Skip to main content

Verified by Psychology Today

How to Detect Lies

Research examines the cognitive approach to lie detection.

Key points

  • The cognitive approach to lie detection involves asking for more information, the use of unexpected questions, and imposing cognitive load.
  • A new review study suggests the cognitive approach increases accuracy when identifying deception.
  • Signs of deception include nonverbal and verbal behaviors such as nervousness, uncertainty, and providing few details.
Source: Schwerdhoefer/Pixabay

People lie all the time; they omit information, minimize or exaggerate the truth, or give vague answers. And they lie for a variety of reasons: to save face, spare the feelings of others, get what they want, or avoid potentially disastrous consequences for themselves or others.

Yet people also value honesty. They frequently want, even demand, that others be honest with them. And they typically react negatively to dishonesty in their romantic partner, children, friends, coworkers, etc.

Research suggests dishonesty is hard to spot; there is no easy way to tell if someone is lying. Specifically, though research has identified certain verbal and nonverbal signs of lying, there are no completely reliable signs of deception. As Vrij and Easton note, “there is nothing as simple and obvious as Pinocchio’s growing nose .”

So, having established it is difficult to tell if someone is lying, the question is, Are there ways to improve lie detection? Yes, according to new findings by Giolla and Luke: The cognitive approach to lie detection may increase the accuracy of detecting deception. Their findings, published in the April issue of Applied Cognitive Psychology , will be described below.

The cognitive approach to lie detection

The cognitive approach to lie detection emphasizes several techniques, including the following three:

1. Imposing cognitive load

Cognitive load concerns the demands placed on a person’s cognitive resources (e.g., attention, memory). For instance, environmental distractions (e.g., noise) or strong emotions (e.g., extreme fear or anger) decrease the cognitive resources available to a person trying to recall the details of an event.

But lying, compared to telling the truth, also places a greater demand on one’s mental resources; therefore, when we impose a cognitive load on the individual being questioned, he or she may find it more difficult to tell a lie.

The authors note some techniques useful in increasing cognitive load include: The individual can be asked to “provide their statement in reverse order,” “perform a secondary task while providing a statement,” or “to maintain eye contact with the interviewer at all times.”

2. Encouraging the person to say more

In general, people who tell the truth can quickly provide more relevant information when asked. Liars, in contrast, will have to fabricate additional details. Therefore, liars are more likely to make mistakes and give details inconsistent with the information already provided or the verifiable facts of the event.

Some techniques used to encourage a speaker to provide more details include showing them a model statement that demonstrates the high level of detail expected in an ideal answer, requesting that the individual report everything they are able to recall (even unrelated details), and asking the individual to draw a detailed sketch of the location or event.

3. Unanticipated questions

It is assumed that when given enough time, liars prepare themselves for the interview or interrogation by anticipating the questions they will likely be asked. Such prepared lies are usually difficult to detect since they are less likely to be associated with typical deception cues.

So, one way to detect lies when the liar has had plenty of time to prepare is by asking unanticipated questions. Compared to liars, truth-tellers will answer these questions more quickly and consistently and provide more information.

The cognitive approach: Methods and results

Let us now consider the findings of the meta-analysis by Luke and Giolla. These researchers selected 23 independent samples for the quantitative synthesis; 16 included a control condition (i.e., no cognitive approach to lie detection).

In total, there were 1,781 individuals receivers , meaning participants whose job was to decide if a message was true or false. In the control conditions, there were 1,165 receivers.

The results of the meta-analysis showed the cognitive approach was associated with an (uncorrected) average accuracy rate of 60%.

One way to determine whether 60% is a good accuracy rate is by comparing it with the accuracy rate in the control conditions in this review (48%). Alternatively, we could compare it with findings from previous studies, which suggest an average accuracy rate of 54%. From this perspective, 60% accuracy is a very small improvement.

However, the authors note, if we focus on trials where the observers were told which signs of lying they should focus on (e.g., how logical and plausible a story is, how much detail is provided), the results are very different:

While the accuracy rate of people not informed of objective signs of deception is close to 50%, informed participants achieve “an average accuracy rate of approximately 75%,” suggesting the “cognitive approach to lie detection can improve accuracy rates by 21–27%.”

This makes sense. Because the goal of the cognitive approach to lie detection is to magnify certain deception cues, if a person does not pay attention to these potential signs of lying, then their ability to detect lies would not improve.

Source: PDPics/Pixabay


It is not easy to tell when someone is lying. To spot liars, people often look for signs of deception . Signs of deception include a variety of nonverbal and verbal behaviors, like nervousness and tension, giving answers with limited detail and answers that make little sense, appearing uncertain, and sounding less direct and personal.

Because lying is mentally taxing and uses up a lot of cognitive resources (attention, memory), the cognitive approach to lying suggests watching for signs of deception after introducing cognitive load should make it easier to differentiate liars from truth-tellers.

The reviewed meta-analysis, which summarized almost 16,000 veracity judgments, found the cognitive interviewing tactics did improve lie detection accuracy, but only if observers are told what deception cues to focus on. If not, the use of the cognitive approach does not offer significant advantages over unassisted lie detection.