C ould a program detect potential terrorists by reading their facial expressions and behavior? This was the hypothesis put to the test by the US Transportation Security Administration TSA in , as it began testing a new surveillance program called the Screening of Passengers by Observation Techniques program, or Spot for short. While developing the program, they consulted Paul Ekman, emeritus professor of psychology at the University of California, San Francisco. Decades earlier, Ekman had developed a method to identify minute facial expressions and map them on to corresponding emotions. But when the program was rolled out in , it was beset with problems. Officers were referring passengers for interrogation more or less at random, and the small number of arrests that came about were on charges unrelated to terrorism. Even more concerning was the fact that the program was allegedly used to justify racial profiling.
Seeing Emotion in Facial Expressions
How Do You Know Which Emotion a Facial Expression Represents? - Scientific American Blog Network
Leading scientific thinkers of their time, such as Aristotle, Rene Descartes, Guillaume Duchenne, and Charles Darwin, have long promoted the idea that there are a handful of basic emotions that people express. In recent decades, that group has crystalized into six core emotions: happiness, surprise, sadness, anger, fear, and disgust. But there are clearly many shades of gray between those emotions. Martinez wanted to know whether compound emotions, such as happy surprise, were expressed using the same muscle movements of both happiness and surprise, or whether the expression involved a unique set of muscles that represented some amalgam of the two. What he and his colleagues found was that the human face makes 21 different emotional expressions — and each is different from the other. While some represented combinations of emotions, each differed in terms of which muscles were involved. And surprisingly, these facial expression patterns were remarkably consistent across all volunteers.
Don’t look now: why you should be worried about machines reading your emotions
A facial expression  is one or more motions or positions of the muscles beneath the skin of the face. According to one set of controversial theories, these movements convey the emotional state of an individual to observers. Facial expressions are a form of nonverbal communication. They are a primary means of conveying social information between humans , but they also occur in most other mammals and some other animal species.
Facial expression is usually synthesized or predicted on the basis of a given emotion. The prototypical expressions for basic emotions happiness, sadness, surprise, disgust, anger, and fear as postulated by discrete emotion psychologists are rather consistently produced and interpreted among different cultures, and can be used as icons to represent a basic emotion. However, these facial expressions are actually rarely observable in every day affective episodes, because of the complexity and multi-functional nature of facial expression and a high inter-individual variance. This article sketches the different functions of facial expression and presents and alternative way to predict, synthesize, and understand facial behavior.