During the late 19th century Pierre Janet, a French psychiatrist, treated mental disorders with hypnosis, as did other practitioners of dynamic psychiatry. In particular, he studied the automatic behaviour of mediums to determine the degree to which the subconscious interacts with the conscious during a trance. A medium, while in a self-induced trance, performs spontaneous physical acts with no conscious control. Psychiatry suggests that their apparent messages from a spirit world may actually be subliminal thoughts or feelings, released and given free expression.