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. https://drive.google.com/file/d/1j9OXTL0I-NYzWv7GGPZjWvnWCNACHJFh/view?usp=sharing
The trance medium Leonora Piper was investigated by psychical researchers and psychologists in the late 19th and early 20th century. In an experiment to test if Piper's "spirit" controls were purely fictitious the psychologist G. Stanley Hall invented a niece called Bessie Beals and asked Piper's 'control' to get in touch with it. Bessie appeared, answered questions and accepted Hall as her uncle. The psychologist Joseph Jastrow wrote that Piper pretended to be controlled by spirits and fell into simple and logical traps from her comments. Science writer Martin Gardner concluded Piper was a cold reader that would "fish" for information from her séance sitters. The physiologist Ivor Lloyd Tuckett who examined Piper's mediumship in detail wrote it could be explained by "muscle-reading, fishing, guessing, hints obtained in the sitting, knowledge surreptitiously obtained, knowledge acquired in the interval between sittings and lastly, facts already within Mrs. Piper's knowledge."
Ray Hyman discovered many methodological errors with Schwartz's research including; "Inappropriate control comparisons", "Failure to use double-blind procedures", "Creating non-falsifiable outcomes by reinterpreting failures as successes" and "Failure to independently check on facts the sitters endorsed as true". Hyman wrote "Even if the research program were not compromised by these defects, the claims being made would require replication by independent investigators." Hyman criticizes Schwartz's decision to publish his results without gathering "evidence for their hypothesis that would meet generally accepted scientific criteria... they have lost credibility."
^ "Glossary of Key Words Frequently Used in Parapsychology" Archived 2010-12-24 at the Wayback Machine, Parapsychological Association website. "Materialization: A phenomenon of physical mediumship in which living entities or inanimate objects are caused to take form, sometimes from ectoplasm." Retrieved January 24, 2006 "Medium – Definition". Dictionary.com. Retrieved 23 March 2007.