Parapsychology or psychic research is the scientific study of Extrasensory Perception (ESP). ESP is sometimes described as a superset within which clairvoyance, telepathy, and precognition are subsets: clairvoyance being an ESP response to an object or event; telepathy, an ESP response to a feeling or thought; and precognition, an ESP response to a future event. The most important basic finding about ESP is that it occurs, that extrachance response to stimuli has been demonstrated under conditions that preclude sensing, remembering, or inferring the stimuli. ESP does not seem to relate to spatial or temporal separation, to electromagnetic radiation, to target size, or to any other physical variable. When statistical criticism was offered in the very early days of research, parapsychologists turned to professional statisticians for advice, and now there is general agreement that the standard statistical analyses are correct.