Telepathy moved from anecdote to laboratory with J. B. Rhine at Duke University in the early 1930s, whose card-guessing trials using Zener cards, a deck of five simple symbols, aimed to generate a statistic rather than a story. Rhine's early results beat chance by wide margins, and his 1934 book Extrasensory Perception popularised the term. The results did not survive scrutiny.
Critics documented sensory leakage: subjects could sometimes see a card's back-imprint, catch a reflection in glass or an experimenter's eyes, or pick up unconscious auditory cues, and W. S. Cox's attempted replication at Princeton, over twenty five thousand trials, found no effect at all. The debate shifted in the 1970s to the ganzfeld protocol, which pairs mild sensory deprivation in a "receiver" with an isolated "sender" concentrating on a randomly chosen image.
Charles Honorton reported a positive pooled effect across ganzfeld studies; Ray Hyman, reviewing the same data, argued flaws in randomisation and selective reporting could explain it. Their 1986 joint communique agreed the results were not simple chance or fraud but disagreed on what they meant, and called for tighter, automated protocols. Honorton's subsequent autoganzfeld series used computer-controlled randomisation and again reported above-chance scoring, but later large-scale replications, including a well-powered set run in the 2000s, did not confirm the effect at a level independent labs accept as established. No telepathy protocol has yet cleared the bar parapsychology itself set in 1986: consistent, blind, independently replicated results.