Gaze aversion. Sweaty palms. Nervous speech. Grooming gestures.
Many lay people, and even trained professionals, believe that these nonverbal cues are tell-tale signs of deceit. Yet discerning whether someone is lying to you or not is an extraordinarily difficult task. A meta-analysis of over 120 scientific studies reveal that behavioral differences between truth-tellers and liars are few, weak, and unreliable. In fact, those who believe they are “expert lie detectors” (e.g., police officers, judges, prosecutors, immigration officers) achieve only about 54% accuracy (thus, not much better than flipping a coin or 50% chance). Despite this mounting scientific evidence, behavioral cues are still heavily relied on as indicators of truthfulness and deception within the law enforcement and intelligence communities. The gold standard of lie detecting is the age-old polygraph. However, like microexpressions, thermal imaging and voice stress analysis, the polygraph measures nonspecific, peripheral emotional/autonomic arousal that might or might not be associated with lying.
In contrast to these emotion-based approaches to deception detection, recent research has focused on the development of cognition-based model to elicit cues to deception and truth. This approach leverages the fact that cognitive processes differ between liars and truth-tellers. One such cognitionbased strategy is “inducing cognitive load” to increase cues to deception exhibited by liars. This strategy is effective because lying is quite a complex mental process that requires much more cognitive resources (i.e., working memory and attentional resources). One way to increase cognitive load is to ask the subject to repeat their narrative in reverse order – that is, start with the last event and work backwards. This is difficult because memories are usually coded in a forward order sequence of events. Another is asking unanticipated questions, which increases cognitive load because it disrupts the scripted responses that liars rehearse in anticipation of being questioned. Lastly, one might ask a subject to maintain eye contact with the interviewer. This is difficult because people are inclined to look away in a conversation when trying to recall a memory.
In addition to these strategic questioning strategies, several veracity assessment methods have been developed that rely specifically on the content of a statement, such as the Forensic Statement Analysis (FSA) and Criteria-Based Content Analysis (CBCA). In general, these methods show that we should analyze one’s verbal content instead of solely relying on nonverbal behavior.
The science increasingly points to a cognition-based model, as opposed to the traditional anxiety-based approach, to detecting deception (71% accuracy in truth and lie detection combined).
Unfortunately, the widespread belief still remains that attending to behavioral cues alone is sufficient.
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