Microexpression

A microexpression is a facial expression with very short duration. It is the innate result of a voluntary and an involuntary emotional response occurring simultaneously and conflicting with one another. It occurs when the amygdala responds appropriately to the stimuli that the individual experiences and wishes to conceal this specific emotion. This results in briefly displaying their true emotions followed by a false emotional reaction.

Human emotions are an unconscious biopsychosocial reaction that derives from the amygdala, and they typically last 0.5–4.0 seconds, although a microexpression will typically last less than 1/2 of a second. It is either very difficult or virtually impossible to hide microexpression reactions. Microexpressions cannot be controlled, but it is possible to capture someone's expressions with a high-speed camera and replay them at much slower speeds. Microexpressions express the seven universal emotions: disgust, anger, fear, sadness, happiness, contempt, and surprise. In the 1990s, Paul Ekman expanded his list of emotions, including a range of positive and negative emotions not all of which are encoded in facial muscles. These emotions are amusement, embarrassment, anxiety, guilt, pride, relief, contentment, pleasure, and shame.