It could happen to students cramming for exams, people working long hours or just about anyone burning the candle at both ends: Something tells you to take a break. Watch some TV. Have a candy bar. Goof off, tune out for a bit and come back to the task at hand when you're feeling better. After all, you're physically exhausted.
But a new study from Stanford psychologists suggests the urge to refresh (or just procrastinate) is well all in your head.
In a paper published this week in Psychological Science, the researchers challenge a long-held theory that willpower defined as the ability to resist temptation and stay focused on a demanding task is a limited resource. Scientists have argued that when willpower is drained, the only way to restore it is by recharging our bodies with rest, food or some other physical distraction that takes you away from whatever is burning you out.
Not so, says the Stanford team. Instead, they've found that a person's mindset and personal beliefs about willpower determine how long and how well they'll be able to work on a tough mental exercise.
"If you think of willpower as something that's biologically limited, you're more likely to be tired when you perform a difficult task," said Veronika Job, the paper's lead author. "But if you think of willpower as something that is not easily depleted, you can go on and on."
Job, who conducted her research at Stanford and is now a postdoctoral scholar at the University of Zurich, co-authored the paper with Stanford psychology Professor Carol Dweck and Assistant Professor Greg Walton.
The researchers designed a series of four experiments to test and manipulate Stanford students' beliefs about willpower. After a tiring task, those who believed or were led to believe that willpower is a limited resource performed worse on standard concentration tests than those who thought of willpower as something they had more control over.
They also found that leading up to final exam week, students who bought into the limited resource theory ate junk food 24 percent more often than those who believed they had more control in resisting temptation. The limited resource believers also procrastinated 35 percent more than the other group.
"The theory that willpower is a limited resource is interesting, but it has had unintended consequences," Dweck said. "Students who may already have trouble studying are being told that their powers of concentration are limited and they need to take frequent breaks. But a belief in willpower as a non-limited resource makes people stronger in their ability to work through challenges."
The Stanford researchers say their findings could help people who are battling distraction or temptation: diabetics following strict diets, people trying to overcome addictions, employees facing a tight deadline.
"This is an example of a context where people's theories are driving outcomes," Walton said. "Willpower isn't driven by a biologically based process as much as we used to think. The belief in it is what influences your behavior."
Explore further: Don't throw the candy out: Temptation leads to moderation