"Mental mediumship" is communication of spirits with a medium by telepathy. The medium mentally "hears" (clairaudience), "sees" (clairvoyance), and/or feels (clairsentience) messages from spirits. Directly or with the help of a spirit guide, the medium passes the information on to the message's recipient(s). When a medium is doing a "reading" for a particular person, that person is known as the "sitter".
Magicians have a long history of exposing the fraudulent methods of mediumship. Early debunkers included Chung Ling Soo, Henry Evans and Julien Proskauer. Later magicians to reveal fraud were Joseph Dunninger, Harry Houdini and Joseph Rinn. Rose Mackenberg, a private investigator who worked with Houdini during the 1920s, was among the most prominent debunkers of psychic fraud during the mid-20th century.
^ Joseph McCabe. (1920). Spiritualism: A Popular History from 1847. Dodd, Mead and Company. pp. 110–12. A Mr. Merrifield was present at one of the sittings. Home's usual phenomena were messages, the moving of objects (presumably at a distance), and the playing of an accordion which he held with one hand under the shadow of the table. But from an early date in America he had been accustomed occasionally to "materialise" hands (as it was afterwards called). The sitters would, in the darkness, faintly see a ghostly hand and arm, or they might feel the touch of an icy limb. Mr. Merrifield and the other sitters saw a "spirit-hand" stretch across the faintly lit space of the window. But Mr. Merrifield says that Home sat, or crouched, low in a low chair, and that the "spirit-hand" was a false limb on the end of Home's arm. At other times, he says, he saw that Home was using his foot."
In 2013 Rose Marks and members of her family were convicted of fraud for a series of crimes spanning 20 years entailing between $20 and $45 million. They told vulnerable clients that to solve their problems they had to give the purported psychics money and valuables. Marks and family promised to return the cash and goods after "cleansing" them. Prosecutors established they had no intent to return the property. https://drive.google.com/file/d/1ZxhJSNFx0QgywAEljeOS_TUw5e9jgeq8/view?usp=sharing
In the late 19th century, the fraudulent methods of spirit photographers such as David Duguid and Edward Wyllie were revealed by psychical researchers. Hereward Carrington documented various methods (with diagrams) how the medium would manipulate the plates before, during, and after the séance to produce spirit forms. The ectoplasm materializations of the French medium Eva Carrière were exposed as fraudulent. The fake ectoplasm of Carrière was made of cut-out paper faces from newspapers and magazines on which fold marks could sometimes be seen from the photographs. Cut out faces that she used included Woodrow Wilson, King Ferdinand of Bulgaria, French president Raymond Poincaré and the actress Mona Delza.
Senses used by mental mediums are sometimes defined differently from in other paranormal fields. A medium is said to have psychic abilities but not all psychics function as mediums. The term clairvoyance, for instance, may include seeing spirit and visions instilled by the spirit world. The Parapsychological Association defines "clairvoyance" as information derived directly from an external physical source.