Extrasensory perception (ESP) (or extra-sensory perception) is the apparent ability to acquire information by paranormal means independent of any known physical senses or deduction from previous experience. The term was coined by Duke University researcher J. B. Rhine to denote psychic abilities such as telepathy, precognition, Retrocognition, Intuition and Psychokinesis. ESP is also sometimes casually referred to as a sixth sense, gut instinct or hunch . The term implies sources of information currently unexplained by science.

Parapsychology is the study of paranormal psychic phenomena, including ESP. Parapsychologists generally regard such tests as the ganzfeld experiment as providing compelling evidence for the existence of ESP. The scientific community does not accept this due to the disputed evidence base, the lack of a theory which would explain ESP, and the lack of experimental techniques which can provide reliably positive results.

History of ESP

The notion of extrasensory perception existed in antiquity. In many ancient cultures, such powers were ascribed to people who purported to use them for second sight or communicate with deities, ancestors, spirits, and the like.

Extrasensory perception and hypnosis

There is a common belief that a hypnotized person would be able to demonstrate ESP. Carl Sargent, a psychology major at the University of Cambridge, heard about the early claims of a hypnosis – ESP link and designed an experiment to test whether they had merit. He recruited 40 fellow college students, none of whom identified themselves as having ESP, and then divided them into a group that would be hypnotized before being tested with a pack of 25 Zener cards, and a control group that would be tested with the same Zener cards. The control subjects averaged a score of 5 out of 25 right, exactly what chance would indicate. The subjects who were hypnotized did more than twice as well, averaging a score of 11.9 out of 25 right. Sargent's own interpretation of the experiment is that ESP is associated with a relaxed state of mind and a freer, more atavistic level of consciousness.[citation needed]

J.B. Rhine

In the 1930s, at Duke University in North Carolina, J. B. Rhine and his wife Louisa tried to develop psychical research into an experimental science. To avoid the connotations of hauntings and the seance room, they renamed it "parapsychology." While Louisa Rhine concentrated on collecting accounts of spontaneous cases, J. B. Rhine worked largely in the laboratory, carefully defining terms such as ESP and psi and designing experiments to test them. A simple set of cards was developed, originally called Zener cards (after their designer)—now called ESP cards. They bear the symbols circle, square, wavy lines, cross, and star; there are five cards of each in a pack of 25.

In a telepathy experiment the "sender" looks at a series of cards while the "receiver" guesses the symbols. To try to observe clairvoyance, the pack of cards is hidden from everyone while the receiver guesses. To try to observe precognition, the order of the cards is determined after the guesses are made.

In all such experiments the order of the cards must be random so that hits are not obtained through systematic biases or prior knowledge. At first the cards were shuffled by hand, then by machine. Later, random number tables were used and, nowadays, computers. An advantage of ESP cards is that statistics can easily be applied to determine whether the number of hits obtained is higher than would be expected by chance. Rhine used ordinary people as subjects and claimed that, on average, they did significantly better than chance expectation. Later he used dice to test for psychokinesis and also claimed results that were better than chance.

In 1940, Rhine, J.G. Pratt, and others at Duke authored a review of all card-guessing experiments conducted internationally since 1882. Titled Extra-Sensory Perception After Sixty Years, it has become recognised as the first meta-analysis in science.[8] It included details of replications of Rhine's studies. Through these years, 50 studies were published, of which 33 were contributed by investigators other than Rhine and the Duke University group; 61% of these independent studies reported significant results suggestive of ESP. Among these were psychologists at Colorado University and Hunter College, New York, who completed the studies with the largest number of trials and the highest levels of significance. Replication failures encouraged Rhine to further research into the conditions necessary to experimentally produce the effect. He maintained, however, that it was not replicability, or even a fundamental theory of ESP that would evolve research, but only a greater interest in unconscious mental processes and a more complete understanding of human personality.