INTRODUCTION

Parapsychology, also known as psychical research, the investigation of alleged phenomena and abilities that apparently cannot be explained by conventional scientific theories.

Parapsychologists divide paranormal phenomena into two classes. Extrasensory perception (ESP) is defined as the ability to acquire information without the use of the senses, and includes telepathy (when the information comes from another person); clairvoyance (when the information comes from a distant object or event); and precognition (when the information is about the future).

 Psychokinesis (PK) is the supposed ability to influence distant objects or events without using known physical forces; this is divided into macro-PK (for example, moving large objects or bending spoons) and micro-PK (for example, influencing computer systems or random number generators). "Psi" is a general term covering them all.

Also studied are ghosts, poltergeists (sometimes considered as a form of PK), apparitions of the dying or dead, mediumship, and out-of-body experiences (in which people feel as though they have left their bodies and can see and move without them).

 Parapsychologists tend to concentrate on ESP and PK, and more often carry out laboratory experiments, while psychical researchers tend to concentrate on spontaneous cases and phenomena suggestive of human survival after death.

HISTORY OF PSYCHICAL RESEARCH

Spiritualism, which began in the 1840s in North America, was the foundation for psychical research. Spiritualist mediums claimed to contact the spirits of the dead through mental mediumship (conveying messages from the "other side", often in a trance state) and physical phenomena (such as table-tapping or tilting, levitation, and writing on closed slates). It was claimed that a materialized spirit, made from a substance which acquired the term ectoplasm, exuded from the medium's body.

Since these phenomena appeared to challenge the laws of physics, some scientists tried to test them. Michael Faraday experimented with table-tilting; in 1853 he concluded that it was due entirely to unconscious muscular action by the sitters. William Crookes took photographs of the full-body materializations created by the medium Florence Cook and studied the medium Daniel Dunglas Home, who it was claimed could levitate heavy tables and play musical instruments without touching them. Crookes believed these phenomena implied a new form of energy—although others pointed out that fake mediums shared techniques, and sold special apparatus for tricking observers.

In 1882 the Society for Psychical Research (SPR) was founded "to examine without prejudice or prepossession and in a scientific spirit those faculties of man, real or supposed, which appear to be inexplicable on any generally recognized hypothesis". Eminent scholars among the founders were Edmund Gurney, Frederick Myers, and Henry Sidgwick, who was Fellow of Trinity College, Cambridge, and the society's first president. They established committees to investigate thought transference (now known as telepathy); mesmerism (or hypnosis); apparitions and haunted houses; and the physical phenomenon of mediumship.

In 1886 the Census of Hallucinations was published. Some 17,000 people were asked whether they had ever seen or felt anything, or heard a voice, that was not due to any physical cause.

Of special interest were hallucinations of a dead person experienced by people within 12 hours either way of the person's death. These were claimed to occur far more often than expected by chance and to be evidence for some form of communication with the dying.

Experiments on thought transference also began around this time. In some an "agent" would draw a picture and a "percipient" would try to reproduce it. Although impressive results were obtained, it was and is difficult to control chance factors and prior expectations in such experiments, making any conclusions unreliable.

Later experiments used playing cards or numbers as targets. This meant that statistical methods for evaluating the results could be developed, which laid the foundation for modern experiments in parapsychology.

Psychical research continues to this day; both the SPR in London and the American SPR (founded in 1885) are still active.

FOUNDATIONS OF PARAPSYCHOLOGY

In the 1930s, at Duke University in North Carolina, J. B. Rhine and his wife Louisa tried to transform 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)—but 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 PK and also claimed results that were better than chance.

Rhine's controversial book, Extrasensory Perception After Sixty Years (1940), led others to criticize his methods and to try to repeat his findings. Most failed, including the London mathematician Samuel Soal, who tried for five years without success.

Eventually he re-analysed many of his results and found that one subject was apparently performing precognition. In the early 1950s, further tests with this subject, under tightly controlled conditions, gave statistically significant results—convincing many people that Rhine was right. Accusations and counter-claims abounded until, in 1978, it was finally proven that Soal had cheated and the results were worthless. However, many people had been convinced by these results for nearly 30 years.

Other parapsychologists found that some subjects scored below chance (psi-missing); scores tended to decline during testing (the "decline effect"); and people who believed in psi, called "sheep", scored better than those who did not believe in it ("goats")—which became known as the sheep-goat effect. However, none of these effects proved easy to replicate. In recent years parapsychologists have turned to other methods, notably free-response ESP tests and micro-PK

MODERN PARAPSYCHOLOGY

In the 1960s parapsychologists tested ESP in dreams, although the experiments were very time-consuming. In an attempt to get subjects into a relaxed state, and to cut off sensory input, the "ganzfeld" technique was adopted in the 1970s.

In a psi-ganzfeld experiment the receiver relaxes for 30 minutes or more with white noise playing through headphones, and with halved ping-pong balls taped over the eyes to provide a uniform visual field (the ganzfeld). Meanwhile, a sender looks at one of four pictures or videotapes in a distant room. After emerging from the ganzfeld the receiver is shown the four possible targets and asked which one most closely matches the ganzfeld experiences.

By 1985 many such experiments had been done and, in a much-publicized debate, parapsychologists used "meta-analysis", which pools the results of many experiments in an attempt to claim a consistent effect and a repeatable experiment. However, the critics pointed to experimental error, fraud, selective reporting of data, and non-random selection of targets as explanations. This issue has not been settled.

In remote viewing, one person travels to a randomly chosen distant location while another remains in the laboratory and tries to visualize the location.

As with ganzfeld, the subject or an independent judge then matches up the experiences with several possible locations. Early experiments, although successful, were criticized for allowing clues such as the weather to influence the results. In 1995 the American CIA released reports of more than 20 years of government research into remote viewing. They concluded that an effect had been demonstrated in the laboratory but that it was not useful for intelligence purposes.

PK research has been transformed by the use of computers. In a typical experiment a person tries to affect a random number generator (RNG). These are either random numbers produced by a computer algorithm (a sequence of steps used to solve a mathematical problem), or true random processes produced by, for example, radioactive decay.

If the RNG produces a string of 1s and 0s, the aim may be to produce more 1s, or more 0s. Over very large numbers of trials it is claimed that the numbers deviate slightly in the direction aimed at. Critics argue that the RNGs are not truly random, the trials not properly controlled, and the statistics wrongly applied.

Surveys show that over half the population believes in the paranormal. Some parapsychologists study the origins of these beliefs while others study psychic or other unexplained experiences.

However, some of these experiences, such as hallucinations, hypnosis and trance states, out-of-body and near-death experiences, and multiple personality—all of which used to be part of psychical research—are now more often studied by psychologists.

There is no general consensus about the existence of ESP and PK. Many claims have been made, and the research techniques greatly refined, but critics continue to have objections, and most scientists remain unconvinced.