from 1940 to 1950 but refused to give the names of the participants in the studies. Massimo Pigliucci has written: Most damning of all, Rhine admitted publicly that he had uncovered at least twelve instances of dishonesty among his researchers in a single decade, from 1940 to 1950. However, he flaunted standard academic protocol by refusing to divulge the names of the fraudsters, which means that there is unknown number of published papers in the literature that claim paranormal effects while in fact they were the result of conscious deception. Martin Gardner claimed to have inside information that files in Rhine's laboratory contain material suggesting fraud on the part of Hubert Pearce. Pearce was never able to obtain above-chance results when persons other than the experimenter were present during an experiment, making it more likely that he was cheating in some way. Rhine's other subjects were only able to obtain non-chance levels when they were able to shuffle the cards, which has suggested they used tricks to arrange the order of the Zener cards before the experiments started. A researcher from Tarkio College in Missouri, James D. MacFarland, was suspected of falsifying data to achieve positive psi results. Before the fraud was discovered, MacFarland published two articles in the Journal of Parapsychology (1937 & 1938) supporting the existence of ESP. Presumably speaking about MacFarland, Louisa Rhine wrote that in reviewing the data submitted to the lab in 1938, the researchers at the Duke Parapsychology Lab recognized the fraud. "...before long they were all certain that Jim had consistently falsified his records... To produce extra hits, Jim had to resort to erasures and transpositions in the records of his call series." MacFarland never published another article in the Journal of Parapsychology after the fraud was discovered. Some instances of fraud amongst spiritualist mediums were exposed by early psychical researchers such as Richard Hodgson and Harry Price. In the 1920s, magician and escapologist Harry Houdini said that researchers and observers had not created experimental procedures which absolutely preclude fraud. Criticism of experimental results Critical analysts, including some parapsychologists, are not satisfied with experimental parapsychology studies. Some reviewers, such as psychologist Ray Hyman, contend that apparently successful experimental results in psi research are more likely due to sloppy procedures, poorly trained researchers, or methodological flaws rather than to genuine psi effects. Fellow psychologist Stuart Vyse hearkens back to a time of data manipulation,