Ever wonder why your resolve to hit the gym weakens after you’ve slogged through a soul-sapping day at work? It’s because willpower isn’t just some storybook concept; it’s a measurable form of mental energy that runs out as you use it, much like the gas in your car.
Roy Baumeister, a psychologist at Florida State University, calls this “ego depletion,” and he proved its existence by sitting students next to a plate of fresh-baked chocolate-chip cookies. Some were allowed to snack away, others ordered to abstain. Afterward, both groups were asked to complete difficult puzzles. The students who’d been forced to resist the cookies had so depleted their reserves of self-control that when faced with this new task, they quickly threw in the towel. The cookie eaters, on the other hand, had conserved their willpower and worked on the puzzles longer. Learn more here.