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In parapsychology, precognition (from the Latin præ-, "before" and cognitio, "acquiring knowledge"), also called future sight, and second sight, is a type of extrasensory perception that would involve the acquisition or effect of future information that cannot be deduced from presently available and normally acquired sense-based information.
Scientific investigation of extrasensory perception (ESP) is complicated by the definition which implies that the phenomena go against established principles of science. Specifically, precognition would violate the principle that an effect cannot occur before its cause. There are established biases affecting human memory and judgment of probability that create convincing but false impressions of precognition.
There are a number of organizations which collect self-reported "psychic" experiences from the public at large. Classifications of these (self-reported) experiences by type provide a sense of the prevalence of belief in particular kinds of parapsychological phenomena in the public at large.
In the particular case of precognition, belief is widespread. In one review of a U.S. case collection, Duke University's Parapsychology Laboratory surveyed the public and collected 1777 dream-based and 1513 wakeful reports of personal parapsychological experiences, of which participants categorized 75% of the sleeping and 60% of the wakeful experiences as precognitive, respectively. A similar distribution was identified for a separate collection of 157 cases reported by children; here, the children categorized the majority of their personal experiences as precognitive dreams (52%), followed by precognitive intuitions. A German case collection produced a similar figure: 52% of 1,000 cases were categorized as precognitive. A similar British study of 300 cases showed volunteers categorizing 34% as precognitive.
The mainstream scientific community does not take public belief in precognition (or any other phenomenon) as evidence for its veracity or even credibility, though widespread reports of interesting phenomena might inspire scientific inquiry. Such inquiries are conducted using the scientific method, and the evidence collected in such methodological studies is used to determine the credibility of precognition and other psychic phenomena.
History records many instances of apparent precognition (see Ides of March), and belief in its occurrence as a form of seeing into the future (this can be through visions, déjà vu or through dreams which is usually the cause of recognition). The first thorough collection and critical review of such spontaneous cases was created by the British Society for Psychical Research (SPR). Reports of these cases were authored by Eleanor Sidgwick in 1888, and Herbert Saltmarsh in 1938. Sidgwick believed the evidence warranted further investigation as to the validity of the concept of precognition, and Saltmarsh offered that the evidence, if it did not scientifically establish the phenomenon, at least excluded alternative hypotheses. Nicol, however, in a later review, came to the conclusion that their evidence was not so suggestive, given, in particular, the long length of time between the occurrence of some of the most suggestive cases, and their first report to the SPR.
J. W. Dunne, a British aeronautics engineer, recorded each of his dreams as they occurred to him, identifying any correspondences between his future experiences and his recorded dreams. In 1927, he reported his findings, in An Experiment with Time. In this work, at least 10% of his dreams appeared to represent some future event, pertaining to some relatively trivial incident in Dunne's own life, or some major news events appearing in the press a day or so after the dream. Dunne concluded that precognitive dreams are common occurrences: many people have them without realizing it, largely because they do not recall the details of the dream. Also reported in the book was an experiment Dunne conducted with several other people who studiously recorded their dreams and sought to associate them with subsequent experiences. Dunne felt these confirmed his claims, but a 1933 independent experiment failed to replicate his findings.
With free-response methods, experiments have been conducted in precognitive dreaming at the sleep laboratory of the Maimonides Medical Center, in precognitive Ganzfeld hallucinations and visions. While such experiments have produced some suggestive evidence for precognition, they have been somewhat limited to studies of selected participants, and have involved procedures that can be too expensive for other researchers to replicate, or too complex to theoretically interpret.
The first such ongoing and organized research program on precognition was instituted by J. B. Rhine in the 1930s at Duke University's Parapsychology Laboratory. Rhine used a method of forced-choice matching in which participants recorded their guesses as to the order of a deck of 25 cards, each five of which bore one of five geometrical symbols. The test of precognition was based on the fact that these "guesses" were made before the deck was shuffled by the experimenter. In an effort to distinguish between different parapsychological accounts of precognition, and to better understand its conditions, experiments were conducted in which the order of the target deck of cards was determined by hand versus machine, or by reference to macroscopic events, such as randomly selected meteorological readings, or by complex algorithms. Early experiments also sought to determine the temporal scope of precognition by organizing the target deck only 1-2 versus 10 days, or even a year, after responses had been recorded and secured.
