Nonverbal Cues

Mental State of the Liar

Initial research into the nonverbal cues of deception was concerned with the notion that liars experience different emotional states than truth-tellers. Despite liars' best efforts, unintentional manifestations of emotions were thought be observable in bodily behavior, often referred to as leakage cues. These cues are thought to reflect guilt associated with misleading another and anxiety about being caught. The leakage hierarchy hypothesis suggests that cues associated with these emotions are more likely to be expressed through bodily channels that are not as perceptually salient to a communication partner and thus not as closely monitored by the liar. As a result, leakage should be most evident in the movements of the legs and feet, followed by the hands, and less so in the more visible and practiced movements of the face. A critical [Page 721]exception, according to Paul Ekman, a pioneer of the emotional approach to lie detection, are the fleeting and nearly indistinguishable emotional expressions that occur on the face while one attempts to suppress true responses. Commonly referred to as microexpressions, the evidence for their existence has been mixed, and even when isolated, they are often reported as being too scant for reliable use in practice. Other emotional displays have been found to be more reliable indicators. For example, liars tend to produce fewer genuine smiles than truth-tellers but attempt to compensate with feigned smiles.

Extending the emotional approach, the four-factor model proposes that liars must also contend with unique cognitive demands (along with greater overall arousal and the overcontrol of behavior). In many cases, deception has been shown to be more cognitively challenging than truth-telling: a false reality must be maintained while the ever-present truth competes for expression. Thus, when cognitive demands are present during deception, characteristic signs of cognitive load are revealed across a range of nonverbal behaviors, including decreased eye blink rates, greater speech hesitations, and a longer initial pause before beginning to respond. Recently, researchers have focused more sharply on establishing nonverbal cues to deceit that tap into the heavy processing demands, with less attention given to the nonverbal behaviors indicative of felt emotions. However, it is noteworthy that there is some controversy around the cognitive load approach, with some researchers arguing that the cues to deception should be expected to decrease when a person is mentally taxed.

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