Parascience has so far failed to produce a single repeatable finding and, until it does, will continue to be viewed as an incoherent collection of belief systems steeped in fantasy, illusion and error.
Originally appeared in Nature Vol. 320, 13 March 1986, pp. 119-124.
Few fields of inquiry capture the attention of the public as much as the paranormal. Newspapers, books, films and television have all cashed in and promoted it. Yet after millennia of experience and more than a century of controlled investigation, since the founding in 1882 of the Society of Psychical Research, the paranormal remains as controversial as ever. While credence in extrasensory perception (ESP) and precognition is widespread, parapsychology has failed to produce a single repeatable demonstration. In the face of such a dearth of hard evidence, how can such widespread belief in the paranormal be accounted for?
The importance of rigorous analysis of the evidence for parascientific claims cannot be underestimated. The establishment of ESP could conceivably require a paradigm shift (in Kuhn’s sense) of the most fundamental kind and our concepts of mind-brain relationships and consciousness would need radical alteration. Our whole approach to psychology as an empirical science, based as it is on the time-honoured assumption that perception can result only from sensory activity, would be brought into question.
The conventional response of many scientists to the paranormal is to ignore the evidence on a priori grounds, believing it to be of basically poor quality. This attitude is allied to the Humean stance that a lie is more probable than a miracle. Although this scepticism is certainly justified, it could be argued that such a blanket response is counterproductive. First, it is hardly scientific to reject a claim purely because of its a priori improbability. Second, a division is created between aligned groups of committed ‘believers’ and ‘sceptics’ and the resulting adversarial positions inhibit proper discourse and the possibility of an account which satisfies all parties. Third, it leaves the field open for undisciplined exploitation, which is irresponsible; there are many examples of financial loss, suffering and even death resulting from fraudulent paranormal claims (for example, the Jonestown massacre, psychic surgery, the Transcendental Meditation levitation programme, firewalking, scientology and other pseudoscientific cults). For scientists passively to ignore such developments is, to say the least, uncharitable.
The Committee for the Scientific Investigation of Claims of the Paranormal (CSICOP) was established in 1976 with the aim of increasing the quality of scientific investigations into the paranormal by constructive criticism and the exposure of invalid or fraudulent claims. Over this 10- year period, an inordinate amount of fraud, error and incompetence in paranormal investigations has been brought to light1-11. But pseudo-sciences are remarkably stable and tradition-bound; their presence on the edges of science can be expected indefinitely12.
Areas of experimental psychology can shed light on the paranormal, especially the study of consciousness and cognition. Such investigation indicates that the many anomalies of putatively paranormal experience are an inevitable consequence of normal selective and constructive processes in perception, memory and imagery. I summarize here what seem to be the common assumptions on which claims of the paranormal are based.
Paranormal phenomena are negatively defined. A phenomenon is defined as paranormal only if it contravenes some fundamental and well-founded assumption of science. Hence, to establish an effect as paranormal, all possible ‘normal’ explanations must be shown to be invalid. Any paranormal claim thus also remains provisional; a normal explanation, not previously thought of, may be discovered at some future time.
Mysteriousness per se is a necessary but insufficient condition for adjudging an event as paranormal. There will always be limits to knowledge, so that new phenomena that initially appear anomalous will be given a natural explanation following systematically controlled observations. Bona fide paranormal effects, on the other hand, are supposed to contravene established assumptions as though from another order of existence and not simply for lack of explanation. ‘Contranorrnal’ would be a more precise technical term.
Examples of effects which until recently were claimed to be paranormal but which can now be explained from within orthodox science include:
- Kirlian photography, the photographic recording of coronal discharges around living or non-living objects produced by high-voltage, (20-100 kV), high-frequency (75 kHz-3 MHz) electrical fields13 14 Variations in the images of the corona can be explained in terms of normal physical factors such as moisture, pressure or distance, all of which influence circuit resistance.
- Fire-walking, if conducted briskly on hot materials of low thermal capacity and poor thermal conductivity, does not produce burns15 16. The Leidenfrost effect created by an insulating layer of water or sweat may also reduce energy transfer to the surface of the body.
