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Lie detection

Dr. Simon Moss


Many techniques and approaches have been developed to determine whether someone is lying. Unfortunately, no single cue, such as protracted pauses before an answer, always indicate that a person is fabricating an account.

Nevertheless, depending on the precise context, individuals will tend to exhibit specific clusters of cues when they lie. To illustrate, if they are concerned they might be detected, they will often inhibit any movement in their hands and fingers. Similarly, if the other person seems suspicious, the pitch of their voice might rise.

Cues that indicate deception

Features of eyes

A meta-analysis showed that rate of blinking does not relate to lying (DePaulo, Lindsay, Malone, Muhlenbruck, Charlton, & Cooper, 2003). As Leal and Vrij (2008) showed, however, the association between rate of blinking and lying may be complex. That is, while individuals lie, the rate at which their eyes blink tends to diminish. After the lie is completed, they tend to blink more frequently--even more frequently than usual. The slow rate while lying tends to coincide with concentration. The rapid rate after lying might coincide with anxiety, perhaps related to the worry the fabrication might be detected.

Furthermore, when individuals lie, their pupils are also more likely to dilate (for a meta-analysis, see DePaulo, Lindsay, Malone, Muhlenbruck, Charlton, & Cooper, 2003). Conceivably, this dilation could indicate arousal and anxiety. Alternatively, this dilation could represent concentration and attention. Indeed, both arousal and working memory tend to coincide with pupil dilation (Beatty & Lucero-Wagoner, 2000).

Speech errors

When individuals lie, their speech is more likely to include errors. They will, for example, sometimes include hesitations, like "um"s (Vrij, Edward, & Bull, 2001). Their grammar might also be incorrect. They might repeat themselves or retract their statements (see Feeley & deTurck, 1998). Interruptions during sentence are also common (Anolli & Ciceri, 1997).

These errors could indicate the person is concentrating on fabricating the account rather than speaking grammatically. Consistent with this possibility, when individuals are particularly motivated to conceal their deception, these errors are especially prevalent (for evidence, see the meta-analysis conducted by Sporer & Schwandt, 2006& for conflicting evidence, see Feeley & deTurck, 1998).

Furthermore, when individuals lie, they are more likely to repeat themselves (DePaulo, Lindsay, Malone, Muhlenbruck, Charlton, & Cooper, 2003). They may repeat words or phrases, even within the same sentence. Alternatively, they might repeat an entire detail or argument.

Although they often commit speech errors, individuals who lie are often unwilling to concede mistakes (DePaulo, Lindsay, Malone, Muhlenbruck, Charlton, & Cooper, 2003). Relative to people who convey a true account, people who convey a false account are not as likely to retract a previous remark. They are also unlikely to concede they cannot remember a detail.


In some circumstances, deceptive individuals will behave more cooperatively, to seem honest and authentic. To illustrate, after some incident, like a theft, the suspects are often instructed to describe their whereabouts, sometimes several times. Many suspects will refuse this request. Nevertheless, the individuals who are indeed culpable are more inclined to justify this refusal more cooperatively and convincingly. In particular, these individuals are especially motivated to appear sincere and reasonable, as confirmed by Vrij (2004).

Causes of cues that indicate deception

Detailed representations of actual events

When individuals experience an event, they will tend to store this episode in memory, along with a host of details, such as the time of year as well as the sights, smells, and sounds in the surroundings. In contrast, when individuals fabricate an event, they strive to ensure the sequence of events is logical. They do not focus on details of the context. Therefore, when they describe this fabricated event later, their accounts are often devoid of certain details or references to the context (e.g., Vrij, Edward, Roberts, & Bull, 2000).

Vrij, Edward, Roberts, and Bull (2000) validated this possibility. In this study, participants presented either a genuine anecdote or a fabricated account. The fabricated accounts alluded to fewer details in the environment. Sounds, smells, and other stimuli were seldom mentioned (see also Vrij, Edward, & Bull, 2001).

Attempts to conceal cues and appear convincing

Some of the cues that coincide with lying represent an attempt in individuals to conceal their insincerity. That is, throughout evolution, many animals, especially humans, have developed the capacity to mislead rivals. However, to fulfill this goal effectively, they need to be ensure their insincerity is not recognized. That is, they need to conceal gestures, expressions, or vocal characteristics that might expose this deception.

This inclination, presumably, evolved in humans as well. That is, humans have evolved to conceal some of the cues or mannerisms that would reveal their insincerity (Vrij, 1994). For example, when some humans lie, they become especially disinclined to move their hands or fingers as they speak. Presumably, this immobility evolved as an attempt to conceal the cues that could reveal dishonesty.

Vrij, Akehurst, and Morris (1997) undertook studies that support this account. In this study, participants were asked to either lie or speak truthfully. The hand and finger movements of these participants were monitored. Furthermore, the degree to which individuals felt motivated to depict themselves favorably was also assessed, using a scale called public self-consciousness.

