Parapsychology applies the ordinary tools of experimental psychology, controlled conditions, randomization, blinding, and statistical analysis, to claims that fall outside the phenomena mainstream psychology and physics currently recognize: telepathy, or mind-to-mind communication; clairvoyance, perceiving information without any known sensory channel; precognition, knowing future events in advance; psychokinesis, affecting physical systems by intention alone; and a wider set of related claims including near-death and out-of-body experiences, apparitions, mediumship, and poltergeist activity. Researchers in the field generally do not start from the assumption that these phenomena are real; the field's stated purpose, since its founding, has been to determine through controlled testing whether any of them can be demonstrated reliably, and serious parapsychologists have themselves debunked specific claims and mediums found to be using fraud or sensory leakage.
Its core experimental tool has been the forced-choice or free-response guessing task: a subject attempts to identify a hidden target, a card, an image, or a future random event, under conditions designed to rule out sensory cues. The best known protocol, developed from the 1970s, is the ganzfeld procedure, in which a receiver in mild sensory deprivation attempts to identify an image a separated sender is concentrating on; pooled results across decades of ganzfeld studies have shown a small statistical departure from chance that proponents read as evidence of an anomalous effect and skeptics read as an artifact of selective reporting or weak blinding, a dispute never fully resolved.