An Introduction to the Ganzfeld


The ganzfeld (from the German meaning whole field) technique was first used in parapsychology by three investigators - William Braud, Chuck Honorton and Adrian Parker - all of whom were working independently of each other. It is based on the principle of perceptual deprivation, i.e. eliminating sources of patterned or meaningful stimulation from the external environment which previous psychological experimentation had found to increase the amount of mental imagery experienced by participants. As mental imagery is a frequent vehicle for conveying possible psychic impressions to people, it was thought that this technique might prove useful in parapsychological research.

As used in psi experiments, there are basically four main aspects to the Ganzfeld procedure. Click on the desired area for more details.





The Experimenter's role in a Ganzfeld experiment


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oo The experimenter's room is adjacent to the receiver's, and has a two-way audio link, enabling the experimenter to hear and talk to the receiver. However, they have no communication with the sender and remain unaware of what the target for that session is until the session is over.

oo The experimenter has access to the equipment that controls the audiovisual presentation, although as most of the procedure is under computer control, their main role is to note down the receiver's reported mentation.


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The Receiver's role in a Ganzfeld experiment


oo The receiver is located in an isolated room, having contact only with the experimenter via a two-way audio link. This room is a double-walled, double-doored room, providing very good acoustical shielding (link for technical details). No sound or vibration can be heard or felt in the receiver's room that originated from the sender's room.

oo To remove patterned visual stimulation, translucent acetate hemispheres (aka halved table-tennis balls!) are placed over the receiver's eyes. A soft red light is then shone on them. Receivers are asked to keep their eyes open when wearing the shields, which provides them with a homogeneous visual field.

Image of the receiver

oo Patterned auditory stimulation is avoided by playing white noise (something like soft radio static) through headphones.

oo Tactile stimulation is reduced by having the receiver recline in a comfortable chair and perform relaxation exercise to reduce muscular tension.

oo The receiver remains in the Ganzfeld setting for about 30 minutes, reporting via a microphone, any mental imagery, thoughts or bodily sensations that they experience.

oo After the impression period, the experimenter reviews the receiver's impressions with them, to remind them of their experiences.

oo The receiver then removes their eye shields and is shown via a monitor four possible targets, one of which is a duplicate of the actual target for the session and the other three being decoys. The receiver and/or an independent judge ranks or rates each of the four targets according to the degree of similarity to the impressions. A successful session is when the actual target receives the highest rating/ranking.

oo As there is a one out of four chance of "guessing" the right target by chance alone (i.e. 25%), a successful study is one in which the correct target was chosen significantly more often than 25% of the time.


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The selection of the target in a Ganzfeld experiment


oo The target is selected by the controlling compter program using a pseudo-random algorithm (the Edinburgh set-up uses the rnd function in MS-DOS Quick Basic).

oo There is a pool of possible target sets, each containing 4 video clips selected to be as dissimilar as possible. The computer selects one pool, then one particular clip within that pool to be the target.

oo The video player is housed in a seperate also acoustically shielded room. This ensures that not even the experimenter will be able to guess the target by picking up on as subtle a clue as how far the tape fast forwards before playing the video clip!

oo Two identical video tapes and players are used, one of which plays the target clip to the sender, the other which plays the four possible clips (the target plus 3 decoys) to the receiver. This ensures that suble cues due to tape wear are not given to the receiver.


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The Sender's role in a Ganzfeld experiment


oo The sender is in a room distant from both the receiver and the experimenter.

Image of the sender

oo The sender watches a repeating video clip on a television monitor, with the sound being played through headphones. The intent is to somehow relay the information contained in, and the feelings associated with, the video clip to the receiver.

oo Although the sender can hear what the receiver says, which allows them to modify their "sending strategy" if necessary, there is no outward link. The sender is completely isolated and cannot communicate with any other person dring the experiment.


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Authors: Paul Stevens, Deborah Delanoy and Kathy Dalton.
Last modified 25th. January 1995