3 Simple Techniques to Detect Deception
Increasing cognitive load increases the probability of deception.
Posted Sep 28, 2020
Increasing a liar’s cognitive load increases the probability of detecting deception. A truthful person simply conveys the truth, which requires little cognitive processing. Conversely, liars experience an increase in cognitive processing because liars must remember a set of made-up facts. Additionally, liars must control their verbal and nonverbal behaviors as well as monitor the verbal and nonverbal behaviors of the lie target to ensure the story is believed. During increased cognitive load, liars often leak verbal, nonverbal, and paralinguistic deceptive indicators.
Current deception studies introduce activities that add additional cognitive load to induce leakage that portend deception. Leakage is defined as any cue that the interviewee exhibits that could indicate the interviewee is being deceitful. Signs of leakage due to induced cognitive load include uncertainty, vagueness in narrative detail, response latency represented by frequent pausing, leaning backward, and leaning the head and torso away from interviewers. The following three simple techniques increase cognitive load.
Reverse event recall
The first technique is to ask a person to recall their story in reverse order. Liars tend to prepare their stories in chronicle order. They start from the beginning and order facts in a logical progression. After creating a believable story, liars typically practice their invented story countless times until they have all the facts memorized and can repeat the lie without hesitation.
Liars rarely, if ever, practice their stories in reverse order. Telling a story in reverse order is cognitively taxing. Truthful people experience little trouble telling a story in reverse order. Liars, on the other hand, need additional cognitive processing in order to repeat a story backward. Asking a suspected liar, “Please tell me what happened but start with the last thing that you remember happening,” increases cognitive load.
Liars will display speech hesitations, relate facts out of logical sequence, and become frustrated. These are the telltale signs that the person is lying.
Ask unanticipated questions
The second technique requires the interviewer to ask unanticipated questions. Unanticipated questions are questions that the liar was unable to rehearse.
Liars often prepare to answer obvious questions in the event their lie comes under scrutiny. Liars rarely prepare for questions about how they felt during the story they are trying to pass off as the truth. Liars will often struggle to accurately describe what emotions they felt because they did not actually experience the events they are relating. Since the question was unanticipated, liars must take time to think about what emotions they would have felt if they actually experienced the events they were talking about.
Speech hesitations, answering the question with a question, and the use of filler words such as ah and um increase to give the liar time to think of an appropriate answer.
Maintaining eye contact
The third technique is to request a person to maintain eye contact. Demanding eye contact increases cognitive load. Maintaining continuous eye contact with the interviewer showed significant differences between a truth-teller and a liar. The additional command to maintain eye contact, on top of lying, increases a liar’s cognitive load, supporting the theory that increasing cognitive load more accurately discriminates liars from truth-tellers.
Requesting eye contact intensifies verbal and nonverbal indicators of deception, increasing the probability of detecting deception. Parents have long used this technique to determine if their children are lying. The oft-heard demand to “Look me in the eye when you talk to me” has merit.
However, asking someone to look you directly in the eye may when they speak should be used with caution. People from some cultures may avoid eye contact as a sign of respect, this does not indicate deception. Additionally, people with certain medical conditions, especially people suffering from autism, avoid eye contact for reasons other than trying to be deceptive.
Creating a lie depletes cognitive resources. Recalling an event in reverse order, demanding eye contact, and asking unanticipated questions further denigrates cognitive processing. Requiring liars to perform two cognitively demanding activities simultaneously such as lying and recalling an event in reverse, reduces the amount of cognitive resources required to lie successfully. When less cognitive attention is devoted to lying, discrepancies, incongruences, or other deceptive indicators become more apparent.
For more techniques see The Truth Detector: An Ex-FBI Agent’s Guide for Getting People to Reveal the Truth.
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Vrij, A., Fisher, R., Mann, S., & Leal, S. (2008). A cognitive load approach to lie detection. Journal of Investigative Psychology and Offender Profiling, 5, 39-43.
Walcyzk, J. J., Igou, F. P., Dixon, A. P., & Tcholakian, T. (2013). Advancing lie detection by inducing cognitive load on liars: A review of relevant theories and techniques guided by lessons from polygraph-based approaches. Frontiers in Psychology, 4, 1-13 doi:10.3389/fpsyg.2013.00014.