From NHH to a prestigious postdoc in economics
PhD candidate Paula Navarro Sarmiento has secured a postdoctoral position at CEMFI in Madrid, one of Europe’s top research institutes in economics.
Imagine you could lie for $100 — and no one would ever know
Would you do it? A new study reveals how a single promise can tilt the scales toward honesty.
In courtrooms, classrooms, boardrooms — and even when signing tax forms — we are often asked to promise to tell the truth.
But do promises really change our behavior?
A new study published in Journal of Economic Behavior & Organization (see facts) suggests they do — and surprisingly well.
`Even a simple, non-binding promise can reduce dishonesty by 25 percent. And it works not because people are afraid of getting caught — but because we want to live up to our own moral standards´ says Bjorvatn.
Personal promise
The researchers at NHH and University of Mexico conducted three large-scale experiments with more than 7,000 participants in Norway and the United States. In the experiments, participants were asked to think of a number from 1 to 6, then roll a die. If the number they had "guessed" came up, they would win $100 (or NOK 1 000).
Making a promise
Making a promise increases the moral cost of lying: Evidence from Norway and the United States in Journal of Economic Behavior Organization. Mathias Ekström, Kjetil Bjorvatn, Pablo Soto Mota, Hallgeir Sjåstad. The study is based on three large-scale experiments with over 7,000 participants from Norway and the United States.
But here ‘the twist.: No one could verify their guess. The only person who knew the truth was the participant.
Without any honesty prompt, about one in four chose to lie for the money. But when participants were first asked to make a personal promise to tell the truth, dishonesty dropped by 25 percent.
`This is a striking result, especially given that the promise carried no legal or social consequences´, says Ekstöm.
It’s a very simple intervention, according to the researchers:
`Just a short sentence asking people to promise to report truthfully — and yet it consistently reduced dishonesty across different countries, age groups, and political orientations´, says Ekström.
Promises, not pressure
The study also found that simply telling participants they were “trusted” had no effect on their behavior. It wasn’t about how others viewed them — it was about how they saw themselves.
In other words, the promise only worked when participants made an active choice. Those who simply received a default message (“we assume you promise”) behaved no differently than those who made no promise at all.
`What matters is not the formality or enforcement of the promise, but the act of personally committing to it, ´explains Bjorvatn.
Moral costs — not just legal ones
The study builds on theories of cognitive dissonance and moral psychology, suggesting that when people actively promise to be honest, it creates internal tension — making lies feel worse, even in private.
In a time when ethical behavior is under pressure in politics, business and AI, the findings suggest that simple social norms — like making a promise — still hold real psychological power.
`Our findings may have implications for policy and practice in areas where self-reported honesty is important, such as taxation, insurance, or academic honesty. We believe that creating situations in which people commit to honesty may increase truthful reporting, even when enforcement is minimal, ´says Ekström.
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