In 1862 Dr. Duchenne has published a treatise, Méchanisme de la Physionomie Humaine, full of photographs in which he analyzes the movements of the facial muscles, caused by using electrical stimuli.
Charles Darwin published in 1872 “The expression of emotions in man and animals” documentation to show that the main expressions of humans and animals are innate and product evolution.
Paul Ekman and Wallace V. Friesen, University of California, published Unmasking the Face and repeated studies of the musculature in the facial expression, the expression of emotions in cross-cultural context, the universality of core emotions independent of culture.
The Facial Action Coding System (FACS) measure and classify the muscular movements of the face, and proposes a systematic treatment of the expression of emotions developed in 1969 by Carl-Herman Hjortsjo, Swedish professor of anatomy at the University of Lund, subsequently picked up by Paul Ekman and Wallace V. Friesen.
In 2013 and 2014 the University of Glasgow has published studies of the facial muscles that have allowed to identify basic facial expressions that would be four and not six: joy and sadness, surprise-fear and anger-disgust that have been grouped together because they are expressed and made recognizable by the activation of the same facial muscles. Through this research are also highlighted “cultural” differences in the expression of emotions between the type Caucasian and East Asian.
In the era of the advanced studies for the automated face recognition and microexpressions detection it is still possible to imagine a totally new facial expression. What emotion is it?