Your Brain Is Cheating on You, and You Don’t Even Know It

Sometimes, we cheat—not for money or prizes, but just to feel better about ourselves.

A new study reveals that people engage in “diagnostic self-deception,” tricking themselves into believing their success comes from ability rather than dishonesty. From underestimating calorie intake to inflating IQ scores, participants cheated even when there was no tangible reward, simply because it made them feel smarter or healthier. But when uncertainty about their abilities was introduced, cheating decreased. This raises an interesting question: how often do we lie to ourselves without even realizing it?

Fooling Ourselves to Feel Smarter

Fool me once, shame on you. Fool myself, and I might just believe I’m smarter.

A new study led by Sara Dommer, assistant professor of marketing at Penn State, explores why people cheat on tasks like crossword puzzles, Wordle, or calorie counting — despite having nothing tangible to gain. Her research suggests that when cheating helps boost self-image, people engage in diagnostic self-deception. In other words, they cheat but convince themselves their success is due to ability rather than dishonesty.

Dommer’s findings, published in the Journal of the Association for Consumer Research, reveal that people cheat even without external rewards like money or prizes — simply to feel smarter, healthier, or more accomplished. But for this self-deception to work, they must genuinely believe they aren’t cheating at all.

The Psychology of Self-Deception

“I found that people do cheat when there are no extrinsic incentives like money or prizes but intrinsic rewards, like feeling better about yourself,” Dommer said. “For this to work, it has to happen via diagnostic self-deception, meaning that I have to convince myself that I am actually not cheating. Doing so allows me to feel smarter, more accomplished, or healthier.”

Dommer conducted four studies to determine if people will cheat when rewards are solely intrinsic and what drives the feeling of accomplishment despite the cheating.

Calorie Counting: A Study in Self-Deception

In the first study, 288 undergraduate students received menu information about three days’ worth of meals — like three pancakes with butter — and were tasked with entering calorie information into a food-tracking app. The students were divided into two groups, with one group receiving additional calorie counts accompanying the meal descriptions.

The app listed five potential calorie options for each food entered. For example, the calorie counts for three pancakes with butter ranged from 300 to 560 calories. The group without specific calorie information could have averaged the five options to compensate for the missing information and get a better idea of the true caloric value of each meal, according to Dommer. Instead, participants in this group tended to enter fewer calories than the group that received specific calorie information, suggesting that people will cheat for intrinsic benefits, in this case feeling healthier.

Cheating on IQ Tests – And Believing It

The second study included 195 participants recruited on Amazon Mechanical Turk. These participants were divided into two groups — a control group and a cheat group — and asked to complete a 10-question, multiple choice IQ test. Those assigned to the cheat group were told that correct answers would be highlighted so they could keep track of their progress. After the exam, participants in the cheat group were asked to enter the number of questions they got correct, while the control group had to estimate their scores. Then the program graded both groups’ tests, and participants were asked to predict their score on an additional 10-question IQ test, this time one that did not allow for the possibility to cheat.

“I found that people do cheat when there are no extrinsic incentives like money or prizes but intrinsic rewards, like feeling better about yourself. For this to work. … I have to convince myself that I am actually not cheating.”

Sara Dommer, assistant professor of marketing

Self-Deception Strengthens False Beliefs

Dommer found that participants in the cheat group reported higher scores than those in the control group and, based on their self-reporting, overestimated their performance on the second IQ test. The results, she said, suggested that participants in the cheat group engaged in diagnostic self-deception, believing that their performance was due to their intelligence and not cheating, though their scores on the second test suggest otherwise.

Word Puzzles and Inflated Intelligence

The third study mirrored the second study, except this time 195 participants had to unscramble letters to find a word, like deciphering “utmost” from “motuts.” Individuals assigned to the control group had to enter their answers in an answer box, while those in the cheat group were shown the correct answer after 3 minutes and asked to self-report their scores. Then participants rated on a scale from one to seven, with one being “not at all” and seven being “very much so,” how much their intelligence and the task’s difficulty contributed to their performance. They used a similar scale to answer the question, “To what extent do you agree that unscrambling words is an accurate test of intelligence?”

Again, Dommer found that those in the cheat group reported successfully unscrambling more words than those in the control group. Compared to the control group, this group was more likely to attribute their performance to their intelligence and more likely to consider the task a legitimate test of intelligence.

“Participants in the cheat group engaged in diagnostic self-deception and attributed their performance to themselves,” Dommer said. “The thinking goes, ‘I’m performing well because I’m smart, not because the task allowed me to cheat.’”

The Role of Doubt in Reducing Cheating

The final study asked 231 participants to take a financial literacy test. Participants were divided into control and cheat groups, except this time the researcher had about half of each group read a statement about how most American adults cannot pass a basic financial literacy test. Dommer thought that introducing uncertainty about their own financial literacy may make individuals value accuracy over performance and reduce cheating. After taking the test, participants used a scale from one to seven to rate themselves on 15 traits related to financial literacy.

Dommer found that introducing the uncertainty statement decreased cheating as individuals sought more accurate measures of their financial literacy.

Can We Stop Self-Deception?

“How do we stop people from engaging in diagnostic self-deception and get a more accurate representation of who they are? One way is to draw their attention to uncertainty around the trait itself. This seems to mitigate the effect,” Dommer said.

The Hidden Risks of Believing Our Own Lies

Our society tends to think of “cheating” as a strategic, intentional act, Dommer said. This work, she explained, suggests that at times cheating happens beyond conscious awareness.

“I don’t think there’s a good cheating or a bad cheating,” she said. “I just think it’s interesting that not all cheating has to be conscious, explicit and intentional. That said, these illusory self-beliefs can still be harmful, especially when assessing your financial or physical health. When a person engages in diagnostic self-deception, they may underuse products and services designed to help them. This is why it’s important to be aware of illusory beliefs and strive to seek accurate self-assessments.”

Reference: “Acting Immorally to Self-Enhance: The Role of Diagnostic Self-Deception” by Sara Loughran Dommer, January 2025, Journal of the Association for Consumer Research.
DOI: 10.1086/732915

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