That's the finding of new research published in the journal Psychological Science. Researchers from the University of Georgia recruited 51 students who performed two tasks to test self-control. The first task, which previous research has shown to deplete self-control, was tediously crossing out all the Es on a page from a statistics book.
Then, participants performed what is known as the Stroop task where they were asked to identify the color of various words flashed on a screen, which spell out the names of other colors. The Stroop task's goal is to turn off the student's tendency to read the words (which is easy to do) and instead see the colors (which is harder to do).
Half of the students rinsed their mouths with lemonade sweetened with sugar while performing the Stroop test, the other half with Splenda-sweetened lemonade. Students who rinsed with sugar, rather than artificial sweetener, were significantly faster at responding to the color rather than the word.
Why? It seems that the glucose in the lemonade triggers the brain's motivational centers simply by touching the tongue, giving the participants the extra push to complete the harder task.
"Researchers used to think you had to drink the glucose and get it into your body to give you the energy to (have) self control," said UGA psychology professor Leonard Martin, co-author of the study. "After this trial, it seems that glucose stimulates the simple carbohydrate sensors on the tongue. This, in turn, signals the motivational centers of the brain where our self-related goals are represented. These signals tell your body to pay attention."
Since glucose is the brain's primary energy source, it makes sense that a quick shot of sugar would crank up attention. But according to the researchers, this study suggests that the sugar is providing more than a simple energy boost.
"It doesn't just crank up your energy, but it cranks up your personal investment in what you are doing. Clicking into the things that are important to you makes those self-related goals salient," said Martin.
The theory behind Martin's statement is called "emotive enhancement," in which something (in this case sugar) leads a person to pay attention to their goals and not automatically act on an urge to stop investing self-control when they're feeling depleted. An example might be staying an extra half an hour at the gym when you're feeling like calling it quits.
"The glucose seems to be good at getting you to stop an automatic response such as reading the words in the Stroop task and to substitute the second harder one in its place such as saying the color the word is printed in," he said. "It can enhance emotive investment and self-relevant goals."
Not convinced? Well there's an easy way to test the findings and see if they hold up—just get a bottle of lemonade with real sugar and try gargling the next time you're ready to tap out. If you give it a try, please let us know how it turned out in the comments section.