page_title: Sensory leakage
section_title: Ganzfeld experiment
hierarchical_section_title: Sensory leakage / Ganzfeld experiment
caption_attribution_description: English: Example of a subject in a Ganzfeld experiment.
context_page_description: Sensory leakage is a term used to refer to information that transferred to a person by conventional means during an experiment into psi.
  For example, where the subject in an ESP experiment receives a visual cue — the reflection of a Zener card in the holder's glasses — sensory leakage can be said to have occurred.
context_section_description: The ganzfeld experiment studies that were examined by Ray Hyman and Charles Honorton had methodological problems that were well documented. Honorton reported only 36% of the studies used duplicate target sets of pictures to avoid handling cues. Hyman discovered flaws in all of the 42 ganzfeld experiments and to assess each experiment, he devised a set of 12 categories of flaws. Six of these concerned statistical defects, the other six covered procedural flaws such as inadequate documentation, randomization and security as well as possibilities of sensory leakage. Over half of the studies failed to safeguard against sensory leakage and all of the studies contained at least one of the 12 flaws. Because of the flaws, Honorton agreed with Hyman the 42 ganzfeld studies could not support the claim for the existence of psi.
  Possibilities of sensory leakage in the ganzfeld experiments included the receivers hearing what was going on in the sender's room next door as the rooms were not soundproof and the sender's fingerprints to be visible on the target object for the receiver to see.
  Hyman also reviewed the autoganzfeld experiments and discovered a pattern in the data that implied a visual cue may have taken place:
  The most suspicious pattern was the fact that the hit rate for a given target increased with the frequency of occurrence of that target in the experiment. The hit rate for the targets that occurred only once was right at the chance expectation of 25%. For targets that appeared twice the hit rate crept up to 28%. For those that occurred three times it was 38%, and for those targets that occurred six or more times, the hit rate was 52%. Each time a videotape is played its quality can degrade. It is plausible then, that when a frequently used clip is the target for a given session, it may be physically distinguishable from the other three decoy clips that are presented to the subject for judging. Surprisingly, the parapsychological community has not taken this finding seriously. They still include the autoganzfeld series in their meta-analyses and treat it as convincing evidence for the reality of psi.
  Hyman wrote the autoganzfeld experiments were flawed because they did not preclude the possibility of sensory leakage.
caption: Participant in a ganzfeld telepathy experiment
exif: {}