How to Catch a Liar: The 3 Things You Can Do to See if Someone is Lying

How do you catch a liar? It’s not so easy. Liars usually suppress the trust inwardly and may also outwardly monitor their movements in order to appear honest. For example, they’d try to maintain eye contact and avoid other traditional giveaways.

Because of this, liars tend to utilise more cognitive resources than truth tellers in order to maintain their story, so they increase their vulnerability of being exposed. If cognitive demand is raised, liars may be unable to effectively cope with additional requests  and inadvertently reveal their deception.

To detect deception, you should manipulate this process by placing extra cognitive demand. This increases the likelihood of the liar slipping up and revealing some cues of deception that you can pick up.

If you’re an interviewer, or someone just looking to detect deception, below are some common cognitive stress / overload techniques you can use:

1. Ask Them to Describe Things in Reverse Order

Try reciting the alphabet backwards.

What, you can’t? It’s too mentally taxing? Now imagine trying to maintain a consistent lie while describing it in reverse order. That’s not going to be easy.

Asking someone to describe an event backwards provides more opportunity for mistakes in the story’s timeline. Describing an event in reverse increases cognitive load because:

(a) it runs counter to the natural forward-order coding of sequentially occurring events

(b) it disrupts reconstructing events from a schema.

In a psychology deception study, for example, college student participants were interviewed by a police officer about a staged theft.

The video-taped interviews, in which the reverse order strategy was utilized, were later played for police officers. The officers were able to detect lying 60% of the time compared to 42% of the time in the control condition (chronological order), consistent with the greater verbal and nonverbal cues determined to be present in the first group.

2. Ask Unexpected Questions

Another method of increasing cognitive overload is by asking irrelevant questions.

A liar is less likely than a truth teller to answer irrelevant questions accurately and with ease because maintaining the fictional story causes other cognitive processes (e.g. the ability to quickly process and respond to unexpected questions) to become more difficult.

Relevant to revealing a person’s true motivation, the devil’s advocate approach was developed to detect deception in expressing opinions. An interviewer (after listening to the subject’s opinion) might unexpectedly ask the person to argue against his stated personal view. “Playing devil’s advocate,” the interviewer might ask, “is there anything you can say against…?”

An example of this in practice would be an interviewer first asking a question that forces the interviewee to argue for his personal view – “What are your reasons for supporting the Americans in the war in Afghanistan?” The interviewer then asks the interviewee to argue against his personal view – “Playing devil’s advocate, is there anything you can say against the involvement of the Americans in Afghanistan?”

Generally, people will have given more thought to and will find it easier to generate reasons supporting their underlying beliefs rather than reasons opposing them.

3. Look for the Details 

Truth tellers are usually able to relate events in much greater detail and with greater plausibility than liars.

Therefore, an interviewer may increase the observable differences between truth tellers and liars by establishing an expectation that the interviewee will offer a high level of detail. In this case, interview style plays an important role in encouraging interviewees to talk.

Research found that among police officers interviewing suspects, an accusatory interview style contained the fewest verbal cues to deceit, partly because it led suspects to make short denials. Information-gathering interviews and behavior analysis interviews led to better results in lie detection.

In other words, a cooperative, truthful witness is more likely to give greater detail when speaking with an encouraging interviewer rather than one who appears neutral or suspicious. Ostensibly, this expectation of detail will increase cognitive demand on liars trying to reach and maintain the higher standard.

See also: How to Tell if Someone is Lying: The 8 Sentence Structures They Use


Have you caught anyone lying? Share with us in the comments below or on our Facebook page.


Edited by: The HealthWorks Team
Contributed by Dr. Leow Chee Seng

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