Joseph Gaither Pratt (August 31, 1910 – November 3, 1979) was an American psychologist who specialized in the field of parapsychology.

Pratt was co-experimenter in the Pearce–Pratt and Pratt–Woodruff tests that are considered by some parapsychologists to have provided evidence for psi, though critics discovered flaws in the experiments.

[3] He was the principal author of an article in the journal Nature that offered a statistical summary of almost a decade of experiments with the selected participant, Pavel Štěpánek.

J. G. Pratt was born on August 31, 1910,[4] at Winston-Salem in the Piedmont section of North Carolina, the fourth among 10 children of a large farming family.

Pratt came to realize that "my mind was not suited to a profession in which the answers to the great questions regarding man and his relation to the universe are largely taken on faith".

[5] Pratt spent two of his early academic years (1935–1937) at Columbia University, upon the invitation of Gardner Murphy to there seek to replicate the results of forced-choice ESP experiments, as offered by J.

From 1937, Pratt worked as Research Associate, and then as Assistant Director, of the Parapsychology Laboratory at Duke University, under Rhine.

Pratt and the divinity student Hubert Pearce performed a long distance ESP experiment at the Duke University in 37 sittings between August 1933 and March 1934.

[8] In 1960, C. E. M. Hansel investigated the Duke Campus and found that it would have been easy for Pearce to have left the library during the experiment to approach Pratt's room and watch him turn over the cards.

According to John Sladek "The room had a clear window giving on to the corridor, a trap door with a hole in it situated right above Pratt's table and Hansel found that he could stand up on the chair in the corridor and peer through a crack at the top of the door to see the cards.

[8] Paul Kurtz wrote that "Pratt could easily have peeked at the Zener cards by sneaking out of the library to the sender's office, or by using an accomplice.

"[9] Hansel came to the conclusion that the possibility of trickery had not been ruled out in the experiment, the subject was left unobserved in the library, the room used by Pratt was not screened to make it impossible for outsiders to see inside and the reports themselves contained conflicting statements so because of these factors the experiment could not be regarded as supplying evidence of ESP.

Hansel responded to this by claiming the building plan was not to scale and would not alter his argument, as the simplest way for Pearce to have cheated on the experiment would have been to observe the cards from the corridor, and this possibility was not ruled out.

Many other precautions with the handling of the data were not taken, giving Pearce or Pratt a number of opportunities to change the figures.

[2]Martin Gardner claimed to have inside information that files in Rhine's laboratory contain material suggesting fraud on the part of Pearce.

[1] Critics pointed out that there were serious weaknesses in the experiment so that if the experimenter could learn the position of even one of the key cards he could increase the number of hits.

In 1960, C. E. M. Hansel visited the Parapsychology Laboratory and investigated the apparatus and discovered the experiment did not rule out the possibility of trickery.

John Sladek wrote regarding Hansel's discovery: He found that, though the key cards are hung on their pegs in a different order for each run (each twenty-five trials), it is certainly possible for E to guess the new positions of one or two of them.

When the screen is laid on its side after a run, E notes that the key card in Position 1 (the right- or left-hand end) is, say, a cross.

Hansel wrote the counter-criticisms from Pratt and Woodruff did not hold up to scrutiny as the results from the experiment could have originated through the use of a trick then it cannot be claimed to provide evidence for ESP.