“Truth is the most valuable thing we have. Let us economize it.” –Mark Twain
Much research has tested the reliability of various lie detection techniques. Some methods are quite effective – if you’re properly trained and if you apply these skills frequently. However, there is no lie detection “magic bullet” that works every time and with every person. There are only probabilities: Based on the person’s behavior, is it more likely than not that he or she is being truthful?
There are two problems with most on-the-fly attempts at lie detection – false positives and false negatives. In other words, you might err in accepting a false statement as true or rejecting a true statement as false. Even polygraph machines can produce false positives and negatives (the polygrapher’s skill or lack thereof also may affect the results).
To recognize deception in social or business situations, we need an approach that can be readily applied. It must minimize the risk of false positive and negatives. If not it will be worse than useless. In short we require a simple and reliable technique that can increase the probability of making accurate assessments of truthfulness or untruthfulness.
There is such a technique. It substantially increases the probability that you can separate lies from truth (and the operative word there is probability, not absolute certainty). Its main limitation is that it can only be applied in certain situations.
Suppose you are interviewing someone for a job, or on a first date, or trying to find out whether a child stole something (or knows who did). In those situations, you’re in a position to ask a series of questions. That’s when the technique I’m about to describe is most useful.
1. Begin by asking a series of innocuous questions. Preferably, you would already know the answers to these questions. But you might also ask questions which most people would not lie about: Where did you grow up? Where do you work? Do you have any children?
2. With each answer to your questions, notice which way the person’s eyes move. Eye movement is associated with which part of the brain someone is accessing to retrieve the information.
3. After you have noted “truthful” eye movement patterns, ask a question that the person may or may not want to answer truthfully: Why did your last relationship end? Why did you leave your last job? Do you know anything about the missing money? If the eyes move in a different direction, the person is probably not retrieving memories but is drawing on a different part of the brain to craft a plausible lie.
Eye movement is difficult to fake consistently even if the person is attempting to do so. The level of mental effort needed to control the eyes, tell lies, and sustain a normal conversation is too great. In the right circumstances, you can tell they’re lying not when their lips move, but when their eyes do.
Dale Hartley is associate professor and chair of the humanities, fine arts, and social sciences division at West Virginia University.
This article appeared in psychologytoday.com on 24 January 2017