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The Persistence of Deception and Self-Deception

Recent research shows that people become overconfident to persuade others.

By Joël van der Weele

The pop psychology shelf is full of books advocating self-confidence: If only you believe in yourself, success and social rewards will be yours. According to evolutionary biologist Robert Trivers, this may explain why most of us think we are better drivers, are kinder, and look better than others. Truly believing in your abilities and qualities facilitates persuasion by reducing giveaway tells and other obstacles to effective lying. After all, “It’s not a lie if you believe it."

The empirical evidence for these hypotheses is scant, however, because it is hard to know what people really believe. Self-help books mostly rely on anecdotal evidence and individual success stories. For instance, Donald Trump’s ascendancy to the presidency may plausibly stem from his weaponized sense of self-worth. But whether Trump really believes he is the best at everything is anybody’s guess. The same issue plagues academic studies showing that people who express higher confidence are perceived as more impressive.

To test whether true self-deception has social origins, my co-author Peter Schwardmann and I ran an experiment. We measured our subjects’ confidence about their intellectual ability by letting them bet on their own performance on an intelligence test, thereby putting money at stake for reporting accurate beliefs. Later in the experiment, subjects could earn additional money by convincing independent evaluators of their performance. To investigate self-deception, we compared the willingness to bet on their test performance between two groups of subjects: One group was told beforehand about the upcoming opportunity for persuasion, while another (control) group was not. This difference should not affect how people viewed their past performance, unless self-confidence is motivated by the wish to persuade others.

The evidence, just published in the journal Nature Human Behavior, confirms the strategic nature of confidence. Despite incentives to be as realistic as possible, subjects who knew about the future deception opportunity privately bet that they performed higher than did the control group. Thus, subjects persuade themselves before they persuade others. Furthermore, confidence about their performance causes subjects to be more convincing to their evaluators through both verbal and non-verbal channels, showing that (over)confidence pays in social interactions. Other recent papers and preprints have shown similar results.

These findings shine a new light on overconfidence, which has often been called a “bias” that is detrimental to decision-making. At the same time, Daniel Kahneman describes overconfidence as being “built so deeply into the structure of the mind that you couldn’t change it without changing many other things.” Our research suggests why: Truly held confidence comes with social gains, and our self-deception skills help us reap these gains.

This does not mean that we should be maximally overconfident. While some overconfidence may be good for you, too much may lead to big mistakes, (witness the billion-dollar losses by Trump the businessman) which may be exposed in the long run. Nevertheless, one would expect overconfidence to be most prominent in fields like politics and law, where persuasion is the core business, competition is high, and performance measures are noisy. Despite all its costs, overconfidence is truly part of the human condition.


Schwardmann, P., & van der Weele, J. (2019). Deception and self-deception. Nature Human Behaviour.

Solda, A., Ke, C., Page, L. & von Hippel, B., Strategically Delusional (2019). SSRN,

Smith, M. K., Trivers, R., & von Hippel, W. (2017). Self-deception facilitates interpersonal persuasion. Journal of Economic Psychology, 63, 93-101.