Why a Simple Promise Makes People More Honest
Can just saying “I promise to be honest” make people tell the truth? A large study in Norway and the U.S. shows that even simple, voluntary promises can significantly reduce lying—even when no one is watching.
Promises are often woven into our social fabric—spoken between friends, in business meetings, or before a courtroom oath. But how effective are they, really, in guiding moral behavior? A new international study conducted by researchers from Norway and the U.S. provides compelling evidence: making a promise—even one that’s unenforceable—can significantly reduce dishonesty.
The researchers ran three experiments involving 7,200 participants from the general population in Norway and the United States. Participants were invited to play a so-called “mind game” in which they could win $100 by claiming they had guessed the outcome of a dice roll. Since their original guess was never recorded, lying was impossible to detect—but tempting. About 28% of participants in the control group lied to claim the reward.
However, when participants were first asked to actively promise to report truthfully, dishonesty dropped by 25%, or 7 percentage points on average. Crucially, the promise had no consequences. It wasn’t enforceable and involved no penalty if broken. Still, people chose to lie less. The effect was equally strong in both countries and among all demographic groups.
Why does a simple promise work? The answer lies in the psychology of cognitive dissonance. When we actively commit to honesty, lying becomes psychologically uncomfortable—it clashes with our self-image as moral individuals. That inner conflict increases the moral cost of dishonesty, tipping the balance away from deceit.
Interestingly, the effect only held when the promise was made as an active choice. In versions of the experiment where “Yes” was pre-selected as the promise response, or where expressions of trust were added (“We trust you”), honesty did not improve. In other words, it’s not just about the words—it’s about the intentional act of promising.
These findings matter far beyond the lab. In an age of increasing misinformation, trust erosion, and institutional skepticism, the study offers a powerful insight: small, voluntary acts of moral commitment can have measurable effects. Promises might not change the world overnight, but they can nudge people toward better choices—especially when made freely and consciously.
The study is a reminder that honesty often begins not with rules, but with reflection—and a simple “Yes, I will.”