Parapsychology is the study of mental phenomena. Parapsychology currently has two branches.
The first branch deals with circumstances in which a person obtains information, knowledge of another person's thoughts or details of future events without the aid of his ordinary senses, such as sight, hearing or touch; extrasensory perception (ESP) is the term usually applied to such phenomena. The second branch of parapsychology is concerned with the ability of the mind to cause a specific physical occurrence; this is called psychokinesis. 'Psi' is a word that has been used to describe all types of parapsychological phenomena.
Belief in the existence of these phenomena has been widespread since early history; however only during the past 100 years have scientists begun to conduct research into them. Parapsychological beliefs were once considered to be superstitions that could not be explained on the basis of scientific principles. The founding of the Society for Psychical Research in 1882 in London marked the beginning of an organized and coordinated research by experts in the sciences and humanities to discover the truth of these 'para-normal' matters; six years later a similar society was founded in the United States. Currently such research societies exist in many parts of the world. Psychical research, the scientific study of para-normal events, is also conducted at a number of leading universities.
Parapsychology developed from psychical research and includes investigations of the possibility of life after death. Such topics were formerly considered inappropriate for psychological study.
The greater part of the research undertaken has involved testing people for ESP ability. There are three types of ESP: clairvoyance, which involves obtaining knowledge of objects and events by para-normal means; telepathy, which is a capacity to know the thoughts and emotions of another person; and precognition, which is the ability to predict future events. During the past 50 years scientists have developed experimental means of testing these abilities.
The American Joseph Banks Rhine, who conducted extensive research at Duke University from the 1930s to 1960s, is probably best known for his attempts to refine these tests. He and his co-workers used Zener cards, named after the psychologist Karl E. Zener, which consisted of a pack of 25 cards bearing five symbols (cross, star, circle, wave and rectangle). The cards were shuffled by the experimenter and the person to be tested had to determine the order of the cards (which indicated clairvoyance) or identify each card in turn as the experimenter looked at it (which determined telepathy).
Probability alone, it was felt, should yield five correct guesses out of 25. A person who correctly made seven or eight calls was considered to have some ESP ability.
Test results have shown that people vary widely in ESP capacity and that few have great ability. Some experiments suggest that ESP ability 'comes and goes'; that is, a person may at times demonstrate high ability and at others only chance results.
Fewer experimental tests of psychokinesis have so far been made. There has been some research into the ability of a person to cause a certain number on a dice to appear but no consistently high-scoring people have been found. Some individuals appear to be able to bend metal objects, such as spoons and keys, but these occurrences are considered to be scientifically controversial. There is a long history of naturally occurring psychokinetic events produced by agents called poltergeists but these events have never been scientifically substantiated.
Poltergeists were considered to 'plague' a house and cause furniture to move, objects to travel across rooms and windows to break but seldom were regarded as causing physical injury to people.
To date there has been little research into the causes of and reasons for parapsychological phenomena. This appears to be due to scientific scepticism about the existence of such phenomena, which has caused researchers to concentrate on simply verifying them. Many scientists still continue to reject the methods and findings of psychical researchers, although a growing number considers para-normal events to be unproved possibilities rather than complete impossibilities.