Extra-sensory perception (ESP), often referred to as "sixth sense," is defined in parapsychology as the ability to acquire information by paranormal means. ESP is not dependent on the known physical senses, nor on deduction from previous experience. Information can be about present, future, or past events, objects, or people.
As with all paranormal or "psi" phenomena, the existence of ESP continues to be the subject of debate between skeptics, critics, and believers. Yet the conviction that there is more to our world and our existence in it than can be experienced through the five physical senses drives researchers to continue to report and study this phenomenon.
The term Extra-sensory perception (ESP) was used by researcher and parapsychologist J. B. Rhine to denote "paranormal" abilities such as telepathy and clairvoyance. Some of the more prominent types of extra-sensory perception or ESP include:
Several of these types of ESP are often present in mediumship, as well as others like aura reading and channeling. People adept at using their paranormal abilities are often known as psychics. ESP and other forms of paranormal phenomena are often referred to by the blanket term "psi." Parapsychologists differentiate between paranormal phenomena of a cognitive nature like ESP (psi-gamma) and paranormal action like psychokinesis (psi-kappa).
The concept of extra-sensory perception has been a part of many cultures throughout history. Precognition and prophesy have been an important part of many cultures, including the Celts of the Scottish Highlands, the Sami in Scandinavia, the Native Americans, the Zulus of Africa, and the Maori of New Zealand. ESP abilities have also been a part of spiritual development, such as in Hinduism, which lists clairvoyance as part of one of the siddhis, or skills that can be acquired through meditation and discipline.
ESP was reportedly observed in the early days of hypnosis among the followers of Franz Anton Mesmer. Patients put into a trance state were observed to demonstrate telepathic abilities, vision with the fingertips, and clairvoyance. Unlike the parapsychologists to come, the followers of Mesmer believed such abilities to have a physiological cause, not a paranormal one.
As Spiritualism gained popularity in the mid-nineteenth century, more scientists and researchers became interested in psi phenomena. In 1882, the British Society for Psychical Research was founded to study paranormal phenomena like ESP. A few years later, in 1885, the American Society for Psychical Research was founded.
One of the most well known researchers of ESP was J. B. Rhine. Beginning in the 1930s, Rhine worked on a number of experiments designed to test for ESP at Duke University in North Carolina. Using sets of Zener cards (often referred to as "ESP cards"), Rhine tested for ESP; results above the chance statistics were attributed to psi phenomena. Rhine carefully defined terms like "ESP" and "psi," and continued to research psi phenomena at Duke until his retirement in 1965, when he transferred his research to the Foundation for Research on the Nature of Man. Due at least in part to the work Rhine and his associates performed, parapsychology has become established in other universities.
Some of the first studies in what would be later termed ESP were conducted by William Barrett in 1881, shortly before he assisted in the founding of the Society for Psychical Research. Barrett investigated the case of the five Creery sisters, who were between the ages of ten and seventeen and could apparently use telepathy to psychically identify an object that had been selected in their absence. After sending one sister out of the room, Barrett would write the name of an object on a piece of paper, which he would then show to the remaining sisters. The first girl was then called back in, and usually guessed the name of the object correctly. Later, a second set of experiments was done involving playing cards. It was not until after the investigators had published their results that it was discovered that the girls had used a number of signals, including slight head movements and coughing, to tell their sister what to guess, thereby nullifying the results of the experiments.
In the 1920s, investigator G. N. M. Tyrrell created automated devices to randomize target selection, and others experimented with drawings or token objects. The most well-known results, however, were not until the 1930s, when J. B. Rhine began his series of experiments. To test ESP, Rhine would use decks of Zener cards, consisting of five different designs. In some experiments, cards were laid face down for the subject to guess, to test clairvoyance; in others, the researcher would hold the card so that the subject could not see it, to test telepathy. Based on the laws of chance, it would be expected that participants would be able to guess one out of five symbols correctly, but Rhine found that subjects often exceeded these expectations, even if it was only by a small percentage.
In the 1970s, parapsychologists began using ganzfeld experiments to test for ESP ability. Ganzfeld tests attempt to discern telepathy by separating two individuals into isolated rooms, where one attempts to send a telepathic image to the other. The sender of the message is generally shown either a still image or a short video clip, which he or she then attempts to send to the receiver. The receiver sits in a comfortable reclining chair under a red light, wearing headphones that play white noise or pink noise, and has his or her eyes covered with halves of ping pong balls. These conditions help the receiver enter what is termed the "ganzfeld state," a trance-like state similar to being in a sensory deprivation chamber. After the sender has attempted to send the image for a set number of time (generally 20 to 40 minutes), the receiver is asked to choose the correct image out of a group of four images. Parapsychologists have collected the results of approximately 700 individual ganzfeld sessions performed by about two dozen investigators, and claim the correct image is selected 34 percent of the time. This increase above the 25 percent that would be expected from chance alone has been cited as proof of the existence of telepathy, although critics point out numerous ways in which ganzfeld experiments may be flawed.