- Dowsing is based on sensory cues, expectancy effects and probability. Controlled trials fail to produce above-chance results8,17-19.
- Psychic surgery, thought photography and metal bending all involve sleight-of-hand and can be duplicated by skilled magicians 8,20-22.The first differs from the others in respect of the associated false hopes and financial loss, but all three are fraudulent.
- ‘Gellerized’ watches2l,22, thought to be broken, are purportedly repaired by illusionist Uri Geller by ‘psychic concentration’. In about 50% of cases, simply holding the watch in a clenched fist and shaking it provides a sufficient stimulus to free the mechanism23.
- Astrology, graphology, tea-leaf and tarot card readings, the I Ching and other forms of divination are all types of ‘cold reading’ or ‘sleight-of-mouth’ 24. They depend upon ambiguous, wish-fulfilling and general advice, the use of prior or presented information and cues obtained by verbal ‘fishing’. A strong feeling of personal validation often accompanies such readings. Various forms of ‘mediumship’ and ‘psychometry’ as practised by D. Collins and D. Stokes are also examples of cold reading.
In some cases, field observations can be checked under laboratory conditions and the sensori-motor features of the original performance reproduced using a delayed control group of non-psychic subjects; for example, Geller’s watch-starting procedure and ability to draw the contents of sealed and apparently opaque envelopes were matched by that of non-psychic controls” (Fig. 1). Clearly, the tendency to judge a mysterious event as paranormal in the absence of controlled observations can be quite misleading.
The most dramatic evidence for the paranormal has been based on either fraud or methodological error. Apparent frauds that have been uncovered include University of London mathematician S. G. Soal’s manipulation of his recording sheets25-27, University of Utrecht Professor Tanhaeff’s evidence on Croiset, the Dutch ‘psychic’ detective28, and the description by C. Castaneda (University of California at Los Angeles) of the paranormal teachings of Don Juan29. C. E. M. Hansel3 has provided a valuable review of the history of trickery, fraud and error in parapsychology. However, outright fraud is not the only vehicle in which the paranormal cause can travel, and it is a serious mistake to assume it is a necessary part of any paranormal investigation.
There are no theories to account for paranormal effects or their properties.There are some undesirable implications of this aspect. First, investigators are unable to conduct properly controlled experiments on the properties of psi phenomena because they have no idea what the relevant variables are. In particular, there is no procedure by which psi can be deliberately switched on or off, and so there is no possibility of examining the effects of psi on other variables. All that can be done is to establish whether a given performance in some particular set of circumstances differs from a baseline; if so, psi is assumed to be the cause.
Oddly, neither the subject nor the experimenter can state which of the successful trials in a psi experiment result purely from chance guessing and which are generated by psi, so that there is no basis for distinguishing between a high score in a psi experiment and a lucky run in a game of chance. Also, the persistence of psi investigators in the face of variable but mainly negative results could have a similar motivational basis to that of addicted gamblers; both show high resistance to extinction following variable ratio schedules of reinforcement 30.
A more fundamental problem with the paranormal’s atheoretical status is that of untestability. Failure to observe a particular effect can be readily attributed to a host of ad hoc, hypothetical factors. Vivid imagination is no substitute for testability, however, and if ad hoc hypotheses are not independently testable, nor is the original claim31.
It has been stated that the participants in any experiment may unconsciously determine the results according to whether they themselves believe in psi, the so-called ‘sheep-goat’ effect32. Hence, psi can be held to be present whatever the results, unless the belief of the investigators is itself independently controlled.
In an extreme version of the ‘sheep-goat’ hypothesis, some investigators have even proposed that the participants in an experiment need not be restricted to the individuals in the laboratory but could also include all of the readers of the journal which subsequently publishes the results33! In this case the proportion of sceptics and believers among the eventual readership would determine the experimental outcome through backward causality. Similar in kind is the ‘shyness effect’, the tendency of metal not to bend psychically while it is being observed34.
