Don’t Bother Doing More Than You Promised

Breaking a promise is costly, but exceeding it might not be worth the effort. That’s the main finding in work by Chicago Booth’s Nicholas Epley and University of California, San Diego’s Ayelet Gneezy.

In a series of experiments, the researchers asked participants to rate how they felt after experiencing promises that had been broken, kept, or exceeded.

In one experiment, researchers told 60 undergraduate students that they could solve up to 40 puzzles and would receive compensation per puzzle solved. But since they wouldn’t have enough time to solve all 40 puzzles alone, each study participant was paired with a volunteer who promised to solve 10 of the puzzles. The students did not know that Epley and Gneezy had instructed some volunteers to solve 10 puzzles, and others to solve five or 15 puzzles instead.

Before and after the experiment, the researchers had study participants fill out several surveys. One indicated how much effort they thought their volunteer-partners had invested in keeping their promise, rating the level of effort on a scale of 1 to 11, with 1 representing “very little effort,” and 11 “extreme effort.” Another weighed how happy they were, on a scale of −5 to 5. As expected, participants valued keeping a promise more highly than breaking one. However, students said exceeded promises made them no happier.

Epley and Gneezy also found that the surveyed students felt the participant-volunteers who broke promises had expended less effort than those who’d kept them. But when asked about people who did more than asked of them, participants didn’t notice the extra effort—in their view, people who exceeded their promises worked no harder than people who simply kept promises.

Epley and Gneezy postulate this same behavior extends to more abstract relationships, including social-contract norms in business settings. Companies laboring to exceed promises made to customers or employees “may not produce the desired consequence beyond those obtained by simply keeping promises,” the researchers write.

So if you promise your boss you’ll stay late to finish a project on time, don’t try to impress her by working through the weekend to finish it ahead of schedule. The research suggests that your boss will be just as happy if you simply fulfill your promise, and you can spend the extra time doing things you enjoy.