Into the Mind and Heart of the Liar

People who constantly tell lies seem to have everything figured out when it comes to deceiving others. The smooth talker seemingly can get away with almost anything. On the other side of this are those who are lied to. Most people are willing to trust others without trying to peer too deeply into their motives. But there are times when even the most trusting person can tell if something seems “off.”

A Four-Pronged Approach to Lying

As noted by Marburg University’s Tabea Wächtershäuser and Kristina Suchotzki (2026), “lying is more cognitively demanding than telling the truth.” You really have to make sure that you cover all your bases when you lie to avoid any inconsistencies. The truth can be inconsistent too, but the process of summarizing actual reality doesn’t require that you fact-check everything you say. That constant monitoring of your verbal output means that your brain is on overtime, invoking what is called “response inhibition.”

The emotional aspects of lying aren’t as clear. The liar may experience guilt, glee, or anxiety. Lying about one’s own past, though, is more likely to lead to more nervousness and tension. However, it is possible that good liars can muster their emotional intelligence to manage their arousal.

These issues are partially resolved, believe the authors, in what’s called the “Activation-Decision-Construction-Action” theory. As the name implies, liars go through a four-stage process of activating the truth, deciding whether to tell it or not, constructing the lie, and then telling it. Emotions make all of this harder, but again, it’s not clear which emotions get in the way of the liar’s ability to think.

Putting Liars to the Test

Using an experimental manipulation in two separate studies, the Marburg U. researchers compared the cognitive load and emotional responses of participants instructed to lie vs. tell the truth. Participants (average ages 22 and 26) were first told to perform a mock crime involving a minor theft (USB stick in one experiment, 1,000 Euros in the second). Then they responded to questions designed to compare their response times and emotional ratings regarding whether they committed the crime. In the lying condition, they were told not to tell the truth, and in the deceptive condition, they were told to lie. Their cognitive and emotional reactions were then tracked across the two conditions.

To give you a sense of what kinds of questions the researchers used, these are sample items:

Cognitive processes:

How cognitively demanding did you find this task?

Did you cognitively focus on switching between lying and telling the truth while responding?

Did you follow a strategy while responding?

Emotional responses:

Did you feel proud while responding?

Did you feel afraid while responding?

Did you feel nervous while responding?

Did you feel guilty while responding?

Think about how you might have responded if you’d been in the mock crime-deception condition. As you can see from these sample items, the cognitive questions assessed the amount of effort and control required to lie, and the emotional questions tapped a range of positive and negative feelings.

As the authors predicted, it took longer for participants to lie than to tell the truth. Supporting the Activation-Decision-Construction-Action theory, participants rated all of the components this theory proposes as more cognitively demanding. They also reported higher levels of fear, nervousness, and distress. These findings support the idea, in the words of the authors, that “emotional processes contribute to the prolongation of response times.”

What to Do When Confronted With a Liar

The experimental method used in the Marburg U. study comes close to real-life situations when an individual is trying to deny the truth of their actions. One major difference is that the participants knew that their crime would be easily detected because, much like the child with a hand in the cookie jar, the researchers were in charge of the entire situation and knew about the crime. In real life, the liar proceeds from the assumption that the lie will go undetected barring some type of giveaway.

The question then becomes whether you, if faced with a lie, will know what to look for in the liar’s behavior. It’s a well-known fact that liars can cover up the clues to their lying through manipulation of verbal and non-verbal (eye gaze, body language) channels. Using the cognitive and emotional cues could very well provide you with a more reliable method of getting to the truth.

That reaction time clue would be your first hint. You’re pretty sure that a friend of yours is offering a fake excuse for failing to follow up on a promise. As you hear the retelling of what went wrong, use any stumbling around or hesitation as a possible sign. Getting next to the emotional component of lying, see if you sense the edges of negative emotions such as fear or guilt.

The cognitive and emotional clues should work better for someone you know than they would for a stranger because you have a baseline of how your friend ordinarily behaves. With a stranger, you might have to conduct your own mini-experiment to see whether you’re being handed a falsehood or not. A seasoned liar may be able to pull it off, but knowing that it is more cognitively taxing to deceive you can help you interpret small nuances of hesitation or emotional stress.

To sum up, the chronic liar may have a pretty good set of cognitive and emotional tools to cover up the truth. Knowing that these tools can break down can help you get to the answers you need.

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