People with electrodes applied to their face to stimulate expressions (1860s).

The French neurologist Guillaume-Benjamin Duchenne who revived the bioelectrical studies of Luigi Galvani (the namesake of Galvanism and a probable inspiration for Frankenstein) published these pics in the book Mécanisme de la physionomie humaine in 1862. Duchenne thought facial expressions were the ‘movement of the soul’ and codified 53 ‘inner states’ that could be classified in terms of muscular action.