People cheat for money, prestige, or an edge over others. But a new study from Penn State suggests they also cheat for a different reason—to feel better about themselves. And surprisingly, they often manage to fool themselves into believing their success is real.

The study explores “diagnostic self-deception,” a process where people cheat yet convince themselves their performance reflects genuine ability. This allows them to feel smarter, healthier, or more capable, even when their success was, in part, a lie.

“I found that people will cheat even when there are no external rewards like money or prizes,” the researcher explains. “For this to work, they have to deceive themselves into believing they aren’t actually cheating.”

How the Study Tested Self-Deception

In four experiments, researchers examined whether people would cheat when the only reward was an inflated self-image.

• Counting Calories: In one study, 288 undergraduates entered meal data into a food-tracking app. One group received calorie counts, while the other had to estimate. Instead of averaging the given options for accuracy, those in the estimation group tended to report lower calorie values—making themselves feel healthier in the process.
• IQ Tests: In another study, 195 participants completed a multiple-choice IQ test. Some had correct answers highlighted (making cheating easy), while others did not. Afterward, those who had access to the answers overestimated both their scores and their intelligence, believing their success was due to ability rather than an unfair advantage.
• Word Scrambles: A similar pattern emerged in a word unscrambling task. Participants who saw the answers after three minutes still credited their intelligence for their performance. They were also more likely to believe the test was a valid measure of intelligence.
• Financial Literacy: In the final study, 231 participants took a financial literacy test. Some read a statement beforehand about how most Americans fail such tests. This introduced uncertainty about their own abilities, making them value accuracy over performance. As a result, they cheated less.

The Implications of Self-Deception

This study challenges the idea that cheating is always a deliberate act. Instead, people can cheat while genuinely believing they are playing fair.

“I don’t think cheating is necessarily good or bad,” the researcher says. “But illusory self-beliefs can be harmful, especially when assessing financial or physical health. When people deceive themselves, they may avoid tools or services that could actually help them.”

One way to counteract self-deception? Introducing doubt. When people were reminded of uncertainty, they cheated less, suggesting that a little skepticism—about oneself—can be a powerful tool for honesty.