Overload

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.

Wray Herbert writes the "We're Only Human . . ." blog at www.psychologicalscience.org/onlyhuman .

© 2008