By Mark Leary, Ph.D., Duke University
Parapsychology has always captured the fascination of the human mind. While there are many who believe that people possess powers or extrasensory perception (ESP), there are others who do not believe in this idea. One of the best-designed research studies on ESP is the ganzfeld procedure. How reliable are the results of this study though? Read to know more.
The Ganzfeld Procedure
Since J. B. Rhine’s ground-breaking work in ESP, numerous psychologists have researched people’s ability to possess psychic abilities. The ganzfeld procedure is one of the best designed research studies to study ESP. Ganzfeld is a German word meaning ‘total field’. It refers to looking at a uniform and featureless image, like staring out at a featureless snowy landscape or sitting in a perfectly dark room.
In some of the research that were conducted, participants were exposed to a ganzfeld by putting halves of ping-pong balls over their eyes and then bathing the room in a red light so that all they would see is a red glow coming through the ping pong balls. The participants were also asked to wear headphones through which a soft hissing sound was played to cover up any sounds in the lab as the subject relaxed in a soundproof room.
The idea behind using the ganzfeld procedure was that ESP may be so weak that it often gets covered up by all the stimuli coming in through our senses. If that is the reason, cutting a person off from normal sights and sounds may make it easier for ESP to operate, or at least, that was the rationale behind the ganzfeld procedure. Here, the participant’s goal was to try to pick up what was in another person’s mind.
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How is Ganzfeld Procedure Conducted?
There are two participants in this procedure: the sender and the receiver. While the receiver relaxes with ping pong balls over his or her eyes, the sender is shown a randomly chosen picture and is asked to try to mentally send that image to the receiver for 30 minutes. When time is up, the ping pong balls and headphones are removed, and the receiver is shown a set of four pictures, one of which is the picture that the sender was trying to send. The receiver is supposed to pick the picture he or she thinks the sender was viewing—the picture that most closely resembles the thoughts and images that were going through the receiver’s mind during the study.
If the receiver just guesses, he or she has a 1 in 4 chance of picking the picture that the sender was sending. However, many of the ganzfeld studies showed that receivers picked the correct picture significantly more than 25 percent of the time.
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Meta-Analysis of the Ganzfeld Procedure
When researchers want to examine the combined findings of many studies that have investigated the same phenomenon, they turn to a statistical procedure called meta–analysis, which statistically combines the results of many studies to reach a general conclusion.
A research is subject to all types of possible biases and chance findings. However, combining the results of many studies, conducted by different investigators in different laboratories on different samples of people, should show the overall effect. The first meta-analysis of the ganzfeld studies looked at 28 experiments, and in 23 of those 28 experiments, the receivers picked the actual picture being viewed by the sender above the chance rate of 25 percent. In fact, the average hit rate across all 28 studies was 35 percent instead of the chance guessing level of 25 percent, and the statistical probability of participants guessing the right picture 35 percent of the time by chance alone is about one in a billion!
This seemed to be a big issue. However, one ought to consider factors other than psi that might cause such a large effect in a meta-analysis. One thing that could make it seem that participants in the ganzfeld studies selected the right picture at such a high rate is selective reporting.
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The File-Drawer Problem
In all scientific fields, studies that obtain significant results are much more likely to be published in scientific journals than studies that don’t obtain significant effects. There is a possibility that there are many failed and unpublished research locked up in researchers’ inventories, and if those failed researches are used in meta-analysis, one would not be able to find an overall effect. This is known as the file-drawer problem.
Researchers who conduct meta-analyses often request other scientists to send them research that weren’t published to get better results. But it is unsure how many such studies exist. In the case of the meta-analysis of the ganzfeld studies, analyses revealed that there would have to be an additional 423 fugitive studies that did not find significant effects to cancel out the significant effects of the published studies.
However, this idea seems to be too stretched out. Even critics of the ganzfeld research agreed that it’s very unlikely that there are so many unpublished studies. Therefore, it can be assumed that the positive results of the meta-analysis are not due to selective reporting or the file-drawer problem. However, there may be methodological problems with the ganzfeld studies that led participants (receivers) to guess the right picture without psychic ability being involved at all.
Common Questions about the Ganzfeld Procedure
Ganzfeld is a German word meaning ‘total field’. It refers to looking at a uniform and featureless image, like staring out at a featureless snowy landscape or sitting in a perfectly dark room.
The idea behind using the ganzfeld procedure was that ESP may be so weak that it often gets covered up by all the stimuli coming in through our senses. So cutting a person off from normal sights and sounds was expected to make it easier for ESP to operate.
In a ganzfeld study, participants were exposed to a ganzfeld by putting halves of ping-pong balls over their eyes and then bathing the room in a red light so that all they would see is a red glow coming through the ping pong balls. They were also asked to wear headphones through which a soft hissing sound was played to cover up any sounds in the lab as the subject relaxed in a soundproof room.
File-drawer problem refers to the possibility that there are many failed and unpublished research that are locked up in researchers’ inventories, and if those failed researches are used in meta-analysis, one would not be able to find an overall effect.
