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.
The British medium William Roy earned over £50,000 from his séance sitters. He confessed to fraud in 1958 revealing the microphone and trick-apparatus that he had used. The automatic writings of the Irish medium Geraldine Cummins were analyzed by psychical researchers in the 1960s and they revealed that she worked as a cataloguer at the National Library of Ireland and took information from various books that would appear in her automatic writings about ancient history.