Cold reading also explains why psychics have consistently failed scientific tests of their powers. By isolating them from their clients, psychics are unable to pick up information from the way those clients dress or behave. By presenting all of the volunteers involved in the test with all of the readings, they are prevented from attributing meaning to their own reading, and therefore can't identify it from readings made for others. As a result, the type of highly successful hit rate that psychics enjoy on a daily basis comes crashing down and the truth emerges – their success depends on a fascinating application of psychology and not the existence of paranormal abilities.
In 1880 the American stage mentalist Washington Irving Bishop published a book revealing how mediums would use secret codes as the trick for their clairvoyant readings. The Seybert Commission was a group of faculty at the University of Pennsylvania who in 1884–1887 exposed fraudulent mediums such as Pierre L. O. A. Keeler and Henry Slade. The Fox sisters confessed to fraud in 1888. Margaret Fox revealed that she and her sister had produced the "spirit" rappings by cracking their toe joints.