Lies can also generate emotions, ranging from the excitement and pleasure of “pulling the wool over someone’s eyes”, to fear of getting caught, to feelings of guilt. Darwin first suggested that emotions tend to manifest themselves in the facial expressions, as well as in voice tones, and that these can be reliable enough to accurately identify emotional states. Research has since shown that for some expressions – e.g., anger, contempt, disgust, fear, happy, sadness/distress, or surprise –cultures throughout the planet recognize and express these emotions in both the face and voice similarly. To the extent that a lie features higher stakes for getting caught, we would expect to see more of these signs of emotion in liars compared to truth tellers. If the lie is a polite lie that people tell often and effortlessly, there would be less emotion involved. Meta-analytic studies suggest that liars do appear more nervous than truth tellers, with less facial pleasantness, higher vocal tension, higher vocal pitch, greater pupil dilation and fidgeting. If the lie itself is about emotions – e.g., telling someone that one feels calm, when in fact one is nervous – the research shows that signs of the truly felt emotion appear in the face and voice despite attempts to conceal, although these signs are often subtle and brief.
The face is the primary vehicle for expressing emotions. Although researchers agree for that most types of facial expressions shown by people are consciously displayed, learned like language, and their meanings are culturally specific that rely on context for proper interpretation, e.g., a wink, or a raised eyebrow signaling skepticism, a subset of distinct facial expressions appear to be manifestations of emotional states in all human beings, often unconsciously displayed, biologically wired, and whose meanings are similar across all cultures. This idea was originally proposed by Darwin, and later elaborated by others to posit that social animals, such as humans, must communicate these emotions to others in the group because emotions express imminent behavior, such as striking out in anger, fleeing in fear, and other action tendencies. For example, humans express the emotion of happiness by raising their lip corners and contracting the muscle that circles the eye. Humans express sadness by lowering their lip corners and pulling their inner eyebrows upward. Other emotions besides happiness and sadness that seem to have specific facial expressions include anger, disgust, fear, and surprise, and to a lesser extent contempt, embarrassment, interest, pain, and shame. There is compelling evidence that these emotions are expressed and interpreted the same across all cultures. This “universal” production and perception across cultures suggests that those emotions and their specific facial expressions are genetically determined, rather than socially learned. A number of studies have documented the relationship between these facial expressions of emotion and the physiology of the emotional response. Indeed a review on the psychology of emotion concludes that the empirical evidence shows that the more protypical the emotion eliciting event is to those faced by our ancient ancestors, the stronger the link between the facial expression and the physiology – which leads to the unambiguous conclusion that a facial expression is a significant part of the emotional response.
These facial expressions of emotion can be very useful for identification of deception. In situations in which individuals are motivated to conceal their fear of getting caught, or their distress at being evaluated, their facial expressions may ‘leak’ despite their efforts to conceal them. Our current work has found that we can successfully classify liars and truth tellers at around 70% accuracy based solely on their facial expressions, and that many of these expressions are micro-momentary, or what Ekman called a “micro expression”. They last for less than 1⁄2 a second, are reported by the liars to be successfully concealed and are typically not seen by untrained observers. This result has not been prominent in the literature outside of our research team because to date no researchers have employed the same level of detailed analysis as we have; that is, we have used Ekman & Friesen’s Facial Action Coding System (1978), an objective system for scoring all visible facial muscle movement, not just that related to emotion or deception. This is laborious, frame by frame work but has revealed these previously unseen actions. A review of the status of nonverbal behavior sponsored by the Defense Intelligence Science board concluded that this approach examining facial action units has shown promise. The theoretical/physiological reason these expressions can be micro-momentary is that they occur at the confluence of two neuroanatomical expressive systems. Neuroanatomical research demonstrates that facial expressions can be both biologically driven, as in the case of the emotions, and socially learned, as in the case of all other posed facial expressions. There appears to be two distinct neural pathways that mediate facial expressions, each one originating in a different area of the brain. The pyramidal motor system drives the voluntary facial actions, and originates in the cortical motor strip; whereas the extrapyramidal motor system drives the more involuntary, emotional facial actions, and originates in the subcortical areas of the brain. The research documenting these differences is reliable enough that prior to modern methods that see through tissue, they served as the primary diagnostic criteria for certain brain lesions. In this literature one can see photos of a man with a brain tumor on his cortical motor strip that shows hemi-paralysis when he is asked to pose a smile, yet this same man shows a beautiful full bilateral smile when he is told a joke – thus proof that there must be two pathways to the face.