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European Journal of Parapsychology, 1984, 5, 245-260

 

On the Assessment of Evidence of Psi

 

Nils Wiklund

Karolinska Institute, Stockholm

 

 

      Leading parapsychologists have made selections of important parapsychological experiments.  The resulting list of experiments can be used for the assessment of the evidence for psi.  This approach can yield both a "Yes" and a "No" to the question whether psi exists or not (in contrast to other approaches used by parapsychologists).  It is not an easy task to assess the strength of the present-day experimental evidence for the existence of psi phenomena (i.e. telepathy, clairvoyance, precognition, and psychokinesis).  Some scientists, notably parapsychologists, seem to consider the evidence to be fairly strong; others are not at all impressed.  The primary question in parapsychological research is whether psi phenomena exist or not.  If the answer is yes, this can be established either by a repeatable experiment or by individual experiments that are so well controlled that no other explanation is found.

     If the answer is no, neither method can be very efficient in procuring an answer.  If psi does not exist a repeatable experiment that demonstrates psi cannot be found, and individual experiments containing no artifacts will necessarily yield chance results.  Chance results, however, do not immediately prove the non-existence of psi, and so these two approaches will not yield an answer to the existential question in case psi does not exist.

       The question of the existence of psi is sometimes neglected by parapsychologists.  The majority of those who carry out experiments in parapsychology seem to work under the tacit assumption that paranormal phenomena exist (cf.  Schmeidler, 1971; Beloff, 1973). And yet very few systematic studies have been made to assess the strength of evidence for psi.  More important, the conditions under parapsychologists would be prepared to abandon the hypothesis that psi exists have not as yet been defined.  This means that the assumption that psi exists has a certain similarity with an unfalsifiable assumption.

       To take the existence of psi for granted is associated with various types of risks.  One is that scientists in other fields will continue to ignore parapsychology (Pratt, 1979, p. 24) and that “We shall very quickly degenerate into an insignificant clique of tiresome pseudoscientists" (Beloff, 1973, p 190).  Another closely related risk is that slack experimental procedures may be re-introduced into parapsychological research.  One aspect of this is that parapsychologists may develop certain blindness to alternative explanations to the unidentified experimental effects (interpreted as psi) often found in parapsychological research.  From a methodological point of view it may actually be advantageous to use the assumption that psi does not exist, since this will keep the researcher alert to the various artifacts that may be involved in a particular experiment.  Perhaps a term that does not imply an interpretation would be helpful in this respect.  ESP, both in the sense of ´Extra-Sensory Perception' and in the sense of 'Error Some Place' (Honorton, 1975) implies a rather specific interpretation.  A descriptive term like  'Unidentified Experimental Effects' (UEE) would be more neutral.

      One method to make an assessment of the evidence for psi is to select a number of important experiments and to expose these to a thorough scrutiny.  This method has the potential of yielding both a "Yes" and a "No" to the existential question (in contrast to the methods mentioned above).  If the true answer is "No", it is likely that artifacts will be found.  If the true answer is “Yes”, artifacts will not necessarily be found.

       One necessary prerequisite for this method is to decide which experiments are to be considered as important.  It is quite easy to reveal faults in the reports of parapsychological experiments, but in the absence of a decision as to which experiments are important the only conclusion is that each faulted experiment does not carry any weight for the existence of psi, but then there are an endless number of other studies ... This is similar to the mystical description of God's nature in negative terms "neti, neti - not this, not this". Without a decision as to which experiments are important the dialogue with scientific colleagues in other fields would come to a standstill, but parapsychologists traditionally take a certain pride in welcoming such dialogues.  It is now more than a century since the Society for Psychical Research was founded in 1882, and from this time onwards parapsychologists have been able to keep this dialogue alive and to achieve certain respectability.  One essential aspect of this dialogue has been the presentation of lists of important experiments, e.g. by Rhine et al. (1940).  During a period these experiments were even considered to be crucial for the assessment of the existence of psi.  As long as no flaws had been revealed the weight of the evidence was rather heavy.  Later, artifacts, or the possibility of artifacts, have been demonstrated in some of these experiments, and now the weight of the evidence, of course, appears much lighter.  During the same time new important experiments have been conducted, together with many less important ones, and it is now necessary to make renewed decisions as to which experiments are at present to be considered as particularly evidential.

