Researchers have examined a variety of different non-verbal behaviours, including gaze aversion (looking away from the conversation partner), smiling, illustrators (hand and arm movements that accompany speech and illustrate it), self-manipulations (touching or scratching body or face, playing with own hair, playing with objects), subtle movements of hands and fingers, speech rate, pauses in speech, speech latency (period between question being asked and answer being given), speech fillers (um's and er's), stutters (repetitions of words, correcting sentences, and so on), and pitch of voice. Vrij (2000) reviewed more than 40 studies concerning such behavioural indicators of deception. The review revealed that deception is not related to a unique pattern of specific behaviours. In other words, there is nothing like Pinocchio's nose. Some behaviours, however, are more likely to occur during deception than others. Liars tend to speak with a higher-pitched voice, speak slower, pause longer while they speak, and display a decrease in illustrators, hand/finger movements, and leg and foot movements (Vrij, 2000).
Three theoretical approaches are usually offered to explain these findings: the emotional approach, the cognitive approach, and the attempted control approach (Burgoon et al., 1989; DePaulo, 1988, 1992; DePaulo and Kirkendol, 1989; DePaulo, Stone andLassiter, 1985a; Ekman, 1989,1992; Ekman and Friesen, 1972; Goldman-Eisler, 1968; Knapp, Hart and Dennis, 1974; Kohnken, 1989, 1990; Riggio and Friedman, 1983; Vrij, 1998, 2000; Zuckerman, DePaulo and Rosenthal, 1981). Although deception in itself does not lead to specific behaviour, liars may experience emotional, content complexity, and controlling processes, which may influence their behaviour. Each process emphasises a different aspect of deception and deceptive behaviour. However, the distinction between them is artificial. Lies may well feature all three aspects, and the three approaches should not be considered as different camps.
The emotional approach proposes that deception can result in various emotions. The three most common types of emotion associated with deceit are guilt, fear and excitement (Ekman, 1992). People may feel guilty while lying, because they realise that it is morally wrong to deceive; they might also be afraid, because they might be worried that someone will find out that they are lying; they might become very excited because they might enjoy the opportunity to fool someone. The strength of these emotions depends on the personality of the liar and on the circumstances in which the lie takes place (Ekman, 1992; Vrij, 2000). The higher-pitched voice during deception might be the result of the emotions that liars experience (Ekman, Friesen and Scherer, 1976). However, differences in pitch between liars and truth tellers are usually very small, only a few Hertz, and therefore usually only detectable with sophisticated equipment.
The content complexity approach emphasises that lying can be a cognitively complex task (Vrij, 2000). Liars have to think of plausible answers, should not contradict themselves, should tell a lie that is consistent with everything which the observer knows or might find out, and should avoid making slips of the tongue. Moreover, they have to remember what they have said, so that they can say the same things when someone asks them to repeat their story. People engaged in cognitively complex tasks speak slower and pause more (Goldman-Eisler, 1968). Cognitive complexity also leads to fewer movements, due to the fact that a greater cognitive load results in a neglect of body language, reducing overall animation (Ekman and Friesen, 1972).
So far, the predictions of how liars behave have been straightforward. A liar may experience emotions or may find it difficult to lie, and this will result in behaviourial signs of emotion and content complexity. However, the situation is more complicated than this. Liars may be afraid that several cues will give their lies away, and therefore try to suppress such signs in order to avoid getting caught. This is emphasised in the attempted behavioural control approach (Vrij, 2000). Hocking and Leathers (1980) argued that liars' attempts to control their behaviour will focus on those behaviours that fit the cultural stereotype of liars. For example, if there is a widespread belief that liars look away, increase their movements and stutter, then liars will try to maintain eye contact, refrain from making too many movements, and will try to speak smoothly. When people try to do this, they sometimes tend to overcontrol themselves, which results in behaviour that looks too rehearsed and too rigid (i.e. decrease in movements) (Vrij, 2000).
Vrij's (2000) literature review showed a conflicting pattern concerning speech fillers and stutters. In most studies an increase in speech fillers and stutters were found, but some studies revealed the opposite pattern (a decrease in speech fillers and stutters). Vrij and Heaven (1999) found in their study that variations of lie complexity are responsible for these conflicting findings. When the lie was easy to fabricate, a decrease in speech errors and stutters occurred, whereas the opposite pattern occurred when the lie was difficult to fabricate. Vrij and Heaven (1999) suggested that, in line with the attempted behavioural control approach, liars will try to avoid making speech errors and stutters while lying. However, they only achieve this when the lie is easy to formulate. When the lie is difficult to fabricate an increase in speech errors and stutters occurs, due to the cognitive load required to fabricate the lie.
Perhaps the most interesting aspect of the literature review was the absence of several signs of nervousness as indicators of deception. For example, nervous behaviours such as gaze aversion and fidgeting are not related to deception (see also DePaulo et al., 2000). This is remarkable as most people, often including professional lie detectors such as the police and customs officers, believe that liars fidget and look away (Akehurst et al., 1996; Vrij and Mann, 2001a; Vrij and Semin, 1996).
