The Ganzfeld experiment - special issue: a tribute to Charles Honorton

Journal of Parapsychology, The, June, 1993 by Daryl J. Bem

Charles Honorton had three overriding scientific goals: understanding psi, providing parapsychology with a "recipe for replication," and winning mainstream acceptance for parapsychology. His chosen vehicle was the ganzfeld experiment. It is the jewel in the crown of Chuck Honorton's work and, arguably, the jewel in the crown of contemporary parapsychology itself.

In this article, I summarize the history of Chuck's ganzfeld work and then describe in more personal terms our collaborative efforts to bring it to the attention of mainstream psychology.

The Ganzfeld Procedure

Chuck left college in 1966 to work with J. B. Rhine at the Institute for Parapsychology in Durham. By that time, a number of parapsychologists were already searching for alternative laboratory procedures that would more faithfully reflect the circumstances that seemed to characterize reported instances of psi in everyday life.

Historically, psi has often been associated with meditation, hypnosis, dreaming, and other naturally occurring or deliberately induced altered states of consciousness. For example, the view that psi phenomena can occur during meditation is expressed in most classical texts on meditative techniques; the belief that hypnosis is a psi-conductive state dates all the way back to the days of early mesmerism (Dingwall, 1968); and cross-cultural surveys indicate that most reported "real-life" psi experiences are mediated through dreams (Green, 1960; Prasad & Stevenson, 1968; Rhine, 1962; Sannwald, 1959).

There is now experimental evidence consistent with these anecedotal observations: Several studies show that meditation facilitates psi performance (Honorton, 1977); a meta-analysis of experiments on hypnosis and psi suggests that hypnotic induction might also facilitate psi performance (Schechter, 1984); and the experiments conducted during the 1960s at Maimonides Medical Center in New York provided evidence for dream-mediated psi (Child, 1985; Ullman, Krippner, & Vaughan, 1973). (Honorton played an important role in these studies and subsequently served as Director of Research for the Maimonides laboratory from 1974 to 1979.)

These several lines of evidence converged to suggest a working model of psi in which psi-mediated information is conceptualized as a weak signal that is normally masked by internal somatic and external sensory "noise." By reducing ordinary sensory input, these diverse psi-conducive states are presumed to raise the signal-to-noise ratio, thereby enhancing a person's ability to detect the psi-mediated information (Honorton, 1969, 1977). To test the hypothesis that a reduction of sensory input itself facilitates psi performance, Chuck and others turned to the ganzfeld procedure (Braud, Wood, & Braud, 1975; Honorton & Harper, 1974; Parker, 1975), a procedure originally introduced into experimental psychology during the 1930s to test propositions derived from Gestalt theory (Avant, 1965; Metzger, 1930).

Like the Maimonides dream studies, the psi ganzfeld procedure has most often been used to test for telepathic communication between a sender and a receiver. The receiver is placed in a reclining chair in an acoustically isolated room. Translucent ping-pong ball halves are taped over the eyes, and headphones are placed over the ears; a red floodlight directed toward the eyes produces an undifferentiated visual field, and white noise played through the headphones produces an analogous auditory field. It is this homogeneous perceptual environment that is called the Ganzfeld ("total field"). To reduce internal somatic "noise," the receiver typically also undergoes a series of progressive relaxation exercises at the beginning of the ganzfeld period.

The sender is sequestered in a separate acoustically isolated room, and a visual stimulus (art print, photograph, or brief videotaped sequence) is randomly selected from a large pool of such stimuli to serve as the target for the session. While the sender concentrates on the target, the receiver provides a continuous verbal report of his or her ongoing imagery and mentation, usually for about 30 minutes. At the completion of the ganzfeld period, the receiver is presented with several stimuli (usually four) and, without knowing which stimulus was the target, is asked to rate the degree to which each matches the imagery and mentation experienced during the ganzfeld period. If the receiver assigns the highest rating to the target stimulus, it is scored as a "hit." Thus, if the experiment employs judging pools containing four stimuli (the target and three "decoys" or control stimuli), then the hit rate expected by chance is .25. The ratings can also be analyzed in other ways; for example, they can be converted to ranks or standardized scores within each set and analyzed parametrically across sessions. The similarity ratings can also be made by outside judges using transcripts of the receiver's mentation report.

The Debate Over the Ganzfeld Database

In 1985 and 1986, the Journal of Parapsychology devoted two entire issues to a critical examination of the ganzfeld database, which at the time contained 42 studies, including five of Chuck's. The 1985 issue comprised a meta-analysis and critique of the studies by Ray Hyman (1985)--a cognitive psychologist and skeptical critic of parapsychological research--and a competing meta-analysis and rejoinder by Chuck (Honorton, 1985). The 1986 issue contained four commentaries on the Hyman-Honorton exchange, a joint communique by Hyman and Honorton (1986), and six additional commentaries on the joint communique itself.