Plate from Mechanisme de la Physionomie Humaine,

1862

The French neurologist Guillaume Duchenne de Boulogne was the first person to empirically test the idea that emotional expressions can be understood as movements of facial muscles, an idea now taken for granted. Duchenne applied electrical currents to facial muscles and with newly invented photographic techniques recorded the movements of the face. His research influenced Charles Darwin and generations of modern psychologists. The most popular coding system at present, the Facial Action Coding System, used for classifying emotions in psychology and computer science, is partly based on Duchenne’s research. This plate shows photographs of expressions after stimulation of the corrugator supercilii, one of the muscles controlling the eyebrows. Duchenne believed this muscle completely controlled expressions of pain. By covering half the face, he could demonstrate that the expression was due to local movements of the eyebrow rather than movements across the whole face.