This Blog reviews nonverbal, verbal and physiological cues to deception. In particular, we will discuss how liars behave, what they say, how they physiologically react and how good professional lie detectors (police detectives, polygraph examiners and so on) are at detecting truths and lies while paying attention to such cues. The chapter reveals that professional lie catchers, among others, are to some extent able to detect lies by examining behavior, speech content or physiological reactions. However, as this chapter will also show, no perfect lie detection test exists, and lie detection experts make wrong judgments on a regular basis. We will discuss several problems and pitfalls lie detectors typically face, but we start with some background information, such as a definition of deception, the types of lie people tell, the reasons why people lie and how frequently people tell lies. SOME CHARACTERISTICS OF DECEPTION Definition of Deception Elsewhere we defined deception as ‘‘a successful or unsuccessful deliberate attempt, without forewarning, to create in another a belief which the communicator considers to be untrue’’ . Some elements of this definition are worth mentioning. First, lying (we will use the words ‘‘lying’’ and ‘‘deception’’ interchangeably) is an intentional act. Someone who does not tell the truth by mistake is not lying. A woman who mistakenly believes that she was sexually abused in her childhood and reports this to the police, has given a false report but is not lying . Moreover, sometimes two witnesses give different accounts of the event they have witnessed. This does not necessarily mean that one of the two witnesses is lying. It might well be that (at least) one witness misremembers the event. second, people are lying only when they do not inform others in advance about their intentions to lie (Ekman, 1992). Magicians are therefore not lying during their performance, as people in the audience expect to be deceived. Third, a lie has been defined solely from the perspective of the deceiver. That is, a statement is a lie if deceivers believe what they say is untrue, regardless of whether the statement is actually false. Strictly speaking, even an actual truth could be a lie. Suppose that a child and his friend have eaten all the biscuits in the open pack and, unknown to the mother, have also eaten those in the pack from the cupboard. When he asks for a new pack to be opened, his mother, in an effort to prevent him from eating too much, tells him that he cannot have more because there are no packs left in the cupboard. This truthful statement is a lie as long as the mother believes that there is a pack left. Fourth, people sometimes fool themselves, a process which is called self-deception. People can ignore or deny the seriousness of several bodily symptoms, such as a severe pain in the chestduring physical exertion. According to the definition, deception is an act which involves at least two people. This definition therefore excludes self-deception.
This Blog, Psychology and Law, provides a comprehensive review of relevant topics as far as determining the accuracy of a witness, victim or suspect is concerned. Each Post not only focuses on relevant research but also presents readers with a detailed understanding of the research methodology, the theoretical perspectives, the shortcomings of the research theory and the practical significance of the findings.
