Magicians have a long history of exposing the fraudulent methods of mediumship. Early debunkers included Chung Ling Soo, Henry Evans and Julien Proskauer.[62] 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.[63]
Physical mediumship is defined as manipulation of energies and energy systems by spirits. This type of mediumship is claimed to involve perceptible manifestations, such as loud raps and noises, voices, materialized objects, apports, materialized spirit bodies, or body parts such as hands, legs and feet. The medium is used as a source of power for such spirit manifestations. By some accounts, this was achieved by using the energy or ectoplasm released by a medium, see spirit photography.[26][27] The last physical medium to be tested by a committee from Scientific American was Mina Crandon in 1924.

In 1970 two psychical researchers investigated the direct-voice medium Leslie Flint and found that all the "spirit" voices in his séance sounded exactly like himself and attributed his mediumship to "second-rate ventriloquism".[173] The medium Arthur Ford died leaving specific instructions that all of his files should be burned. In 1971 after his death, psychical researchers discovered his files but instead of burning them they were examined and discovered to be filled with obituaries, newspaper articles and other information, which enabled Ford to research his séance sitters backgrounds.[174]

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.[37]