      The purpose of the present study is to procure such a list of important experiments.  I have asked a number of leading parapsychologists (former presidents of the Parapsychological Association) to make individual selections.  Most of them have fulfilled my request, and this shows that parapsychologists' interest in communication with scientists in other fields is still as strong as it has been from the start.  This list will be helpful for those wishing to make an assessment of the evidence for psi.

 

Participants

 

      Presidents of the Parapsychological Association during the period 1968 to 1978 were contacted for the study.  In accordance with a suggestion from one of the ex presidents, J.G. Pratt was also contacted.  It was reasoned that, even if Dr. Pratt did not happen to be president of the P.A during this period, he was without doubt one of the most important researchers in parapsychology.  Since some of his experimental reports have been particularly scrutinised by those wishing to assess the strength of the evidence for psi (Hansel, 1980; Stevenson, 1967), Dr. Pratt's selection of important experiments may even be of special interest.

      In a letter to the presidents I explained the purpose and the study and how they were supposed to make their selections. Here follows the central parts of the letter:

 

"What I would like you to do is to specify which experiments (or cases) in your opinion constitute good, important studies substantially contributing to the evidence for the existence of psi. The most important thing is that the experiments are methodologically sound.  You must not be aware of any ´artifacts´. Otherwise, I do not impose any limitation on your choices. You can mention any number of experiments, but your choices should be guided by the criterion that if artifacts are discovered in a particular experiment this would noticeably diminish the support for the existence of psi.... If you select  a series of experiments because they seem to yield hope for a repeatable experiment please indicate in particular that this is the reason for your choice and also indicate which of these experiments in  themselves furnish good evidence for psi irrespective of whether the experiment will turn out to be repeatable or not (again with the guiding principle that the evidence for psi would noticeably diminish if artifacts were discovered)."

 

     The first letter to the former presidents of the P.A. was sent in 1979, and by 1981 I had received at least some kind of answer from ten of the twelve persons that I had contacted.  A list of the participants is given below.  The year of their presidentship is given in parentheses together with an abbreviation of their names.

    Specific selections of parapsychological studies were made by the following: Ian Stevenson (I.S., 1968), Hans Bender (H.B., 1969), John Beloff (J.B., 1972), Robert L. Morris (R.L.M., 1974), Martin Johnson (M.J., 1976), K. Ramakrishna Rao (K.R.R., 1978), and J.G. Pratt (J.G.P.).1

     Others answered my request but did not make specific selections. Charles T. Tart (presidential period: 1977) wrote: “Generally speaking I would support the choices of other P.A. presidents as long as the reports were published in P.A. affiliated journals, but I would reserve the right to reject a specific experiments.”  Gertrude R. Schmeidler (presidential period: 1971) explained in detail her reasons for not making a specific selection of parapsychological experiments; her opinion is discussed below.  Robert L. Van de Castle (presidential period: 1970) wrote that he did not have the time to make the selection I wanted.  Only two of the former P.A. presidents did not even return a card, on which I had asked them to state whether they intended to participate in the study or not (Rex G. Stanford and Charles Honorton - presidential periods: 1973 and 1975 respectively).  It is improbable that none of my letters reached them, and I can only surmise that they consider their opinion about making specific selections of experiments to be sufficiently well known from the parapsychological literature (and that it is a negative one).

 

Results

     

     Eight studies (or groups of studies) were chosen by at least two of the P.A. presidents and they are listed here, starting with those studies that were mentioned most frequently.  After each study is mentioned how many times it was chosen and by who.  Twenty five studies were chosen by only one of the P.A. presidents and these will not be further discussed here.

 

(1)     Helmut Schmidt's experiments using a binary random number generator.

(Five: J.B., R.L.M., M.J., K.R.R., J.G.P.)

(2)     The Kanthamani & Kelly experiments with the subject Bill Delmore.

(Four: J.B., M.J., K.R.R., J.G.P.)

(3)     The Stepanek experiments.

(Three: J.B., K.R.R., J.G.P.)

(4)     The Ganzfeld studies.

(Three: J.B., M.J., R.L.M.)

(5)     The Brugmans experiment at Groningen

(Two:  I.S., J.B.)

(6)     The Pearce-Pratt experiments.

(Two:  I.S., K.R.R. - not J.G.P.!)

(7)     The Pratt-Woodruff experiments.

(Two:  I.S., J.G.P.)

(8)     The Roll & Klein experiment with the subject Harribance.

(Two: J.B., K.R.R.)

