A ganzfeld experiment is an assessment used by parapsychologists that they contend can test for extrasensory perception (ESP) or telepathy. In these experiments, a "sender" attempts to mentally transmit an image to a "receiver" who is in a state of sensory deprivation. The receiver is normally asked to choose between a limited number of options for what the transmission was supposed to be and parapsychologists who propose that such telepathy is possible argue that rates of success above the expectation from randomness are evidence for ESP. Consistent, independent replication of ganzfeld experiments has not been achieved, and, in spite of strenuous arguments by parapsychologists to the contrary, there is no validated evidence accepted by the wider scientific community for the existence of any parapsychological phenomena. Ongoing parapsychology research using ganzfeld experiments has been criticized by independent reviewers as having the hallmarks of pseudoscience.

Telepathy is the purported vicarious transmission of information from one person's mind to another's without using any known human sensory channels or physical interaction. The term was first coined in 1882 by the classical scholar Frederic W. H. Myers, a founder of the Society for Psychical Research (SPR), and has remained more popular than the earlier expression thought-transference.