Christopher K Hsee and Adelle X. Yang, of the University of Chicago and Liangyan Wang, of Shanghai Jiaotong University conducted the study.
The obvious reasons are to make a living, earn money or even to help others.
"I think there's something deeper: We have excessive energy and we want to avoid idleness," said Hsee.
For the study, volunteers completed a survey, then had to wait 15 minutes before the next survey would be ready.
They could drop off the completed survey at a nearby location and wait out the remaining time or drop it off at a location farther away, where walking back and forth would keep them busy for the 15 minutes.
Either way, they would receive a candy when they handed in their survey.
Volunteers who chose to stay busy by going to the faraway location were found to be happier than those who chose to be idle.
And if the candies offered at the two locations were different, they were more likely to choose the far location-because they could make up a justification for the trip, Hsee and his colleagues said.
"If we can devise a mechanism for idle people to engage in activity that is at least not harmful, I think it is better than destructive busyness," Hsse said.
The research is published in Psychological Science.
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