The psychologists Donovan Rawcliffe (1952), C. E. M. Hansel (1980), Ray Hyman (1989) and Andrew Neher (2011) have studied the history of psi experiments from the late 19th century up until the 1980s. In every experiment investigated, flaws and weaknesses were discovered so the possibility of sensory leakage and trickery were not ruled out. The data from the Creery sister and the Soal-Goldney experiments were proven to be fraudulent, one of the subjects from the Smith-Blackburn experiments confessed to fraud, the Brugmans experiment, the experiments by John Edgar Coover and those conducted by Joseph Gaither Pratt and Helmut Schmidt had flaws in the design of the experiments, did not rule out the possibility of sensory cues or trickery and have not been replicated.