finish a complex deadline project while helping your kid with his algebra. Many of us pride ourselves on our ability to multitask. But if willpower and mentally strenuous work both require the same fuel, and that fuel comes in limited supply, something along the way probably has to give. It's just a matter of what.