Pitfalls and Opportunities in Nonverbal and Verbal Lie Detection.

The question of whether discernible differences exist between liars and truth tellers has interested professional lie detectors and laypersons for centuries. In this article we discuss whether people can detect lies when observing someone’s nonverbal behavior or analyzing someone’s speech. An article about detecting lies by observing nonverbal and verbal cues is overdue. Scientific journals regularly publish overviews of research articles regarding nonverbal and verbal cues to deception, but they offer no explicit guidance about what lie detectors should do and should avoid doing to catch liars. We will present such guidance in the present article. The article consists of two parts. The first section focuses on pitfalls to avoid and outlines the major factors that lead to failures in catching liars. Sixteen reasons are clustered into three categories: (a) a lack of motivation to detect lies (because accepting a fabrication might sometimes be more tolerable or pleasant than understanding the truth), (b) difficulties associated with lie detection, and (c) common errors made by lie detectors. We will argue that the absence of nonverbal and verbal cues uniquely related to deceit (akin Pinocchio’s growing nose), the existence of typically small differences between truth tellers and liars, and the fact that liars actively try to appear credible contribute to making lie detection a difficult task. Other factors that add to difficulty is that lies are often embedded in truths, that lie detectors often do not receive adequate feedback about their judgments and therefore cannot learn from their mistakes, and that some methods to detect lies violate conversation rules and are therefore difficult to apply in real life. The final factor to be discussed in this category is that some people are just very good liars. The common errors lie detectors make that we have identified are examining the wrong cues (in part, because professionals are taught these wrong cues); placing too great an emphasis on nonverbal cues (in part, because training encourages such emphasis); tending to too-readily interpret certain behaviors, particularly signs of nervousness, as diagnostic of deception; placing too great an emphasis on simplistic rules of thumb; and neglecting interand intrapersonal differences. We also discuss two final errors: that many interview strategies advocated by police manuals can impair lie detection, and that professionals tend to overestimate their ability to detect deceit. The second section of this article discusses opportunities for maximizing one’s chances of detecting lies and elaborates strategies for improving one’s lie-detection skills. Within this section, we first provide five recommendations for avoiding the common errors in detecting lies that we identified earlier in the article. Next, we discuss a relatively recent wave of innovative lie-detection research that goes one step further and introduces novel interview styles aimed at eliciting and enhancing verbal and nonverbal differences between liars and truth tellers by exploiting their different psychological states. In this part of the article, we encourage lie detectors to use an information-gathering approach rather than an accusatory approach and to ask liars questions that they have not anticipated. We also encourage lie detectors to ask temporal questions—questions related to the particular time the interviewee claims to have been at a certain location—when a scripted answer (e.g., ‘‘I went to the gym’’) is expected. For attempts to detect lying about opinions, we introduce the devil’s advocate approach, in which investigators first ask interviewees to argue in favor of their personal view and then ask them to argue against their personal view. The technique is based on the principle that it is easier for people to come up with arguments in favor than against their personal view. For situations in which investigators possess potentially incriminating information about a suspect, the ‘‘strategic use of evidence’’ technique is introduced. In this technique, interviewees are encouraged to discuss their activities, including those related to the incriminating information, while being unaware that the interviewer possesses this information. The final technique we discuss is the ‘‘imposing cognitive load’’ approach. Here, the assumption is that lying is often more difficult than truth telling. Investigators could increase the differences in cognitive load that truth