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Just the Bat of an Eye

Detecting deception using eye blink rate.

The following post was authored by Kourtney M. Pace. Miss Pace was a student in my Spring 2014, LEJA 300, Police Report Writing class at Western Illinois Universtiy. She submitted the winning entry in the in-class, best-written end-of-semester paper competition.The post was edited for content and to meet formatting requirements.

Using Eye Blink Rate to Detect Deception

Liars tend to blink more because lying is stressful. Under stress, eye blink rate increases (Mann, 2013). People tend to blink more rapidly when they become nervous or when they hear or see something unpleasant (Navarro & Schafer, 2001). Ralph Waldo Emerson once said, "The eyes of men converse as much as their tongues" (Nelson, A., 2010).

Fight/Flight Response

Most liars experience the fight/flight response, which is a physiological reaction to a stressful situation. The fight/flight response is an unconscious, automatic response that provides the body with extra energy to fight off a threat or to flee to fight another day (Schafer, 2012). Most people fear getting caught when they lie. Researchers have found that nervousness causes an increase in eye blink rate (DePaulo et al., 2001; Harrigan & O’Connell, 1996; Tecce, 1992). Additionally, liars are aroused when hiding their true emotions, which in turn increases eye blink rate (Brinke & Porter, 2011). In essence, the fight-or-flight response decreases a liar’s ability to think before he/she acts and consequently an increase in eye blink rate becomes an automatic response in liars and can be a reliable cue to detect deception.

Cognitive Load

Liars are typically under a heavy cognitive load. Under heavy cognitive load, the brain pays more attention to processing critical information than to automatic body functions such as eye blinking. Liars who are under a heavy cognitive load experience an increase in eye blink rate (Navarro, 2009). Cognitive processing is required when people lie. Lying is intentional and deliberate (Gilbert, 1991; Walczyket al., 2003, 2005). Liars must learn how to make themselves believable (Manns, et al., 2012). Consequently, liars must learn what it is their lie target is expecting (Manns, et al., 2012). Liars have to think more about what their response will be (Gilbert 1991; Walczyk et al., 2003, 2005). Liars must not only think about what they have said and will say, but they must also monitor how their target perceives the lie (Vrij et al., 2008). Liars have to maintain the same lie throughout the lying process (Vrij et al., 2008). These tasks can be very challenging, especially under heavy cognitive load causing less conscious attention to eye blink rate.

Less is Not Always More

Lying is very cognitively demanding because they have to put more thought and consideration into their response (Leal & Vrij, 2008). However, researchers argue that cognitive load by itself cannot change eye blink rate during deception (Brinke & Porter, 2011).Some researchers argue that while eye blink rate is an indicator of deception, liars actually tend to blink less (Leal & Vrij, 2008). Others like Leal and Vrij (2008) argue that liars’ eye blink rate actually decreases during the telling of a lie but increases after the lie is told. A majority of the research that is being conducted is done so in a laboratory environment (Navarro, 2012). In an experimental setting, a liar faces no consequences for their actions (Mann, Vrij & Bull, 2002). Therefore, it is a less stimulating (threatening) experience and the results may not reflect the reality of lying. Liars in clinical settings merely act out their roles, decreasing the guilty consciousness of deceiving their lie target (Mann, Vrij & Bull, 2002). Therefore, reality may produce contrary results.

Just a Bat of an Eye Lie

A majority of research supports the hypothesis that increased eye blink rate is a nonverbal cue to deception. Constructing a lie can be very demanding. Liars worry about the possibility of revealing the truth, triggering the fight/flight response. Liars experience a heavy cognitive load, causing less conscious attention to eye blink rate. Research has not identified any one nonverbal or verbal cue to produce a one-hundred percent accuracy rate; however, eye blink rate has been shown to be an effective nonverbal cue to detect deception.


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