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.
Belief in precognition has been related to superstition. A 1978 Gallup poll found that 37% of Americans surveyed believed in precognition. According to psychologists Tobacyk and Milford, belief in precognition was greater in college women than in men, and a 2007 Gallup poll found that women were more prone to superstitious beliefs in general.
In the early 20th century 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.
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. Rhine's experiments were discredited due to the discovery that sensory leakage or cheating could account for all his results such as the subject being able to read the symbols from the back of the cards and being able to see and hear the experimenter to note subtle clues.
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.
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.
"Feeling the Future" controversy
In 2011, the parapsychologist Daryl Bem published the article "Feeling the Future: Experimental Evidence for Anomalous Retroactive Influences on Cognition and Affect" in the Journal of Personality and Social Psychology that offered statistical evidence for precognition. The article's findings challenged modern scientific conceptions about the unidirectional nature of time. Its presentation by a respected researcher and its publication by an upper tier journal engendered much controversy. In addition to criticism of the paper itself, the paper's publication prompted a wider debate on the validity of peer review process for allowing such a paper to be published. Bem appeared on MSNBC and The Colbert Report to discuss the experiment.
Jeffrey Rouder and Richard Morey who applied a meta-analytical Bayes factor to Bem's data concluded "We remain unconvinced of the viability of ESP. There is no plausible mechanism for it, and it seems contradicted by well-substantiated theories in both physics and biology. Against this background, a change in odds of 40 is negligible.
After evaluating Bem's nine experiments, psychologist James Alcock said that he found metaphorical "dirty test tubes," or serious methodological flaws, such as changing the procedures partway through the experiments and combining results of tests with different chances of significance. It is unknown how many tests were actually performed, nor is there an explanation of how it was determined that participants had "settled down" after seeing erotic images. Alcock concludes that almost everything that could go wrong with Bem's experiments did go wrong. Bem's response to Alcock's critique appeared online at the Skeptical Inquirer website and Alcock replied to these comments in a third article at the same website.
In 2012, the same journal that published Bem's original experiments, the Journal of Personality and Social Psychology (Vol. 103, No. 6), published “Correcting the Past: Failures to Replicate Psi” by Jeff Galek of Carnegie Mellon University, Robyn A. LeBoeuf of the University of Florida, Leif D. Nelson of the University of California at Berkeley, and Joseph P. Simmons of the University of Pennsylvania. The paper reported seven experiments testing for precognition that "found no evidence supporting its existence.”
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."
According to Special Relativity, Superluminal communication, or communication faster than the speed of light, would be the same as communication backwards through time. The hypothetical name for a particle which always moves faster than the speed of light is the Tachyon. A number of theories allowing particles or information to travel backward in time, retrocausality in physics, have been proposed by prominent scientists or have received meaningful evaluation by the scientific community.    
Various psychological processes have been offered to explain experiences of apparent precognition. These include:
- Selection bias where people remember the "hits" and forget the "misses", remember coincidences more often than other non-coincidences, or when they were correct about a future event rather than instances when they were wrong. Examples include thinking of a specific person before that person calls on the phone. Human memory, it is argued, has a tendency to record instances when the guess was correct, and to dismiss instances when the guess was incorrect.
- Unconscious perception by which people unconsciously infer, from data they have unconsciously learned, that a certain event will probably happen in a certain context. As with cryptomnesia, when the event occurs, the former knowledge appears to have been acquired without the aid of recognized channels of information.
- Self-fulfilling prophecy and Unconscious enactment in which people bring events that they have precognized to pass, but without their conscious knowledge.
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.
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.
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, 300 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.
Suppose that you can remember ten incidents from a night's dreaming, at least when prompted by a similar incident occurring a day. Now consider how many incidents occur during a day, including those you read about in the paper, watch on television or hear from your friends. There are a vast number and it is highly probable that from time to time one of them will, at least to some extent, resemble one of those from your dreams. When one or more of these coincidences occur, people are likely to conclude that dreams foretell the future.
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."
- Déjà vu
- Premonition (film)
- Premonitions (novel)
- Second sight
- Veridical dream
- List of topics characterized as pseudoscience
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- Stenger, Victor. (1990). Physics and Psychics: The Search for a World Beyond the Senses. Prometheus Books. p. 166. ISBN 0-87975-575-X "The bottom line is simple: science is based on consensus, and at present a scientific consensus that psychic phenomena exist is still not established."
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- Harold Gulliksen. (1938). Extra-Sensory Perception: What Is It?. American Journal of Sociology. Vol. 43, No. 4. pp. 623-634. "Investigating Rhine's methods, we find that his mathematical methods are wrong and that the effect of this error would in some cases be negligible and in others very marked. We find that many of his experiments were set up in a manner which would tend to increase, instead of to diminish, the possibility of systematic clerical errors; and lastly, that the ESP cards can be read from the back."
- Charles M. Wynn, Arthur W. Wiggins. (2001). Quantum Leaps in the Wrong Direction: Where Real Science Ends...and Pseudoscience Begins. Joseph Henry Press. p. 156. ISBN 978-0-309-07309-7 "In 1940, Rhine coauthored a book, Extrasensory Perception After Sixty Years in which he suggested that something more than mere guess work was involved in his experiments. He was right! It is now known that the experiments conducted in his laboratory contained serious methodological flaws. Tests often took place with minimal or no screening between the subject and the person administering the test. Subjects could see the backs of cards that were later discovered to be so cheaply printed that a faint outline of the symbol could be seen. Furthermore, in face-to-face tests, subjects could see card faces reflected in the tester’s eyeglasses or cornea. They were even able to (consciously or unconsciously) pick up clues from the tester’s facial expression and voice inflection. In addition, an observant subject could identify the cards by certain irregularities like warped edges, spots on the backs, or design imperfections."
- Terence Hines. (2003). Pseudoscience and the Paranormal. Prometheus Books. p. 122. ISBN 1-57392-979-4 "The procedural errors in the Rhine experiments have been extremely damaging to his claims to have demonstrated the existence of ESP. Equally damaging has been the fact that the results have not replicated when the experiments have been conducted in other laboratories."
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- Betty Markwick. (1985). The establishment of data manipulation in the Soal-Shackleton experiments. In Paul Kurtz. A Skeptic’s Handbook of Parapsychology. Prometheus Books. pp. 287-312. ISBN 0-87975-300-5
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- James Alcock, Back from the Future: Parapsychology and the Bem Affair, March/April 2011 Skeptical Inquirer, January 6, 2011.
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- "In short, you have lots of dreams and encounter lots of events. Most of the time the dreams are unrelated to the events, and so you forget about them. However, once in a while one of the dreams will correspond to one of the events. Once this happens, it is suddenly easy to remember the dream and convince yourself that it has magically predicted the future. In reality, it is just the laws of probability at work."
- "The principle is known as the ‘Law of Large Numbers’, and states that unusual events are likely to happen when there are lots of opportunities for that event. It is exactly the same with any national lottery. The chances of any one person hitting the jackpot is millions to one, but still it happens as regular as clockwork each week because such a large number of people buy tickets. For genuine evidence of premonitions then, the situation is even worse than we have imagined... Given that people dream about doom and gloom more often than not, the numbers quickly stack up and acts of apparent prophecy are inevitable."
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