In a series of experiments in London at the house of William Crookes in February 1875, the medium Anna Eva Fay managed to fool Crookes into believing she had genuine psychic powers. Fay later confessed to her fraud and revealed the tricks she had used. Frank Herne a British medium who formed a partnership with the medium Charles Williams was repeatedly exposed in fraudulent materialization séances. In 1875, he was caught pretending to be a spirit during a séance in Liverpool and was found "clothed in about two yards of stiffened muslin, wound round his head and hanging down as far as his thigh." Florence Cook had been "trained in the arts of the séance" by Herne and was repeatedly exposed as a fraudulent medium.
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.