Evidence of the Paranormal Incompatible with Materialism
Investigators throughout history have been convinced that evidence of the paranormal proves that materialism must be wrong. This was assumed by the Society of Psychical Research, one of whose early presidents, Sir William Barrett, spoke of parapsychology ‘as the most valuable handmaid to religion’35. J. B. Rhine36, the founder of the Parapsychology Association and C. Tart37, a former president, have both reiterated the religio-spiritual motive for pursuing psi research.
An immaterial ‘soul’ has passed out of the formal language of parapsychology, but anti-materialism is still the backbone of the underlying philosophy. A. Flew has described the profound logical difficulties with an immaterial, immortal entity which somehow discriminates its own mental experiences from that of all others38. But even putting that issue to one side, it is curious how seldom the anti-materialist assumption has been properly explained. D. E. Cooper indicated one way in which the anti-materialist argument can be constructed as a reductio ad absurdum, but he found this to be incoherent39. In fact, it seems doubtful that materialism and ESP would be incompatible, should real evidence of ESP ever be found. As M. Scriven has pointed out, materialism can always be enlarged to absorb newly substantiated phenomena, “since the very act of substantiation demonstrates that the phenomena are indeed part of the material world, and hence that a current version of materialism must embrace them40.”
The failure of paranormal investigators to produce a single repeatable effect despite 100 years of published research is a serious matter. The hoped-for results have been described in thousands of reports, but not one can be repeated in a properly controlled replication. Yet in addition to the huge literature of unrepeatable findings, there is an inestimable number of unpublished and presumably negative results.
The most systematically investigated area is undoubtedly parapsychology. The field is professionally organized, with its own associations of accredited members and journals. Since 1969 the Parapsychological Association has been an affiliated division of the American Association for the Advancement of Science. On the surface, the research sophistication of many parapsychologists seems to be as high as that of other professional researchers. The University of Edinburgh now has its own Koestler Chair of Parapsychology. Yet parapsychology is unique in that it remains permanently in search of a reliable finding. In spite of the long history of error, fraud and negative results, the practitioners remain confident that a positive result will soon be obtained. While many abortive leads have been reported in its major publications (for example, Advances in Parapsychological Research, Handbook of Parapsychology 41, Journal of Parapsychology), there is no paradigmatic experiment in the Kuhnian sense, and every new investigator must start afresh, as though he or she is the first worker in the field.
Leading parapsychologists acknowledge the unrepeatability and admit that no single experiment has been free of error. J. Beloff42 and R. Morris43 have concluded that the best case for psi rests on collections of experiments which, although individually flawed, reveal the undeniable presence of psi. But badly con-trolled experiments prove nothing, no matter how large the collection.
If any genuinely repeatable effect is ever discovered, then existing science would be modified to accommodate the new finding, which would then become an integral part of materialist science. The continued existence of ‘parascience’ as a separate field depends upon the investigators’ creativity in searching for new, unexplained anomalies of a singularly unrepeatable kind.
How close are we to a repeatable paranormal finding? Examination of the literature suggests, not very. In systematic reviews of parapsychological experiments, C. Akers44and R. Hyman45 have independently come to the same conclusion: that the research methods and evidence are too weak to establish the existence of a paranormal phenomenon.
Akers reviewed a representative sample of 54 published experiments which used unselected subjects and reported significant results. The sample included 11 experiments using the ganzfeld technique (in which the eyes and ears receive unpatterned sensory inputs), 12 hypnosis experiments, 12 studies of personality correlates, 10 studies of attitude correlates, 5 relaxation experiments and 4 meditation experiments. Akers identified seven sources of methodological error and the majority of experiments included one or more errors (see Table 1).
Hyman’s analysis included 42 ganzfeld experiments reported during 1974-81. Twenty-three (55%) claimed significant evidence of psi on at least one performance measure. Giving consideration to what ca n he counted as an independent study, Hyman concluded that the true success rate was at most 31 %. Moreover, many studies had conducted multiple statistical testing by analysing more than one performance measure and Hyman suggested that a more realistic significance level would have been as high as 0.25 instead of the nominal 0.05 level. Hence, the effective significance level and percen-tage of significant results are approximately equal.