 

      Diana Robinson (1981) used a different approach in order to get a list of important experiments.  She contacted all the members of the Parapsychological Association and asked them to make selections of parapsychological experiments.  It is interesting to compare her results with the choices made by the P.A. presidents. It turns out that her final list of individual experiments or groups of experiments (Robinson, 1981) includes the first seven choices of t presidents, but not the last one. (I interpret her item ´Pratt´s work in general´ to cover the Pratt-Woodruff series.) In addition Robinson's list includes three other groups of experiments: the so-called remote viewing experiments (associated with Targ, Puthoff, Bisaha, and Dunne), Schmeidler's sheep-goat work, and the Maimonides dream work. None of these was chosen by anyone of the P.A. presidents who participated in my study (although the Maimonides dream work was given an 'honorable mention' by one of them, I.S.)

     Since the first seven choices of the P.A. presidents coincide with the choices made by parapsychologists in general, I think we can consider these seven groups of experiments to represent important parapsychological studies.

 

References

 

      An introductory bibliography to the first seven groups of studies selected by the P.A. presidents is presented here.  It is not meant to be complete, but the references will hopefully be a useful starting point for those who want to make an assessment of the studies.

 

 (1) Helmut Schmidt's experiments.

 

Schmidt, H. Precognition of a quantum process. Journal of Parapsychology, 1969, 33, 99-108.

 

Schmidt, H. Clairvoyance tests with a machine. Journal of Parapsychology, 1969, 33 300-306.

 

Schmidt, H . PK tests with a high speed random number generators.  Journal of Parapsychology, 1973, 37, 105-119.

 

(2)  The Kanthamani & Kelly experiments.

 

Kelly, E.F., & Kanthamani, B.K. A subject's efforts towards voluntary control. Journal of Parapsychology., 1972, 36, 185-197.

 

Kanthamani, H. (B.K.), & Kelly, E.F. Card experiments with a special subject.  I. Simple clairvoyance. Journal of Parapsychology, 1974, 38, 16-26.

 

Kanthamani, H. (B.K.), & Kelly, E.F. Awareness of success in an exceptional subject.  Journal of Parapsychology, 1974, 38, 355-383.

 

Kelly, E.F., Kanthamani, H., Child, I.L., & Young, F.W. On the relation between visual and ESP confusion structures in an exceptional subject. Journal of the A.S.P.R., 1975, 69, 1-32.

 

(3) The Stepanek experiments.

 

Pratt, J.G., Stevenson, I., Roll, W.G., Blom, J.G., Meinsma, G.L., Keil, H.H.J. & Jacobson, N. Identification of concealed randomized objects through acquired response habits of stimulus and word association. Nature, 1968, 220, No. 5162, 89-91.

 

Blom, J.G. & Pratt, J.G. A second confirmatory ESP experiment with Pavel Stepanek as a "borrowed" subject. Journal of the A.S.P.R., 1968, 62, 28-45.  See also letter by Pratt in Journal of the A.S.P.R., 1969, 63, 207-209.

 

Pratt, J.G. A decade of research with a selected ESP subject: an overview and reappraisal of the work with Pavel Stepanek. Proceedings of the A.S.P.R., 1973, 30, 1-78.

 

Keil, H.H.J. Pavel Stepanek and the focusing effect. Research Letter of the Parapsychology Laboratory, University of Utrecht, No. 8, Oct 1977.

 

 (4) The Ganzfeld studies.

 

Honorton, C. Psi and internal attention states. In: Wolman, B.B (Ed.), Handbook of Parapsychology, 1977, Part V, Chap. 1.

 

(5) The Brugmans experiments at Groningen.

 

Brugmans, H.J.F.W. 'Une communication sur des experiences telephatiques au laboratoire de psychologie a Groningen faites par M. Heymans, Dr. Weinberg et Dr. H.I.F.W. Brugmans. Le compte rendu officiel du premier congres international de recherches psychique, Copenhagen, 1922, 396-408.

Murphy, G. Challenge of Psychical Research. New York: Harper, 1961, pp. 56-62.

 

Pope, D.H. The Brugmans experiments. Journal of Parapsychology, 1952, 16, 1-3.

 

Schouten, S.A., & Kelly, E.F. On the experiments of Brugmans, Heymans

and Weinberg. European Journal of Parapsychology, 1978, 2, 247-290.

 

 (6) The Pearce-Pratt experiments.