As hypothesized, individuals were not as inclined to move their hands and fingers when lying. They were not as likely to point, for example (see also Caso, Gnisci, Vrij, & Mann, 2005). Furthermore, this tendency to stifle hand and finger movements was especially pronounced in participants who like to depict themselves favorably. These findings, therefore, indicate that limited hand and finger movement might represent an attempt to conceal insincerity and maintain a positive reputation (for further evidence, see Vrij, Edward, & Bull, 2001& Vrij, Edward, Roberts, & Bull, 2000).

Nevertheless, when individuals lie, some hand movements are more frequent. To illustrate, as Caso, Maricchiolo, Bonaiuto, Vrij, and Mann (2006) showed, when individuals fabricate an account, they are more likely to illustrate or explain their remarks with gestures. They might form shapes with their hands that correspond to an object or concept they are describing. They might wave their hands to symbolize complexity, and so forth.

In addition, when individuals lie, their responses to questions are often shorter (for evidence, see the meta-analysis conducted by Sporer & Schwandt, 2006). These short answers might also represent an attempt to curb the likelihood of exhibiting cues that indicate deception. Alternatively, these short answers might arise because the memory representations of fabricated accounts include fewer contextual details.

Some cues, however, cannot be concealed as readily. For example, even when individuals strive to conceal their lies, the pitch of their voice remains elevated--a sign of anxiety and arousal (Sporer & Schwandt, 2006). Indeed, even when people are told to stifle these tendencies or mannerisms and thus conceal their deceit, these signs of deception are still displayed (Caso, Vrij, Mann, & DeLeo, 2006). The term leakage is often applied to describe this inability to control all cues.


As Vrij, Edward, and Bull (2001) emphasized, many of the cues that coincide with deception tend to reflect increases in concentration. That is, to lie effectively, individuals need to remember the details they shared. They also need to ensure the events seem plausible and consistent with one another. Furthermore, they need to be creative. These objectives demand concentration and effort.

Because of this concentration and effort, deception will sometimes coincide with particular cues. For example, as Vrij, Edward, and Bull (2001) showed, when individuals fabricate an answer to a question, they are more likely to pause before replying (for further evidence, see the meta-analysis conducted by Sporer & Schwandt, 2006). That is, if individuals lie rather than speak truthfully, the delay before an answer is usually extended. These pauses might reflect the need to reflect carefully before articulating a response.

Anxiety and arousal

As many researchers such as Anolli and Ciceri (1997) have shown, when individuals lie, they sometimes manifest signs of anxiety and arousal. For example, the pitch of their voice tends to rise. Furthermore, if individuals feel anxious, they are also not as likely to pause before their answers.

Indeed, the association between anxiety and lying motivated the advent of polygraphs. Typically, individuals receive either questions relating to the crime or questions relating to some other unsettling issue. Guilty perpetrators tend to show more anxiety, as measured by various physiological indices, in response to the questions that relate to the crime, whereas innocent individuals tend to show more anxiety in response to the questions that relate to other unsettling issues. Alternatively, individuals receive questions about knowledge of which only a guilty person would be aware.

In addition to physiological indices, anxiety and arousal often manifests as microexpressions: rapid mannerisms that are difficult to control. These microexpressions include fleeting shifts in the tone of voice, transient shaking of the head, and brief negative facial expressions. As Frank and Ekman (1997) showed, these microexpressions are more common when individuals lie. Furthermore, if listeners strive to orient their attention to these microexpressions, they can more readily ascertain whether or not someone is lying.

Factors that determine which mechanism prevails

When individuals lie, they can manifest a range of cues. Some of these cues reflect attempts to prevent any signals they might be lying. Other cues are evoked when individuals concentrate diligently, striving to maintain a coherent and compelling account. In addition, some cues coincide with anxiety and arousal. In short, the various cues reflect distinct mechanisms or causes.

Nevertheless, the cues that correspond to one mechanism sometimes conflict with the cues that correspond to another mechanisms. When individuals concentrate, for example, they often pause before answers. When individuals feel anxious, they are disinclined to pause. Whether or not individuals pause or manifest other cues will, therefore, depend on which of these mechanisms prevail.

Effects of suspicion

To illustrate, as Anolli and Ciceri (1997) showed, when individuals do not feel the other person is suspicious, the effect of concentration override the effects of anxiety. These individuals will often pause or hesitate as they fabricate their answers. When individuals feel the other person is suspicious, however, the effect of anxiety prevails. Individuals will seldom pause before they fabricate their answers: Their replies tend to be prompt instead.

Similarly, suspicion also evokes particular gestures. Although lying tends to curb pointing, suspicion actually increases the likelihood of pointing (e.g., Caso, Gnisci, Vrij, & Mann, 2005). Suspicion also increases the incidence of rhythmic gestures (Caso, Gnisci, Vrij, & Mann, 2005).

