In 1903 and 1904, Stumpf was involved in two public episodes about sensational phenomena. First, an engineer from Prague claimed to have invented a machine that could change photographs of sound waves into sound. Stumpf, after attending a demonstration, wrote an article challenging it, and it was never heard about again. However, the case of Clever Hans, an apparently brilliant horse owned by Herr von Osten, was even more sensational. The research done under his guidance disproved the idea that the animal understood language. It turned out that the horse was following subtle clues given unconsciously by its owner.