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Willpower is in your mind, not in a sugar cube, say Stanford scholars

The research challenges the popular view that willpower is a limited resource that depends on a consistent supply of glucose.

Sergey Nepsha / iStock piece of cake

It's not an extra dose of sugar that boosts willpower, researchers say. The proper mindset does the trick.

That afternoon candy bar may not be the best way to power through the rest of the day's tasks.

A new study by Stanford psychologists argues that you don't need sugar for a performance boost. A change in mindset will do.

Through a series of experiments, the Stanford team examined participants' beliefs about willpower – defined as the ability to resist temptation and stay focused on a demanding task ­– and tested whether, and when, they experienced a lull in it.

"The dominant theory about willpower is that it's easily depleted and depends on a consistent supply of glucose from the outside," said Carol Dweck, professor of psychology and one of the study's authors.

But researchers found that people who believed willpower was abundant didn't need sugar to persevere through two difficult tasks.

"When you have a limited theory of willpower, you're constantly on alert, constantly monitoring yourself. 'Am I tired? Am I hungry? Do I need a break? How am I feeling?' " Dweck said. "And at the first sign that something is flagging, you think, I need a rest or a boost."

She said people who have the more-abundant theory aren't looking for those cues all of the time.

"We're not saying people don't need fuel for strenuous work, they just don't need it constantly," Dweck said. "People have many more resources at hand than they might think."

The findings were published last week in the journal Proceedings of the National Academy of Sciences. The research team included Greg Walton, an assistant professor of psychology at Stanford, and Veronika Job and Katharina Bernecker of the University of Zurich.

The team believes there are important implications in society, where people struggle with diabetes and obesity, if people overuse sugar to tap into their willpower.

"It's really important for them to know that in order to keep on working on a task ­– be it a diet or job assignment or school work – they don't have to ply themselves with sugar as some earlier studies have suggested," Dweck said.

The researchers found that people could be taught to think differently about willpower and that affected whether sugar helped their performance.

"We put them in different mindsets, either believing willpower is limited or believing it's more self-generating," Dweck said.

The result, again, was that people who were led to believe willpower was abundant did not show depletion and the sugar didn't help them. However, the people who believed willpower was limited did do better on a difficult task after a sugary drink.

Dweck said they don't yet know why certain people believe one theory over the other.

"We want to design interventions to teach people how to harness their considerable willpower," she said.

Media Contact

Carol Dweck, Psychology: dweck@stanford.edu

Brooke Donald, Stanford News Service: (650) 725-0224, brooke.donald@stanford.edu