Hyman’s tally of procedural flaws is shown in Table I. None of his sample was judged to be free of flaws, while Akers adjudged only eight of his sample to be flawless, but stated that none could be considered ideal.
The much-publicized experiments on remote viewing by Puthoff and Targ46 are also invalid because of the many sensory cues47 non-randomization47 and inappropriate statistics48. Tart organized a reanalysis of this research and claimed to have removed all of the sensory cues and obtained the same highly significant results49. However, he did not in fact remove all of the cues as he had stated. Attempted replications of the remote-viewing research are either flawed or, in the case of well-controlled studies, show no evidence of ESP50.
This review leads to only one conclusion: there is no scientific evidence of ESP. Yet millions of people throughout the world believe in the reality of ESP and other paranormal phenomena. How can these two facts be reconciled? Is science mistaken, or are folk beliefs manufactured from error and illusion?
- Kurtz, P. Skeptical Inquirer 3, 14-32 (1978).
- Diaconis. P. Science 201, 131-136 (1978).
- Hansel. C. E. M. ESP and Parapsychology: A Critical Reevaluation(Prometheus, Buffalo. 1980).
- Marks. D. & Kammann, R. The Psychology of the Psychic (Prometheus, Buffalo, 1980).
- Alcock. J. E. Parapsychology: Science of Magic? (Pergamon, Oxford, 1981).
- Frazier. K. (ed.). Paranormal Borderlands of Science(Prometheus, Buffalo. 1981).
- Gardner, M. Science Good Bad and Bogus (Prometheus, Buffalo. 1981).
- Randi. J. Flim-Flam! Psychics, ESP. Unicorns. and Other Delusions(Prometheus. Buffalo. 1982).
- Kurtz. P. Skeptical Inquirer 8, 239-246 (1984).
- Frazier. K. (ed.) Science Confronts the Paranormal (Prometheus. Buffalo, 1985).
- Kurtz, P. (ed.) A Skeptics Handbook of Parapsychology (Prometheus. Buffalo, 1985).
- Bunge, M. Skeptical Inquirer 9, 36-46 (1984).
- Tiller, W. A. New Scient. 62, 160-163 (1974).
- Pehek, J.O.,Kyler, H.J. & Faust. D. L. Science 194, 263-270 (1976).
- Houdini Miracle Mongers and Their Methods (Prometheus, Buffalo, 1981).
- Leikind, B. J. & McCarthy, W. J. Skeptical Inquirer 10, 23-34 (1985).
- Vogt, E. H. & Hyman, R. Waterwitching USA 2nd edn (Chicago University Press. 1979).
- Randi, J Skeptical Inquirer 8, 329-333 (1984).
- Martin. M. Skeptical Inquirer 8, 138-140 (1983).
- Randi, J. The Magic of Uri Geller (Ballantine, New York, 1975).
- Fuller, U. Confessions of a Psychic (Karl Fulves, Box 433, Teaneck, New Jersey, 1975).
- Fuller, U. Further Confessions of a Psychic (Karl Fulves, New Jersey, 1980),
- Marks, D. &Kammann. R. Zetetic 1(2),9-17 (1977).
- Hyman, R. Zeteric 1(2). 18-37 (1977).
- Soal, S. G. & Goldney, K. M. Proc.. Soc. psychical Res. 47, 21-150 (1943).
- Scott, C. & Haskell, P. Nature 245, 52-54 (1974).
- Marwick, B. Proc.. Soc. psychical Res.56, 250-281 (1978).
- Hoebens, P. H. Skeptical Inquirer 6, 32-40 (1981).
- De Mille, R. Castandeda’s Journey2nd ed (Capra. Santa Barbara, 1978).
- Skinner, B. F. Science and Human Behavior (Macmillan, New York, 1953),
- Bunge, M. Method, Model and Matter (Reidel, Dordrecht, 1973).
- Schmeidler, G. R. & McConnell, R. A. ESP and Personality Patterns (Yale University Press, 1958).
