Parapsychology is the study of psychic phenomena, i.e. the exchange of information or some other interaction between an organism and its environment, without the mediation of the senses. This includes mind to mind communication (paranormal cognition) such as telepathy and movement of (or influence on) matter by mind (paranormal action) which is referred to by parapsychologists as psychokinesis.
Psi phenomena have been reported since the earliest times, from biblical miracles and the Delphic oracle, through medieval witches, to nineteenth-century spiritualism and twentieth-century spoonbending. Psychic powers are claimed in every culture whether by shaman, rain maker, voodoo practitioner or faith healer. Along with religious belief and drug taking, psychic experiences seem to be universal.
The field of parapsychology takes four main groups of phenomena as its subject matter: extrasensory perception, psychokinesis, anomalous experience and apparitional phenomena. Examples of each follow:
Extrasensory perception (ESP)
Macro-PK (visible effects), e.g. metal bending, apports
Micro-PK (statistically measurable non-visible effects), e.g. random number generator (RNG) effects
Direct mental interaction with living systems (DMILS), e.g. on electrodermal activity