Rivail was in his early 50s when he became interested in séances, which were a popular entertainment at the time. Strange phenomena attributed to the action of spirits were considered a novelty, featuring objects that moved or "tapped", purportedly under the control of 'spirits'. In some cases, this was alleged to be a type of communication: the supposed spirits answered questions by controlling the movements of objects so as to pick out letters to form words, or simply indicate "yes" or "no". At the time, Franz Mesmer's theory of animal magnetism had become popular. When confronted with the phenomena described, some researchers, including Rivail, pointed out that animal magnetism might explain them. Rivail, however, after seeing a demonstration, dismissed animal magnetism as insufficient to explain his observations.