Why do people lie?

by Valerie Starratt, PhD

5 minutes

What do a dog, chimp, gorilla, and cuttlefish all have in common with people?

We all lie. And all for the same reason.

Let’s go ahead and get the bottom-line answer out of the way right up front.

People lie because lying helps them get something they want or avoid something they don’t want. 

It might seem like an obvious and simplistic answer, but that’s only because it is. It’s also correct.

The behavior of lying is often explained with discussions about ethics and morality, and maybe religion. People differentiate between white lies and malicious lies. They add in the roles of Theory of Mind and Executive Functioning. Those things are all fine to include in the larger conversation, but at the end of the day they’re not strictly necessary for understanding why people lie.

Here’s what I mean. To lie is to engage in the behavior of deception. It is the attempt to communicate a piece of information that is in some way inconsistent with reality or perceived reality. People lie every day, but so do many other animals.

One of my favorite examples of non-human deception is the male cuttlefish, which we sometimes call sneaky fu… uh, that is… sneaky fornicators. This is because some smaller, less physically impressive males employ a mating strategy that involves changing their shape and color to look like females in order to sneak past the more impressive males and gain access to the ‘other’ females. Of course, to those females, they present themselves as perfectly typical males. Sometimes, individual male cuttlefish present two displays at once: male to the front facing the female potential mate and female to the back facing the rival male. Clearly, this is deception.

If you have spent much time around dogs, you’ve likely seen them engage in deception. Dogs are well known to steal a treat or a toy and hide it somewhere until whomever they stole it from is unlikely to catch them eating or playing with it. My own dog will routinely bark her something-is-terribly-wrong bark so I get up to investigate only for her to immediately hop up and comfortably settle into the space I just left free on the couch or bed.

Chimpanzee deceptions are also quite well studied. One chimpanzee will lead another toward a comparatively low-value stash of food only to go back later alone for the higher-value stash they kept hidden. The first chimpanzee will even avoid looking in the direction of the higher-value hidden stash when in the presence of another chimp so as to not give away the secret. 

A fantastic specific example of non-human animal deception is Koko the gorilla. Koko had been taught sign language and was able to communicate incredibly well with the researchers who worked with her. Koko also happened to love cats, and herself had adopted a kitten. Anyway, one day Koko was apparently having a bit of a bad day and threw a tantrum during which she ripped the sink out of the wall in her habitat. When her humans discovered this and asked her what happened, Koko signed “cat did it” and pointed to her kitten. What is there not to love about a gorilla blaming a kitten for property destruction?

But here’s the thing. If you read any of the literature on these kinds of non-human animal behaviors, it likely includes words like ‘deception’ or ‘tactical deception’. What is tactical deception, you ask? It is the act of engaging in a behavior to mislead another individual in a way that benefits the deceiver. 

How is this different from lying?

It’s not. 

If you talk about humans lying, people will try to bring in arguments about intentionality, philosophical and cultural influences, and a thousand other things. If you talk about animals engaging in deception, people readily accept the simple and direct argument that deception is a strategy for pursuing a beneficial outcome. 

But the thing is, humans ARE animals and people DO lie in order to benefit themselves.

If we can all agree to the established fact that cuttlefish and dogs and gorillas engage in deception because it benefits them, why do we need to come up with a different and far more complicated explanation for why humans engage in the same behavior?

This isn’t to suggest that humans or any other animal will always lie whenever there is a benefit to be had from lying. They obviously don’t. They do, however, lie when there is a net benefit to engaging in deceptive behavior. That is, when the benefits outweigh the costs. It’s a simple cost-to-benefit ratio.

Why does any of this matter?

For the same reason understanding any behavior matters. If we understand a behavior we can predict and (attempt to) modify it.

Let’s take a benign example.

As a professor, I genuinely wanted my students to understand the material I was trying to teach them and to let me know if there was anything they didn’t understand. I was constantly asking “does that make sense?” and “is any of what we just discussed unclear?”. More often than not, I was met with answers that indicated they understood the material even though I 100% knew they didn’t.

They were attempting to deceive me about their level of understanding. Why? The benefits outweighed the costs for them. What were those benefits and costs? Well, the benefit was that they avoided negative attention (looking stupid, etc.). The cost? Minimal. What does it really matter if a student doesn’t understand something they probably never cared about or wanted to learn about in the first place? [Full disclosure: I often taught statistics to undergraduate students at 8am. I assure you very few undergraduate students inherently care about understanding statistics at 8am.]

Regardless of how they felt about the material, as their professor I wanted them to understand it. And so I needed them to admit to me what they didn’t understand so I could try a different strategy. All I had to do was change the cost-to-benefit ratio of their deception.

This is the tricky part, and often the part that people get wrong. Chastising them for not being honest would only increase their likelihood of doubling down on their deception. Because what does chastising do? It increases the benefit of lying. If they lie, they’ll avoid being the target of negative attention and all I’m offering is negative attention. 

Instead, I took the approach of offering effusive praise to any student who gave even the slightest indication that they had questions and assured them that their question or misunderstanding was a very common one. If they don’t have to worry about looking or feeling stupid, that reduces the benefit of deception.

Simultaneously, I could increase the cost of deception. An easy way to do that in this instance was to remind the students that the material would be on the exam. In doing that, the cost increased from virtually nothing–not understanding something they didn’t care about anyway–to having a negative impact on their exam grade. For some students, this was a snowballing cost, with a bad exam score leading to a bad course grade leading to threats to their scholarship or position as a varsity athlete.

By increasing the cost and reducing the benefit, I could decrease the likelihood of the deception.

It’s not always that simple. Sometimes the benefits of a lie can be life changing, and there’s no cost too great to overcome it. Often the costs of a lie are dependent on getting caught, and so whether the costs outweigh the benefits are dependent on the level of risk a person is willing to accept. And for the record, the guilt and shame that many people experience when they lie or consider lying is absolutely a cost, one that may all but prohibit lying. But not everyone experiences guilt or shame when they lie. On the contrary, some people get a release of dopamine, one of the brain’s feel-good chemicals, when they lie. 

All this means is that there are substantial individual differences in what counts as a cost and what counts as a benefit for people when it comes to lying. But at the end of the day, the logic is the same. 

People lie because it benefits them.