The theory behind micro‐expressions posits that when people attempt to mask their true emotional state, expressions consistent with their actual state will appear briefly on their face. Thus, while people are generally good at hiding their emotions, some facial muscles are more difficult to control than others and automatic displays of emotion will produce briefly detectable emotional “leakage” or micro‐expressions (Ekman, 1985). When a person does not wish to display his or her true feelings s/he will quickly suppress these expressions. Yet, there will be an extremely short time between the automatic display of the emotion and the conscious attempt to conceal it, resulting in the micro‐expression(s) that can betray a true feeling and according to theory, aid in detecting deception.
…The METT Advanced programme, marketed by the Paul Ekman Group (2011), coined an “online training to increase emotional awareness and detect deception” and promoted with claims that it “… enables you to better spot lies” and “is meant for those whose work requires them to evaluate truthfulness and detect deception—such as police and security personnel” (Paul Ekman Group, METT Advanced‐Online only, para. 2). The idea that micro‐expression recognition improves lie detection has also been put forth in the scientific literature (Ekman, 2009; Ekman & Matsumoto, 2011; Kassin, Redlich, Alceste, & Luke, 2018) and promoted in the wider culture. One example of this is its use as a focal plot device in the crime drama television series Lie to Me, which ran for three seasons (Baum, 2009). Though a fictional show, Lie to Me was promoted as being based on the research of Ekman. Ekman himself had a blog for the show in which he discussed the science of each episode (Ekman, 2010). Micro‐expression recognition training is not only marketed for deception detection but, more problematically, is actually used for this purpose by the United States government. Training in recognising micro‐expressions is part of the behavioural screening programme, known as Screening Passengers by Observation Technique (SPOT) used in airport security (Higginbotham, 2013; Smith, 2011; Weinberger, 2010). The SPOT programme deploys so‐called behaviour detection officers who receive various training in detecting deception from nonverbal behaviour, including training using the METT (the specific content of this programme is classified, Higginbotham, 2013). Evidently, preventing terrorists from entering the country’s borders and airports is an important mission. However, to our knowledge, there is no research on the effectiveness of METT in improving lie detection accuracy or security screening efficacy.
…Our findings do not support the use of METT as a lie detection tool. The METT did not improve accuracy any more than a bogus training protocol or even no training at all. The METT also did not improve accuracy beyond the level associated with guessing. This is problematic to say the least given that training in the recognition of micro‐expressions comprises a large part of a screening system that has become ever more pervasive in our aviation security (Higginbotham, 2013; Weinberger, 2010).
Hat tip the excellent Rolf Degen on twitter.