Detecting Deception: Facial Expressions and Micro-Expressions

Introduction to Deception Detection

Psychology professor Paul Ekman pioneered the use of facial expression recognition for the purpose of detecting deliberate deception. According to a large volume of work by Ekman dating back to 1974 (Ekman, 2001; 2003), as well as collaborative work with O'Sullivan and Frank (1999; 1991), human facial expressions are reliable indicators of deliberate deceptive behavior. The potential value of practical security applications of Ekman's principles and techniques in the contemporary climate of global terrorism and counterterrorism is difficult to overestimate, particularly in light of evidence by Ekman, O'Sullivan, and Frank (1991), DePaulo, Lindsay, and Malone et al. (2003), and numerous others reported in scientific literature (Stanovich, 2007) conclusively establishing the universality of human facial expressions and cues to deliberate deception and concealment of emotions and intent across all human cultures.

Within the law enforcement community, behavioral and verbal cues have already provided tremendous usefulness in the area of the dynamic investigatory interview (Sandoval, 2008), written statements (Adams, 2002), and the comprehensive forensic analysis of both written and recorded statements (Adams, 2002; Granhag & Stromwoll, 2005; Sandoval, 2008). Since the inception of the Global War on Terror, initiated by U.S. and international counterterrorism authorities in the wake of the September 11, 2001 terrorist attacks on the United States, both domestic and international law enforcement and counterterrorism agencies have incorporated the techniques developed by Ekman and others to increase the efficiency and probability of identifying unintentional and subconscious human behaviors consistent with the deliberate concealment of intentions and deception in furtherance of terrorist acts.

To date, the Federal Bureau of Investigation (FBI), Central Intelligence Agency (CIA), various components of the Department of Homeland Security (DHS), and state and local law enforcement authorities have included specific training in the deception detection techniques developed by Ekman since 1974 (Ekman, 2003). In the future, it is likely that the same techniques will be further developed through their incorporation into sophisticated video surveillance technologies to enable faster, more efficient, and automatic implementation — particularly in vulnerable venues associated with large volumes of public traffic, such as airports, and at high-value targets of both domestic and international terrorism.

Fundamental Human Emotions and Facial Expression

The pioneering work of Ekman since 1974 demonstrated that seven specific human emotions are universally associated with clearly recognizable facial signals: anger, sadness, fear, surprise, disgust, contempt, and happiness (Ekman, 2003; Ekman & O'Sullivan, 1999; Ekman & Frank, 1991). Numerous contemporaneous and subsequent studies have confirmed the specific mechanism responsible for this phenomenon in the involuntary patterns of movement of 43 different human facial muscles corresponding to the emotional state of the individual (Stanovich, 2007).

According to psychologists and anthropologists, human beings naturally evolved both universal facial expressions and the ability to deliberately conceal their emotions — especially fear (Ekman, 2003; Stanovich, 2007) — through natural selection. Furthermore, a minority of individuals are naturally much better than others at concealing their true emotions and reactions to external circumstances (Mann, Vrij, & Bull, 2002). Likewise, a minority of individuals are much better at recognizing deception through the observation of facial features, although in most cases they are not consciously aware of how they do so (Park, Levine, & McCornack et al., 2002).

Detection of Deliberate Deception Through Observation

In that regard, Ekman introduced the fundamental concept of practical training of law enforcement and security professionals in distinguishing genuine facial expressions — consistent with the true expression of inner emotional state and the absence of any deliberate attempt to conceal or misrepresent emotions or intentions — from manipulated or falsified expressions of outward facial cues (Ekman, 2003; Ekman & O'Sullivan, 1999; Ekman & Frank, 1991). According to Ekman and others (DePaulo, Lindsay, & Malone et al., 2003; Mann, Vrij, & Bull, 2002; Park, Levine, & McCornack et al., 2002; Vrij, Edward, & Bull, 2001), facial expressions deliberately designed merely to mimic the expressions commonly associated with emotions — most typically happiness — are clearly differentiable from genuine expressions corresponding to inner emotional states by virtue of characteristic differences in muscular contractions and in the different patterns of muscular invocation.

In principle, the facial mannerisms consistent with deliberate concealment of emotional state and intention are merely one component of the full spectrum of evolutionary adaptations in the realm of deceptive behavior. This spectrum also includes elements of body language and vocal intonation designed to achieve the same purpose (Park, Levine, & McCornack et al., 2002; Stanovich, 2007). Observations of both body language and numerous elements of speech patterns betray true sentiments and intentions among humans as well as among myriad nonhuman animal species. The range of deceptive displays includes feigned expressions of boredom — such as yawning to conceal fear in primates and many other mammalian species — and artificial displays of maximum physical size, such as exaggeratedly erect posture and expansion of the chest to communicate imposing physical stature and conceal intimidation (Stanovich, 2007).

The primary difference between facial expressions and other physical and behavioral manifestations of concealed emotions and deceptive intent in humans is that facial expressions are uniquely susceptible to involuntary indications of their duplicitous nature. These manifest as specific, objectively observable characteristic differences between genuine facial expressions and those deliberately contrived for the purpose of deception (Ekman, 1991; 2003).

Transmission of Subconscious Intent Through Involuntary Micro-Expressions

Ekman's studies disclosed that fake human smiles typically use fewer facial muscles and rely primarily on the zygomatic major muscle, whereas genuine human smiles invoke the zygomatic major muscle in conjunction with the orbicularis oculi and the pars lateralis. The practical significance of these distinctions arises from three combined observations: (1) very few individuals are capable of deliberately manipulating the latter muscle groups; (2) the differences in muscular contractions attributable to those distinctions are readily observable in human expressions; and (3) specific training in the recognition of such characteristic patterns enables trained individuals — such as law enforcement officers and security personnel — to dramatically increase their rate of recognition and ability to distinguish genuine facial expressions from deliberately deceptive ones.

While it is possible for most individuals to deliberately conceal their true emotions and intentions to some degree, careful analysis of facial expressions reveals that even relatively accomplished liars exhibit characteristic clues to their true thoughts in very subtle muscular contractions that betray their efforts at concealment. Ekman (1991) coined the term micro-expressions to describe these minute involuntary muscular contractions that typically occur in less than one-quarter of a second and are therefore substantially imperceptible to most observers (Ekman, 1991; 2003; 2006).