Approved For Release 2000/08/10 : CIA-RDP96-00792R00010013Q003-0 , PSI PHENOMENA Daryl J. Bem Cornell University Experimental Evidence Debate over the Evidence Replication Problem Inadequate Controls File-Drawer Problem Anecdotal Evidence Skepticism about Psi Extraordinary Claims Skepticism of Psychologists References Prepared for inclusion in Atkinson, R, L, Atkinson, R. C., Smith, E. E., & Bem, D. J. (1990). Introduction to Psychology (10th Ed). San Diego: Harcourt Brace Jovanovich. Iam grateful to Charles Honorton, Robert Rosenthal, and Marcello Truzzi for comments on earlier drafts. Still subject to editing. Please do not quote without permission. Approved For Release 2000/08/10 : CIA-RDP96-00792R000100130003-0
pproved For Release 2000/08/10 : CIA-RDP96-00792R000100130003- a pe *henomena PSI PHENOMENA Is it possible for us to acquire information about the world in ways that do not involve stimulation of the known sense organs or to influence physical events by purely mental means? These questions are the source of controversy over the existence of psi, processes of information and/or energy exchange not currently explicable in terms of known science. The phenomena of psi are the subject matter of parapsychology (“beside psychology”) and include the following: | 1. Extrasensory Perception (ESP). Response to external stimuli without sensory contact. a. Telepathy. Response to the mental state of another person without the mediation of any known channel of sensory communication (for example, identifying a playing card merely being thought of by another person) b. Clairvoyance. Response to objects or events that do not provide a stimulus to any known sense (for example, identifying a concealed playing card whose identity is unknown to anyone) | c. Precognition. Response to a future event that could not be anticipated through any known inferential process (for example, predicting which digit a random number generator will generate on the next trial) 2. Psychokinesis (PK). Mental influence over physical events without the mediation of any known physical force (for example, influencing which digit a random number generator will generate on the next trial) Experimental Evidence Most parapsychologists consider themselves to be scientists applying the usual rules of scientific inquiry to admittedly unusual phenomena. Yet the phenomena of psi are so extraordinary and so similar to what are widely regarded as superstitions that some scientists Approved For Release 2000/08/10 : CIA-RDP96-00792R000100130003-0
Approved For Release 2000/08/10 : CIA-RDP96-00792R000100130003-0 Psi Phenomena 2 declare psi to be an impossibility and reject the legitimacy of parapsychological inquiry. Such a priori judgments are out of place in science; the real question is whether the empirical evidence is acceptable by scientific standards. Many psychologists who are not yet convinced that psi has been demonstrated are nevertheless open to the possibility that new evidence might emerge that would be more compelling. For their part, many parapsychologists believe that several recent experimental procedures either provide that evidence already or hold the potential for doing so. We shall examine one of the most promising of these, the ganzfeld procedure. The ganzfeld procedure tests for telepathic communication between a subject acting as the “receiver” and another person who serves as the “sender.” The subject is sequestered in an acoustically-isolated room and placed into a mild form of perceptual isolation: translucent ping-pong ball halves are taped over the eyes and headphones are placed over the ears; diffuse red light illuminates the room, and white noise is played through the headphones. (White noise is arandom mixture of sound frequencies similar to the hiss made by a radio tuned between stations.) This homogeneous visual and auditory environment is called the Ganzfeld, a German word meaning “total field.” The sender is sequestered in a separate acoustically-isolated room, and a visual stimulus (picture, slide, or brief videotaped sequence) is randomly selected from a large pool of similar stimuli to serve as the “target” for the session. While the sender concentrates on the target, the subject attempts to describe it by providing a continuous verbal report of his or her ongoing imagery and free associations. Upon completion of the session, the subject is presented with four stimuli—one of which is the target—and asked to rate the degree to which each matches the imagery and associations experienced during the ganzfeld period. A “direct hit” is scored if he or she assigns the highest rating to the target. (In some studies, individuals unconnected with the experiment also attempt to match a transcript of the subject’s verbal report to the target.) More than 50 ganzfeld experiments have been conducted since the procedure was first introduced in 1974. An overall analysis of 28 studies reported through 1981—comprising 835 Approved For Release 2000/08/10 : CIA-RDP96-00792R000100130003-0
Approved For Release 2000/08/10 : CIA-RDP96-00792R000100130003-0 Psi Phenomena 3 ganzfeld sessions conducted in 10 different laboratories—reveals that subjects selected the target 38% of the time on the average. (Because there are 4 alternatives, we would expect a success rate of 25% if only chance were operating.) Statistically this result is highly significant: the probability that it could have arisen by chance is less than one in a billion (Honorton, 1985). Debate over the Evidence In 1985 and 1986, the Journal of Parapsychology published an extended examination of the ganzfeld studies, focusing on a debate between Ray Hyman, a cognitive psychologist ~ and critic of parapsychology, and Charles Honorton, a parapsychologist and major contributor to the ganzfeld database. They agree on the basic quantitative results but disagree on points of interpretation (Hyman, 1985; Hyman & Honorton, 1986; Honorton, 1985). We shall use their debate as a vehicle for examining the major issues involved in evaluating all claims of psi. Replication