You can now help a team at Cambridge University who are studying the images used by Charles Darwin in his book on facial expressions of motion. The Experiment is HERE. The blurb reads;
Between March and November 1868, while Darwin was researching his book The Expression of the Emotions in Man and Animals, he showed a succession of visitors a set of photographs of human faces, some with the muscles artificially contracted by electric probes, and asked them what emotion they thought the photographs conveyed. Darwin’s research has striking parallels with contemporary facial recognition experiments.
There is also a recently published book by Phillip Prodger on how Darwin came to write his book and its impact HERE.