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Extrasensory perception, usually abbreviated to ESP, describes a way of communicating or of being aware of something without using the known senses. An awareness of another person's thoughts without the use of sight, hearing, taste, touch, or smell would be an example of ESP. The study of extrasensory perception is part of the field of psychology called parapsychology. The evidence for the existence of ESP is highly debatable. Most scientists believe ESP is something whose existence is yet to be proved.
What parapsychologists study. Extrasensory perception is commonly divided into three kinds of phenomena--(1) telepathy, (2) clairvoyance, and (3) precognition. Telepathy is the sensing of the thoughts or feelings of one person by another in some unknown way. Clairvoyance is an awareness of objects, events, or people without the use of the known senses. Precognition is knowledge of a future event by means of telepathy or clairvoyance. Some parapsychologists also study phenomena related to ESP, such as psychokinesis. Psychokinesis is the mental control of physical objects and includes effects such as influencing the fall of dice by concentration.
ESP research. Many classic ESP experiments, developed and used mainly between 1930 and 1960, involved card guessing. A pack of 25 special ESP cards (also called Zener cards, after the American psychologist Karl E. Zener) was often used. Each ESP card has one of five different symbols on it, such as a circle or cross. In a simple test of telepathy, a person called the sender would look at or think of a given card and concentrate on its symbol. A second person, called the receiver, was usually in another room and would attempt to name the symbol that the sender was thinking of. In an experiment on clairvoyance, cards would be taken from the pack one at a time, and the receiver would try to name the symbols on the cards. In this case, the person taking the cards would not look at the symbol.
In these experiments, one would expect 5 correct answers out of 25 calls just by chance if the receiver were only guessing at what was on the cards. Most parapsychologists would consider a person who consistently averaged 7, 8, or more correct calls after many tests to have some ESP ability.
The use of computers and electronic random-number devices has almost entirely replaced the use of cards in ESP experiments. Some such research has produced controversial claims that subjects are able to influence or predict the decay of radioactive substances. This kind of influence or prediction is impossible in terms of modern scientific understanding.
Possible misunderstandings. In spite of the lack of widely accepted evidence about ESP, many people believe that it is valid because of personal experiences that seem to be unexplainable otherwise. But most of these experiences can be explained by psychological processes that most people are not aware of. People often do not know how events around them set off their thoughts. Two people who know each other well may both experience a similar chain of thoughts when exposed to a common stimulus. For example, a husband and wife may be reading together and not paying much attention to music on a radio. Then certain music triggers in each of them the memory of a person they met several years ago but have not encountered since. Just as one of them is about to bring up the person's name, the other one mentions it. These similar thoughts may seem to be an instance of extrasensory perception. But neither person is likely to realize that both of their thoughts were actually set off by the music in the background.
Debate about ESP. One of the most noted ESP researchers was J. B. Rhine, an American who headed the Parapsychology Laboratory at Duke University in the United States for many years. Rhine conducted a number of card-guessing experiments to test clairvoyance, precognition, and telepathy. Some researchers claim that evidence based on the work of Rhine and other investigators, most of them in England, has established beyond question the existence of ESP.
But other researchers believe that the evidence is questionable. In the early days of ESP research, when fairly crude experiments were used, some people put on rather remarkable telepathic or clairvoyant performances. Today, however, when experiments are more carefully controlled, similar performances are rare. In science, the trend should generally be in the opposite direction. That is, if the phenomena under investigation are real, improved experiments should produce more significant and well-defined results.
Another reason for scepticism is that after more than a hundred years of research, no scientist has been able to produce a repeatable demonstration of ESP that can be performed before a group of neutral scientists. Some parapsychologists have responded to this criticism by arguing that the fault may lie with the experimenter. These parapsychologists suggest that sceptical researchers may have attitudes that prevent them from producing or witnessing ESP.
Continued belief in ESP is likely to endure regardless of the weakness of the evidence. Many people strongly believe that some elements of human existence are not subject to physical laws or methods. ESP, if it could be proved to exist, would help to explain these elements.
ESP might also give insights into the possibility of life after death. Rhine, for example, investigated the potential link of ESP to life after death. The Society for Psychical Research, founded in England in the late 1800's, made similar investigations. Interest in ESP and other parapsychological phenomena will probably continue as long as people hope to survive after death or to bypass limits imposed by science.
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