- Collins, H. M. & Pinch. T. J. Frames of Meaning: The Social Construction of Extraordinary Science (Routledge & Kegan Paul, London, 1982).
- Taylor, J. Superminds: An Inquiry into the Paranormal (Macmillan, London, 1975).
- Barratt, W. Proc.. Soc. psychical Res34, 275–297 (1924)..
- Rhine, J. B. The Reach of Mind, 209-214 (Sloane. New York, 1947).
- Tart, C. T. Psi: Scientific Studies of the Psychic Realm, vii-viii (Dutton. New York, 1977).
- Flew. A. in Science, Pseudo-Science and Society (edsHanen, M. P., Osler, M. J. & Weyant, R. G.) 55-75 (Wilfrid Laurier University Press, Waterloo, 1980).
- Cooper. D. E. in Philosophy and Psychical Research (ed. Thakur, S. C.) 59-80 (Allen & Unwin. London, 1976).
- Scriven, M. in Philosophy and Psychical Research (ed. Thakur, S. C.) 181-194 (Allen & Unwin. London. 1976).
- Wolman, B. J. (ed.) Handbook of Parapsychology (Van Nostrand. New York. 1977).
- Beloff, J. Zetetic Scholar 6, 90-94 (1980).
- Morris. R. L. J. Am. Soc. psychical Res. 74, 425-443 (1980).
- Akers, C. in Advances in Parapsychological Research Vol. 4 (ed. Krippner, S.) 112-164 (McFarland, Jefferson, North Carolina, 1984).
- Hyman, R. J. Parapsychol. 49, 3-49 (1985).
- Targ, R. & Puthoff, H. E. Nature 252, 602-607 (1974).
- Marks, D: F. & Kammann, R. Nature 274. 680-681 (1978).
- Hyman, R. Skeptical Inquirer 9, 125~ 145 (1984-5).
- Tart, C. T.. Puthoff, H. E. & Targ, R. Nature 284. 191 (1980).
- Marks, D. F. Skeptical Inquirer 6, 18-29 (1982).
- O’ Keefe, D. Stolen Lightning (Robertson, Oxford, 1982).
- Wilson, S. C. & Barber, T. X. in Imagery: Current Theory, Research and Application (ed. Sheikh, A. A.) 340-387 (Wiley. New York, 1983).
- Marks, D. & McKellar, P. J. mental imagery 6, 1-124 (1982).
- Gurney, E. &Myers, F. W. H. Proc. Soc. psychical Res. 5, 403-485 (1889).
- Sidgwick, H. Proc. Soc. psychical Res. 10, 25-422 (1894).
- Finucane, R. C. Appearances of the Dead (Prometheus, Buffalo. 1985).
- Zusne, L. & Jones, W. H. Anomalistic Psychology (Erlbaum, Hillsdale, New Jersey, 1982).
- Edwards, W. in Formal Representation of Human Judgement (ed. Kleinmuntz, B.) 17-52 (Wiley, New York, 1968).
- Nisbett, R. & Ross, L. Human Inference: Strategies and Shortcomings of Social Judgment (Prentice-Hall, Englewood Clills. 1980).
- Hoebens, P. H. Skeptical Inquirer 7, 38-45 (1982).
- Klass, P. J. Zetetic 2, 57-61 (1977).
- Koestler, A. The Roots of Coincidence (Hutchinson, London, 1972).
- Rhine, L E. J. Parapsychol. 15, 164-190 (1951).
- Tart, C. T. Learning to Use Extrasensory Perception (University of Chicago Press, 1976).
- Tart, C. T., Palmer, J. & Redington, D. J. J. Am. Soc. psychical Res. 73, 151-165 (1978).
- Dixon, N. F. Preconscious Processing (Wiley, Chichester, 1981 ).
- Franselle. F. & Bannister. D. A Manual for Repertory Grid Technique (Academic, London, 1977).
- Windholz, G. & Diamant. L. Bull. psycnon. Sci. 3, 125-126 (1974).