One of Darwin's less famous books, The Expression of the Emotions in Man and Animal, mentions an experiment conducted by Darwin himself, in which he asked subjects to describe the emotions found on unlabeled pictures of human faces. A new historical study recently published in the Journal of the History of the Neurosciences revisits this experiment, determined to be the first ever single-blind study of human perception of emotional expression. Darwin selected 11 pictures out of the 65 available from French neurologist G.B.A. Duchenne's own studies on facial muscles and emotions. He then randomly showed these images to 24 subjects, without title or label, and asked them to describe the emotion. He recorded the results in three data tables and used them to determine which of the images associated the most agreement most with the emotion displayed. The images that made the cut were later published in Darwin's book. Since the experiment was hardly mentioned in the book, little was known about Darwin's methods before this historival study was conducted by Peter J. Snyder. The study also draws parallels between Darwin's experiment and contemporary methods used to test for autism and schizophrenia.