Extra-sensory perception, or ESP, refers to the supposed ability to acquire information by some means other than the normal human senses, such as the traditional five senses of taste, sight, touch, smell, and hearing, or any of the other senses well known to science (balance, proprioception, etc).
Because the definition of sense is vague, the precise definition of extra-sensory is as well, but the term is generally meant to imply sources of information unknown to modern science. Despite the vagueness of the definition, no one has ever been documented by science as publicly or in a controlled experiment demonstrating ESP in a generally accepted way. The James Randi Educational Foundation offers $1 million to anyone who can demonstrate ESP or any psychic phenomenon. No one has ever collected.
Possible ESP phenomena include: telepathy, clairvoyance, precognition, retrocognition, medium-hood and séancing, psychometry, clairaudience, clairsentience, astral projection, the reading of auras and telekinesis. Study of these phenomena is known as parapsychology.
The word "psychic" is used as both a noun and adjective to denote a person capable of using ESP in any of its forms. Although most people who believe in ESP maintain that it is a power innate to only a relatively small percentage of the population, there are some who believe that everyone is psychic. These people claim that most of us have simply not learned yet to tap their innate extrasensory potential.
One problem with proving the existence or non-existence of extra-sensory perception is that if it exists it likely has a subtle rather than an overt effect. It is unlikely that someone can actually predict the future on demand, but that does not fully rule out that someone might be able to process some extra-sensory information occasionally. The existence or non-existence of subtle ESP may be impossible to empirically verify.
Another problem with proving the existence or non-existence of extra-sensory perception is that, if it exists, it is possibly a personal rather than an impersonal phenomenon. For example, sensing which playing card was drawn from a deck may not be possible, but that does not rule out the possibility of predicting whether a loved one was just involved in a car crash. The existence or non-existence of personalized ESP may be impossible to empirically verify.
It is obvious to science that there is a lot going on in the universe that is not registered consciously by the human senses. The universe is a complex interaction of electromagnetic and gravitational forces that seem to manifest as particles and/or waves. In fact, the universe is so complex that the senses of any animal must filter the external input in order to interact with its environment. For example, the human sense of sight does not directly see infrared or ultraviolet light even though many other animals' sense of sight allows them to see such light. The question then arises, are humans sensing such light and then subconsciously ignoring it or are they simply not equipped to sense it at all? Proponents of ESP suggest that there may be some "filters" within the human consciousness that can be shut down to allow more sensory data into the consciousness.
It has been said that people who claim to be psychic in one way or another fall into one of three categories: (1) genuine psychics, (2) frauds or hoaxers (people who use trickery or have fudged evidence that they are psychic) and (3) people who are not actually psychic but have fooled themselves into thinking they are, perhaps through a single anecdote, or by misjudging the likelihood that their predictions were better than coincidence would expect, or through the Forer effect. Many impostors from the second class use cold reading when performing their psychic readings, and some will even go through elaborate trickery with partners, as if performing a magic show.
When Franz Anton Mesmer and Grigori Rasputin were first popularizing hypnosis, the legend came about that a person who was hypnotized would be able to demonstrate ESP. Carl Sargent, a psychology major at Cambridge University, heard about the early claims of a hypnosis-ESP link, and designed an experiment to test whether they had any merit. He recruited forty fellow college students, none of whom identified him- or herself as having ESP, and then divided them into a group that would be hypnotized before being tested with a pack of 25 Zener cards, and a control group that would be tested with the same Zener cards. The control subjects averaged a score of 5 out of 25 right, exactly what chance would indicate. The subjects who were hypnotized did more than twice as well, averaging a score of 11.9 out of 25 right. Sargent's own interpretation of the experiment is that ESP is associated with a relaxed state of mind and a freer, more atavistic level of consciousness.
In the early days of radio and electronics, the technology seemed magical to most people, including the engineers working on it. It was suggested that the it might be used to unleash previously impossible feats of mental ability. This included communication with dead people, who were considered to have moved on to another world or "plane". Alec Reeves, one of the pioneers of digital communications, considered ESP a perfectly reasonable proposition. He believed that many of his inventions were prompted by the dead pioneer Michael Faraday, and spent much of his earlier years trying to perfect spiritualist telecommunication devices. Some of his experiments are available as ActiveXpages on his website.Difficulties with Establishing Extra-Sensory Perception
Possible Scientific Basis For Extra-Sensory Perception
Criticisms
Extra-Sensory Perception and Hypnosis
Extra-Sensory Perception and Technology