One possible reason why liars don't show clear patterns of nervous behaviour is that the stakes (the positive and negative consequences of getting caught) are not high enough for the liar in (most of the) deception studies to elicit clear nonverbal cues to deception (Mann, Vrij and Bull, 2002; Miller and Stiff, 1993; Vrij, 2000). The vast majority of deception studies are experimental studies: laboratory studies in which participants (usually university students) are requested to lie or tell the truth for the sake of the experiment. The research designs typically involve asking a participant to lie about various issues. People lied or told the truth about beliefs and opinions (DePaulo and Rosenthal, 1979; DePaulo, Stone and Lassiter, 1985b), about personal facts such as the course they study (Vrij and Holland, 1998), about videofilms or pictures they had just seen (Bell and DePaulo, 1996; Ekman and Friesen, 1974; Vrij and Heaven, 1999), about feelings about an object or person (DePaulo, Lanier and Davis, 1983;DePaulo, LeMay and Epstein, 1991;DePaulo, Stone and Lassiter, 1985b; Ekman and Friesen, 1974; Frank and Ekman, 1997; Riggio, Tucker and Throckmorton, 1988), or about the possession of an object (Vrij, 1995; Vrij, Akehurst and Morris, 1997). Also, people were induced to cheat and then to lie about it (deTurck and Miller, 1985), or were given the opportunity to take money and, if taken, to lie about this in a subsequent interview (Frank and Ekman, 1997).
In order to raise the stakes in laboratory experiments, participants are offered money if they successfully get away with their lies (Vrij, 1995), or researchers tell participants (nursing students) that being a good liar is an important indicator of being successful in a future career (Vrij, Edward and Bull, 2001a, c).2 In some studies, participants are told that they would be observed by a peer who will judge their sincerity (DePaulo, Stone and Lassiter, 1985b). Obviously, the stakes in these experimental studies are still lower than the stakes in several real-life situations. Frank and Ekman (1997) therefore raised the stakes even further. In their study, participants were given the opportunity to take 50 dollars. If they could convince the interviewer that they had not taken the money, they could keep the 50 dollars. If they took the money and the interviewer judged them as lying, they had to give the 50 dollars back and also lost their 10 dollars per hour participation fee. Moreover, some participants faced an additional punishment while lying. They were told that they would have to sit on a cold, metal chair inside a cramped, darkened room labelled ominously XXX, where they would have to endure anywhere from 10 to 40 randomly sequenced, 110-decibel starting blasts of white noise over the course of one hour. These participants were given a sample of this punishment prior to engaging in the task. However, no participant who was judged lying actually received the punishment (Frank and Ekman,
2 This information is based on evidence. Ekman and Friesen (1974) have found that nurses' ability to conceal negative emotions (when they interact with patients who are terminally ill, or with patients with severe burns, and so on) is very useful in their jobs.
1997, pp. 1431/1432). Although this laboratory study might be a good example of a high stake study, it also raises serious ethical concerns. To what extent is it ethically acceptable to threaten people so much, just for the sake of an experiment? See Vrij (2002b) for a discussion concerning ethical issues in deception research.
Whatever researchers try, the best insight into deceptive behaviour in real-life situations will be obtained by examining people's behaviour in such situations. This is exactly what some researchers recently did (Davis and Hadiks, 1995; Vrij and Mann, 2001b; Mannetal., 2002). For example, Vrij and Mann (2001b) examined videotapes of a murderer when he was questioned by the police regarding his crime. The man initially denied having committed the crime, but confessed following the presentation of indisputable evidence. Davis and Hadiks (1995) analysed Saddam Hussein's behaviour while he was interviewed by CNN during the Gulf War. Interestingly, the murderer in Vrij and Mann's study did not show a clear pattern of nervous behaviours, neither did Saddam Hussein while he lied during his CNN interview. An explanation why nervous behaviours might still not be present in high-stakes lie situations is that liars probably will experience increased cognitive load and/or attempted behavioral control, which will negate their nervous behaviours. In the most extensive study examining the behaviour of authentic high-stake liars to date, Mann et al. (in submission) analysed, amongst others, the behaviour of 13 male suspects during their police interviews. The strongest indicator for deceit in that study was eye blinking, with 11 out of the 13 male suspects (85%) showing less eye blinking while lying. This is an interesting finding since research on eyeblinks has shown that these decrease as a result of cognitive load (Bagley and Manelis, 1979; Bauer et al., 1985; Wallbott and Scherer, 1991), but increase as a result of stress (Harrigan and O'Connell, 1996; Tecce, 1992). In other words, our finding suggests that these suspects experienced more cognitive load than stress during their interviews. However, since we did not directly test this hypothesis, this conclusion should be drawn with caution.
In summary, the authentic high-stakes studies conducted so far do not support the idea that liars show nervous behaviours. Instead, liars tend to show behaviours which indicate cognitive load or attempted behavioural control. However, we have to be careful with drawing this conclusion. The studies examining behaviour during authentic high-stakes lies have only examined behaviours shown by criminals (and Saddam Hussein). Obviously, there is a difference between this sample of participants and the population at large, limiting the generalisability of the findings. For example, it might be that the people examined in these studies experienced less guilt or fear, might have been more experienced liars, or might care less about the consequences than other people (such as victims and witnesses) who are involved in high-stakes lie situations.
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This book discusses the futility of curing stammering by common means. It traces various attempts at curing stammering in the past and how wasteful these attempt were, until he discovered a simple program to cure it. The book presents the life of Benjamin Nathaniel Bogue and his struggles with the handicap. Bogue devotes a great deal of text to explain the handicap of stammering, its effects on the body and psychology of the sufferer, and its cure.