Ganzfeld experiment

The Ganzfeld experiment is a pseudoscientific technique used by advocates of parapsychology to test persons for so-called extrasensory perception (ESP).

Experimental conditions
In this "experiment", a person wearing headphones is placed in a room in relaxed mood half-lying in a comfortable chair. Halved ping-pong balls are placed over his/her eyes with red light shone on them. This makes quite striking imagery for pseudoscience documentaries and is presumably only for this purpose. In the course of the "experiment", a "sender" sends information about an object ("target") to the "receiver" (the person) and the "receiver" tell what he/she is seeing. At the end of this process, the "experimenter" shows the "receiver" some possible "targets" from which he/she decides which resembled the image he/she saw during the "experiment".

Studies
The psychologist Ray Hyman (1985) reviewed forty-two studies from the ganzfeld experiment and concluded "I believe that the ganzfeld psi data base, despite initial impressions, is inadequate either to support the contention of a repeatable study or to demonstrate the reality of psi. Whatever other value these studies may have for the parapsychological community, they have too many weaknesses to serve as the basis for confronting the rest of the scientific community". According to Terence Hines in his book Pseudoscience and the Paranormal (2003):

Hyman (1985) found several different flaws in the ganzfeld studies. There was inadequate randomization of the targets in a large percentage of the studies. Opportunities for information on the target to inadvertently reach the subject and breaches in security that might have permitted cheating were also present in many of the studies. Many studies were not described in sufficient detail to allow evaluation of what actually happened in the study. Statistical problems were also common. These included the use of incorrect statistical tests and procedures and “multiple testing” errors in which the subjects’ responses were tested several times against chance, using different criteria for scoring the responses for different tests. This, like testing numerous astrological predictions or numerous predictions of any theory, increases the chance of spuriously obtaining a significant result. Further, the greater the number of flaws in a study, the more likely it was to find a significant effect. This is another example of the phenomenon noted earlier, that evidence for ESP and related phenomena disappears as the tightness of experimental controls is increased. On the basis of Hyman’s review, the ganzfeld studies cannot be said to provide evidence for ESP, as claimed by proponents.

The ganzfeld studies contained serious flaws such as inadequate randomization; sensory leakage (in some cases, the receivers could hear what was going on in the sender's room next door and, it was possible for the sender's fingerprints to be visible on the target object for the receiver to see); and inappropriate statistical analysis. Parapsychologists were embarrassed over this issue.

In response, the parapsychologist Charles Honorton co-wrote a paper in 1986 with Hyman that called for additional studies with better, more precise methodologies that would help rule out nonparanormal sources of above-chance results. Daryl Bem and Honorton (1994) published a review of ganzfield studies and concluded they were evidence for ESP. But it turned out that there was a serious problem with their review.

The psychologists Julie Milton and Richard Wiseman (1999) published a critique of that review and an analysis of additional new ganzfeld studies. They discovered that Bem and Honorton had counted the results of some studies as being statistically significant when they actually were not significant. This error led Bem and Honorton to conclude that the studies they reviewed had shown, overall, that ESP was operating in the ganzfeld. Milton and Wiseman reviewed thirty ganzfeld studies and they showed no effect greater than chance. Milton and Wiseman concluded:

The new ganzfeld studies show a near-zero effect size and a statistically nonsignificant overall cumulation... The autoganzfeld results have not been replicated by a "broader range of researchers." The ganzfeld paradigm cannot at present be seen as constituting strong evidence for psychic functioning.

Pseudoscientific experiments in parapsychology such as the ganzfeld studies are not evidence for psi. Consistent, independent replication has not been achieved.

Usual outcome
In reality, the entire "experiment" is a trick. The "experiment" is not always done in a soundproof room. The "receiver" and the "experimenter" can easily hear when videos were playing during the "experiment". Involuntary cues are given to the "receiver" during the selection procedure.