When to believe lies

Why truth is our default

Exploring how our natural inclination to believe in the honesty of others shapes our communication and social interactions. Tim Levine uncovers the reasons behind our vulnerability to deception and highlights the benefits of defaulting to truth and its role in the development of human civilization, culture, and relationships.


Communication is an essential part of being human. Communication allows up to us learn from others and to pass along things we have learned to others. With communication, we can cooperate with other people and coordinate our activities to accomplish tasks and goals that are not individually possible. Forming meaningful and lasting relationships with other humans requires communication. Effective and efficient communication enables human civilization, scientific and technological progress, and the creation and transition of human cultures.

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Join me for a moment in a thought experiment. Imagine a communication ecology where truth and honesty were not the default. Communication could not and should not be trusted in such a dystopian world. We would all bog down in uncertainty. Assessing the veracity of every incoming bit of information is an unthinkable burden. Communicative solipsism would be deeply dysfunctional.

I am the author of truth-default theory and the book Duped: Truth-default Theory and the Social Science of Lying and Deception [1]. Truth-default theory is a social scientific theory that seeks to makes sense out of some puzzling findings from research on human-to-human deception and deception detection. The central most idea is that truth and honesty are the default modes of communication. People are typically honest unless they have a specific reason to communicate deceptively, and people tend to believe others unless suspicion, skepticism, or doubt is actively triggered. Conscious thoughts of honesty or dishonesty do not come to mind unless there is a motive or trigger. For example, until reading this sentence, most readers will not have wondered if I really wrote Duped, or if truth-default theory is really a thing. After reading this, consideration of veracity is brought to mind (i.e., “triggered”), but most readers still will not seriously entertain that this article might be fiction. Fortunately, I lack a reason to misrepresent my ideas. My interests are served well by being honest. This is the case here, and it is the case in most but certainly not all communication situations.

Before there was a truth-default default theory, there were experiments giving people lie detection tasks of various sorts. People were shown some number of communications, and asked to sort the truths from the falsehoods. Across hundreds of studies with many variations, a robust and coherent collection of findings emerged [2]. First off, in real-time assessments, people invariably performed poorly. The average was 54% correct, where chance was fifty-fifty. Second, people believed more often than they doubted. That is, even when explicitly prompted to assess veracity with forewarning of the possibility of deceit, people were still truth-biased. Consequently, participants in lie detection tasks got honest messages right more often than they correctly identify falsehoods as false.


In most communication, the possibility of deception does not even come to mind


Something very different, however, happens in social science experiments involving deception but that are not about deception. Perhaps the most famous (or infamous) example is Milgram’s obedience experiments in which research participants are instructed to electrocute a person who they think is another participant [3]. A disturbing number of people just followed orders believing that they were inflicting great pain or worse. Apparently, none of them the detected the experimental deceptions. The victim was an actor and the shocks were faked. The extent of obedience varied in Milgram’s experiments, but all the subjects were duped by the experimental set-up.

One big difference between deception detection experiments and experiments like Milgram is that the people in deception detection experiments know that they need to be on guard for deception and they are required, as part of the research, to assess veracity. In truth-default theory language, the triggering is impossible to miss. This, however, is not the case with most communication. In most communication, the possibility of deception does not even come to mind. This, I argue, is a very good thing.

One implication of defaulting to the truth is that on the reception side of communication, we are all very vulnerable to being duped. We humans do not seem to like thinking that we have this vulnerability. Who wants the self-knowledge that they are easily duped? I have heard the argument that because humans evolved the ability to deceive others, we therefore must have evolved the ability to detect deception. I make a very different argument.

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First, I believe that the truth-default offers a huge survival advantage. The benefits we get from efficient and effective communication out weight the costs of being duped once in a while. I started this essay off by listing some of the most advantageous payoffs from efficient and effective communication, and the alternative is not very plausible.

Second, most communication is honest. We also default to the truth on the production side of communication. People are honest unless they have a motive for deception. Truth-default theory holds that people are probably a lot more honest than you think.

To test this out, my colleagues and I have been conducting surveys and experiments asking people about how often they lie or observing responses in different situations where there is or is not a reason to lie. What we find is that when the truth works just fine for our communication goals, people are invariably honesty. When there is a clear motive to lie such as for politeness, to make a desirable impression, to hide a punishable transgression, some people are dishonest while others are honest even though they have an incentive not to be. Regarding how often people, most people tell few lies on any given day, and most lies are told by a few prolific liars. Of the lies that are told, the vast majority are minor and inconsequential. Lying is rare relative to honesty, and lies of consequence are even less common.


Truth-default offers a huge survival advantage. The benefits we get from efficient and effective communication out weight the costs of being duped once in a while


Because honesty is so much more prevalent than deception, we only need to be on guard for deception with some people in some situations. Constant vigilance for deception counterproductive.  

Third, evolving real time deception detection ability is not the only solution to the problem of deception. Humans, I argue, rely on culture and socialization. Parents everywhere teach their children not to lie. Every major world religion prohibits deception. Prevention, I argue, is much more efficient than constant surveillance.

Finally, when lies are about important things, the truth tends to come out. My colleagues and I have found is that most lies are detected after the fact. When we detect an important lie, we can tell others that the liar should not be trusted, and they can be ostracized or shamed.

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Of course, people do seek to deceive others and people can be skeptical. But this is not communication business as usual, and this is a good thing. This is why the truth is our default.

Overall, the truth-default plays a significant role in our daily communication and social interactions. While it has its drawbacks, the benefits of efficient communication and trust-building outweigh the risks of occasional deception.


  1. Levine, T. R. (2020). Duped: Truth-Default Theory and the Social Science of Lying and Deception. University of Alabama Press.
  2. Bond, C. F., Jr., & DePaulo, B. M. (2006). Accuracy of deception judgments. Personality and Social Psychology Review, 10, 214-234. doi.org/10.1207/s15327957pspr1003_2
  3. Milgram, S. (1969). Obedience to Authority. Harper.
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