Problem In science generally, a phenomenon is not considered established until it has been observed repeatedly by several researchers. Accordingly, the most serious criticism of parapsychology is that it has failed to produce a single demonstration of psi that can be reliably replicated (successfully reproduced) by other investigators. Even the same investigator testing the same individuals over time may obtain significant results on one occasion but not on another. The ganzfeld procedure is no exception; fewer than half (43%) of the 28 studies analyzed in the debate yielded statistically significant results. The parapsychologists’ most effective response to this criticism actually comes from within psychology itself. Many statisticians and psychologists are dissatisfied with psychology’s focus on the significance level as the sole measure of a study’s success. As an alternative, they are increasingly adopting the technique of meta-analysis, a technique that treats the accumulated studies of a particular phenomenon as a single grand experiment and each study as a single observation. Thus any study that obtains results in the positive direction— even though it may not be statistically significant itself—contributes to the overall strength and Approved For Release 2000/08/10 : CIA-RDP96-00792R000100130003-0
Ppprovee-for Release 2000/08/10 : CIA-RDP96-00792R000100130003-0 4 reliability of the phenomenon rather than simply being dismissed as a failure to replicate (Glass, McGaw, & Smith, 1981; Rosenthal, 1984). From this perspective, the ganzfeld studies provide impressive replicability: 23 (82%) of the 28 studies obtain positive results (more direct hits than chance would predict), a result whose probability of occurring by chance is less than 1 in a thousand. The conventional criterion of replication further requires that any competent investigator be able to reproduce the claimed phenomenon, not just one or two gifted experimenters. This is often a difficult criterion to achieve in new areas of investigation because a number of unsuspected variables might affect the outcome. In psychological experiments, the experimenter is often an important social stimulus for the subject and hence a poorly controlled source of variability. Even in such an established area as classical conditioning, investigators at one university were obtaining positive results 94% of the time while other investigators could do so only 62% of the time (Rosenthal, 1966; Spence, 1964). Nor is psychology alone here. Similar replication difficulties have been reported in medical studies of placebo efficacy (Moerman, 1981) and in the physical science area of laser technology (Collins, 1974). This problem may be even more acute in parapsychology because psi effects may legitimately depend upon the motivational atmosphere established by the experimenter. Some parapsychologists further believe that the experimenter’s own psi abilities and/or attitudes can affect the results. Despite these potential difficulties, the replicability of the ganzfeld effect does not appear to rest on the success of one or two investigators. Six of the 10 investigative teams contributing to the 28 examined studies obtained statistically significant results; and, even if all the studies from the two most successful laboratories are discarded from the analysis (half of the studies), the results remain significant (Palmer, Honorton, & Utts, 1988). The power of a particular experiment to replicate an effect also depends upon how strong the effect is and how many observations are made. If an effect is weak, an experiment Approved For Release 2000/08/10 : CIA-RDP96-00792R000100130003-0
approved For Release 2000/08/10 : CIA-RDP96-00792R000100130003-0 s] Phenomena 5 with too few subjects, sessions, or observations will fail to detect it at a statistically significant level-—even though the effect actually exists. | This is strikingly illustrated by a recent medical experiment designed to determine whether aspirin can prevent heart attacks. The study was discontinued in 1987 because it was already clear the answer was yes. After six years, the aspirin group had already suffered 45% fewer heart attacks than a control group which received only placebo medication, a result that would occur by chance less than one time out of a million (The Steering Committee of the Physicians’ Health Study Research Group, 1988). With such impressive results, it was considered unethical to keep the control group on placebo medication. The study was widely publicized as a major medical breakthrough. The pertinent point here is that the study included over 22,000 subjects. If it were to be repeated with 3,000 subjects, a significant aspirin effect would be unlikely to emerge; the experiment would fail to replicate. Despite its undisputed reality and its practical importance, the aspirin effect is actually quite weak. Now reconsider the ganzfeld effect. If the effect actually exists and has a true direct-hit rate of 38%, then statistically we should expect ganzfeld studies with 30 sessions (the average for the 28 studies) to obtain a significant psi effect only about one-third of the time (Utts, 1986). The ganzfeld effect is about 4 times stronger than the aspirin effect. In short, it is unrealistic to demand that any “real” effect be replicable at any time by any competent investigator. The replication issue is more complex than that, and meta-analysis is proving to be a valuable tool for dealing empirically with some of those complexities. Inadequate Controls The second major criticism of parapsychology is that many, if not most, of the experiments have inadequate controls and safeguards. Flawed procedures that could permit a subject to obtain the communicated information in normal sensory fashion either inadvertently or through deliberate cheating are particularly fatal. This is called the problem of “sensory leakage.” Inadequate procedures for randomizing (randomly selecting) target stimuli are another common problem. Approved For Release 2000/08/10 : CIA-RDP96-00792R000100130003-0