Researchers have found that ESP abilities are apparently heightened under hypnosis. The results of experiments have been found to be consistently higher when subjects are put into a trance state than when they retain normal consciousness. Since hypnosis typically involves relaxation and suggestion in an atmosphere of friendliness and trust, it is thought that perhaps one of these factors, or a combination thereof, may be responsible for heightened psi scores.
The absence of psi ability is also sometimes considered significant. Researchers employ the term "psi-missing" to denote situations where the subject consistently scores below what would be expected by chance. According to experimental results, believers in psi tend to score higher, whereas skeptics often score significantly below chance. This phenomenon, referred to as the "Sheep-goat effect" (where believers are "sheep" and non-believers are "goats"), has been observed by many researchers. Explanations involve the idea that one's attitudes may affect one's reality; disbelievers may create a void of psi experiences, while believers experience the opposite.
A great deal of reported ESP is said to occur spontaneously under conditions which are not scientifically controlled. Such experiences have often been reported to be much stronger and more obvious than those observed in laboratory experiments. These anecdotal incidents, rather than laboratory evidence, have served as the basis for the extremely widespread belief in the authenticity of psi phenomena. However, because it has proven extremely difficult (perhaps impossible) to replicate such extraordinary experiences under controlled scientific conditions, skeptics regard them as unproven hearsay. Eyewitness accounts can be flawed; memories tend to be become modified when the experience is spoken about often or when there is emotional involvement in the subject matter; and people may misinterpret anomalous occurrences which, while unusual, may have perfectly normal explanations. While situations with more emotional attachment may have stronger ESP effects (sensing that a loved one has been in a car crash, for example), such situations would be difficult and morally reprehensible to replicate for testing purposes. Strong ESP effects remain anecdotal, and skeptics remain unconvinced of their veracity. Supporters of ESP maintain that the more subtle effects proven in the laboratory support the existence of larger effects.
Proponents of the existence of ESP point to numerous scientific studies that appear to offer evidence of the phenomenon's existence: the work of parapsychologist J. B. Rhine, and physicists Russell Targ and Harold E. Puthoff in the 1970s are often cited in arguments that ESP exists. Skeptics like James Randi, however, have argued that most of these studies were not conducted with proper scientific controls, and that many studies did not adequately protect against fraud or manipulation. Due to the nature of ESP, results are also often difficult to replicate, even within the same experiment using the same subject and researcher. Parapsychologists call one such effect the "decline effect," which describes how a subject's initial performance often slowly declines as testing continues.
While there have been numerous proven examples of willful fraud, such as the case of the Creery sisters, skeptics often discuss the possibility of unconscious fraud (as well as the fact that prominent researchers have been historically duped by simple mentalist techniques). For example, during ganzfeld testing, the handling of a printed target image by the sender may create subtle differences, such as creases or textural changes, that may cause the receiver to choose the target image out of a group, even though he/she may not have consciously noticed such handling marks. Researchers have, over time, responded to critiques of their experimental protocol to combat such criticism; the ganzfeld tests are one such test that has gone through a number of revisions, as well as critiques by well-known mentalists in order to make it a more reliable gauge of ESP phenomena. But the simple fact that fraud has, in many instances, been a part of alleged ESP phenomena has made it hard for the concept to gain legitimacy in scientific circles. Only 10 percent of polled members of the National Academy of Sciences felt that parapsychological research should be encouraged; 25 percent felt it should actively be discouraged.
While some ESP studies have been published that fail to find any evidence indicating the existence of ESP, it can be argued that the vast majority of such studies suffer from what is called the "file drawer effect;" in essence, studies that fail to support the existence of ESP are never put out for public examination. This may be because parapsychologists have historically had to fight to be recognized as a legitimate science, and do not wish to provide any further evidence that can be cited by critics, as well as potentially having an effect on the funding of future studies. If such studies had been published, however, they could have certainly influenced meta-analyses.
Fraud and methodological flaws aside, parapsychologists continue to produce what they consider statistically significant results. Dean Radin has argued that the positive results from reputable studies, when analyzed using meta-analysis, provide strong evidence for ESP that is almost impossible to account for using any other means except broad-based charges of fraud. Critics have argued that such statistics are not as significant as claimed, and do not deviate from chance enough to constitute proof of any external effect. Skeptics such as Raymond Hymen, who evaluated the CIA's clairvoyance experiments in the Star Gate program, have said that such phenomena may not have been proven to exist, but that findings were promising enough to merit continued research.
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