Experiments by Samuel G. Soal ran forced-choice ESP experiments in which someone attempted to identify which of five animal pictures a subject in another room was looking at. Their performance on this task was at chance, but when the scores were matched with the card that came after the target card, three of the thirteen subjects showed a very high hit rate. Rhine described Soal's work as "a milestone in the field". Research chemist George Price who reviewed Soal and Bateman's book Modern Experiments in Telepathy for the journal Science in 1955. It was suggested that the positive results not attributable to error were more likely the result of deliberate fraud. This prompted several replies that Price's criticism was unfair, resting on the mere possibility of fraud rather than actual proof. In 1978, the experiments were exposed as fraudulent. The statistician and paragnost Betty Markwick, while seeking to vindicate Soal, discovered that he had altered his data to create all the extra hits and give the study its statistical significance. The untainted experimental results showed no evidence of precognition in the hits or the ratios.
Other researchers, including Smithsonian Executive Secretary Charles Greeley Abbot and British psychologist R. H. Thouless, introduced the study of precognition in the displacement of guesses to targets. This involved a set of target symbols, and "guesses" as to their identity, but, rather than precognizing the order of a whole deck of symbols, scored for precognition by checking the correspondence between each response and the target assigned to one or more trials ahead of that to which the response was originally assigned. Several studies using this method have continually offered displacement as reliable evidence for precognition.
Following these experiments, a more automated technique of experimentation was introduced that did not rely on hand-scoring of equivalence between targets and guesses, and in which the targets could be more reliably and readily tested as random. This involved testing for precognition with the use of high-speed random event generators (REG), as introduced by Helmut Schmidt in 1969 and further conducted, in particular, at the Princeton Engineering Anomalies Research Lab (1979–2007). The psychologist C. E. M. Hansel found flaws in all of Schmidt's experiments into precognition. Hansel found that necessary precautions were not taken, there was no presence of an observer or second-experimenter in any of the experiments, no counterchecking of the records and no separate machines used for high and low score attempts.
The physicist John Taylor has written "since only positive energies are possible, particles going backward in time cannot exist. Any claim that they do is purely a fantasy in the mind of the parapsychologist. There is therefore no direct justification for precognition from physics... experimental evidence from high energy physics is strongly against it."
Various psychological processes have been offered to explain experiences of apparent precognition. These include:
Some psychologists have explained the apparent prevalence of precognitive dreams in terms of memory biases, namely a selective memory for accurate predictions and distorted memory so that dreams are retrospectively fitted onto subsequent events. In one experiment, subjects were asked to write down their dreams in a diary. This prevented the selective memory effect, and the dreams no longer seemed accurate about the future. Another experiment gave subjects a fake diary of a student with apparently precognitive dreams. This diary described events from the person's life, as well as some predictive dreams and some non-predictive dreams. When subjects were asked to recall the dreams they had read, they remembered more of the successful predictions than unsuccessful ones.
Precognition is considered hallucination by mainstream psychiatry.
An early inquiry into this phenomenon was done by Aristotle in his On Divination in Sleep. His criticism of these claims appeals to the fact that "the sender of such dreams should be God", and "the fact that those to whom he sends them are not the best and wisest, but merely commonplace persons." Thus: "Most [so-called prophetic] dreams are, however, to be classed as mere coincidences...", here "coincidence" being defined by Aristotle as that which does not take "place according to a universal or general rule" and referring to things which are not of themselves by necessity causally connected. His example being taking a walk during an eclipse, neither the walk nor the eclipse being apparently causally connected and so only by "coincidence" do they occur simultaneously.
Louisa Rhine at the Parapsychology Laboratory at Duke University compiled the best-known and largest body of dream evidence. Dr. Rhine collected over 7000 accounts of ESP experiences. The majority of these accounts were dream related and were seemingly precognitive in nature. The material for this work was collected by advertisements in various well-known popular media.
In 1932 Charles Lindbergh's infant son was kidnapped and murdered. The psychologists Henry Murray and D. R. Wheeler tested precognitive dreams by inviting the public to report any dreams of the child. A total of 1, 300 dreams were reported. Only five percent envisioned the child dead and only 4 of the 1, 3000 envisioned the location of the body buried amongst trees. This number was no better than chance.
David Ryback, a psychologist in Atlanta, used a questionnaire survey approach to investigate precognitive dreaming in college students. His survey of over 433 participants showed that 290 or 66.9 percent reported some form of paranormal dream. He rejected many of these claims and reached a conclusion that 8.8 percent of the population was having actual precognitive dreams.
Dreams which appear to be precognitive may in fact be the result of the Law of large numbers. Robert Todd Carroll, author of The Skeptic's Dictionary put it this way: "Say the odds are a million to one that when a person has a dream of an airplane crash, there is an airplane crash the next day. With 6 billion people having an average of 250 dream themes each per night, there should be about 1.5 million people a day who have dreams that seem clairvoyant."