Preparation of lies

Furthermore, when the lies are prepared, the effect of attempts to conceal deception override the effects of anxiety. That is, anxiety dissipates whenever the fabrications are prepared. Consistent with this premise, if the lies are prepared in advance, the voice does not rise appreciably (Sporer & Schwandt, 2006).

Approaches that have been designed to uncover deception

The timed antagonistic response alethiometer

Gregg (2007) developed a technique called the timed antagonistic response alethiometer. In essence, individuals receive a set of factual statements, such as "Grass is green", and personal statements, such as "I have stolen money from my company before". They are instructed to press one button, such as the Q key, if the statements are correct and another button, such as the P key, if the statements are incorrect. Individuals who lie about some of the personal statements tend to respond especially slowly.

To demonstrate, suppose they receive the personal question "I have stolen money from my company before" and want to conceal this event by lying. They would need to press the P key to pretend this statement is false, even though they need to press the Q key when other statements are correct. Hence, they need to change their strategy when these personal statements are presented, which delays their response. Gregg (2007) offered some preliminary evidence to validate this technique provisionally.

Questioning techniques

One obvious but effective technique, validated by Vrij, Leal, Granhag, Mann, Fisher, Hillman, and Sperry (2009), is to ask pairs of suspects unanticipated or unusual questions. In one study, for example, pairs of individuals were asked to describe a lunch they shared together. Some of these pairs were instructed to lie, whereas other pairs were instructed to speak truthfully.

Some of the questions were anticipated--questions about the sequence of events, for example. Other questions, especially about the spatial arrangement of people and tables, were unanticipated. When unanticipated questions were asked, judges could often distinguish between deceptive and truthful pairs. Correct classifications approached 80%.

Vrij (2006) also argued that interviewers should gather additional information after interrogating people to detect dishonesty. That is, according to Vrij (2006), after individuals are interrogated, they become especially motivated to conceal their lies. Because of this motivation, they attempt to obscure or control any cues that could expose their deception. Their behavior seems very inhibited: Their hands and fingers do not move, for example. Hence, deception can be more readily detected.

Specifically, during an interrogation, the claims of individuals are challenged, and suspicions are raised. The individuals, therefore, feel they are being scrutinized carefully. They subsequently feel the need to conceal their deception even more intensely than before. Consequently, they stifle their mannerisms, manifesting as stiff and stilted behavior.

Vrij (2006) validated this technique. Individuals were told to lie or speak truthfully. They were then exposed to three phrases of questions. The first phase was designed to gather information about an event. The second phase was an interrogation, in which the participants were challenged more forcefully. The third phase was also designed to gather information. During the third phase, the judges could more readily distinguish the fabricated and genuine accounts. The people who lied seemed more inhibited in their mannerisms.

Vrij, Fisher, Mann, and Leal (2006) also argued that individuals should not only modify their overt questions but should also modify their questions to themselves. Rather than ask themselves whether the person is lying, they should ask themselves whether the person seems to be thinking intensely--a possible manifestation of fabrications. When they ask themselves whether the person seems to be thinking intensely, they naturally orient their attention to suitable cues, such as limited hand movements.

Training in lie detection

Sometimes, to enhance their capacity to detect fabrications, individuals participate in training programs. They might learn about the facial expressions, mannerisms, words, or phrases to which they should direct their attention.

Although sometimes effective, training can also compromise the capacity of individuals to detect lies. In one study, conducted by Akehurst, Bull, Vrij, and Kohnken (2004), the participants were police officers, social workers, and students. They were asked to rate the veracity of four verbal transcripts, both before and after training in Criteria Based Content Analysis.

Specifically, during this training, participants learnt about the properties of content that might indicate deception. They learn, for example, to ascertain whether individuals were able to describe the context or surroundings, reproduce some of the conversation, allude to unusual or superfluous details, refer to their own mental state, admit to uncertainty or errors, and so forth--all of which tend to indicate honesty.

Before this training, police officers, social workers, and students did not significantly differ from one another in their capacity to detect deception from written testimonies. After training, the social workers outperformed the other samples. Indeed, the police officers actually deteriorated. Conceivably, this application of principles overrides their natural intuition.

Methodology of studies

Many methods have been utilized to examine the cues that coincide with deception. In a typical study, individuals are asked to engage in some inappropriate act. In the experiment that was reported by Vrij, Akehurst, and Morris (1997), for example, individuals were told to hide a set of head phones. Later, another person asked these participants about the whereabouts of these headphones.

Some participants had previously been instructed to lie--to maintain they had not concealed the headphones. Other participants had previously been instructed to respond truthfully. The participants were videotaped while they responded to these questions.

Similarly, in the study conducted by Vrij, Akehurst, Soukara, and Bull (2004), participants erased some material from a blackboard. Later, they were instructed to either deny or admit to this event. Again, characteristics of their speech and mannerisms were assessed.


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