 

Rhine, J.B. & Pratt, J.G. A review of the Pearce-Pratt distance series of ESP tests. Journal of Parapsychology., 1954, 18, 165-177.

 

Hansel, C.E.M. ESP and parapsychology.  A critical re-evaluation. Buffalo, N.Y., Prometheus Books, 1980, Chap. 10.

 

(7) The Pratt-Woodruff experiments.

 

Pratt, J.G. & Woodruff, J.L. Size of stimulus symbols in extrasensory perception. Journal of Parapsychology, 1939, 3, 121-158.

 

Pratt, J.G. New evidence supporting the ESP interpretation of the

Pratt-Woodruff experiment. Journal of Parapsychology, 1976, 40, 217-227

 

Hansel, C.E.M. ESP and parapsychology.  A critical re-evaluation.

Buffalo, N.Y., Prometheus Books, 1980, Chap. 11.

 

Comments

      It is of particular interest that the Pearce-Pratt and the Pratt-Woodruff experiments are still considered to be good evidence for the existence of psi by many parapsychologists. These experiments have been carefully examined by various investigators, and the assessment of these studies is therefore, greatly facilitated.  It is also of principle importance to see if any parapsychological experiment can stand the test of a thorough critical examination.  We have here then two series of experiments that some parapsychologists   consider to have passed the test. J.G. Pratt, who was involved in both, mentioned only one of them though (the Pratt-Woodruff experiments).  Helmut Schmidt's experiments have also been examined by Hansel in the second edition of his book (1980).  However most of the P.A. presidents made their choice of Schmidt's experiments before this edition of the book appeared.

     The Ganzfeld studies seem to have been chosen not primarily because they represent particularly well-designed experiments from a methodological point of view but because they "have a better record for repeatability than any other type of experiment in recent years” (i.e. in parapsychology) (Beloff, 1980, P. 118).

      The importance of a list of experiments like the present one becomes evident when it is compared with the list of studies examined in the third part of Hansel's book (1980) where he attempts to cover the developments in parapsychological research since 1965.  He considers "the use of machines and automated procedures" to be the most important development since 1965, and therefore he devotes a full chapter to the Helmut Schmidt experiments, which are considered to be important also by the P.A. presidents.  Apart from this, Hansel's choices of experiments do not coincide very much with those chosen by the ex-presidents.  He devotes a full chapter to psychical research at SRI, telepathy and dreams, Uri Geller, the remote viewing experiments, and what he calls "the challenge of chance".  None of these studies was selected by even one of the P.A. presidents as important studies.  In one chapter on "The miracle men" he does, however, devote three pages to the Stepanek experiments.  The Kanthamani & Kelly experiments as well as the Ganzfeld studies are not at all examined. Honorton (1981) is undoubtedly correct in his criticism that "Hansel's coverage of the recent research is highly selective and grossly inadequate" (p. 155).  But how could Hansel know which recent studies to examine when parapsychologists nowadays according to my view often are less eager to specify important experiments than they were in earlier decades? When Hansel's choices are compared with those of parapsychologists in general (Robinson, 1981) it is also found that two further chapters in Hansel’s book are devoted to what they consider to be important studies, although these studies are not selected by the P.A. presidents (the remote viewing experiments and the Maimonides dream work).  And one cannot deny that the rest of Hansel's subject areas have received wide publicity in recent years.

 

Discussion

 

     There are basically two types of objections to the idea of making a list of particularly important parapsychological experiments.  The first objection is that evidence should not be derived from individual experiments but from the combination of all experiments, particularly as they support each other in a systematic (or theoretic) way.  This objection is commonly known as the 'fagot' theory.  The second objection is that individual experiments cannot, in principle, yield conclusive evidence; only a repeatable experiment can do this.

       The first objection was explained in a sympathetic way by Gertrude Schmeidler (1979) in a letter to me.  She wrote:

 

"You wanted a list of experiments in parapsychology, or of cases, on which (here I rephrase what you wrote) conviction depends.  But to my mind, conviction grows slowly and becomes strong and complete only when many, many data accumulate to form a pattern ... conviction comes when a new theory or pattern begins to emerge from diverse findings, and when predictions from a theory are supported by the outcome of research - especially of independent research.  It adds up to a network of interrelated findings which begin to form a meaningful pattern.  And this means that a (linear) list of separate experiments, each of which seems good, isn't an adequate answer to your basic question ... Any one experimental series might contain artifact or be due to fraud.  Our own ingenuity may be insufficient to spot the artifact.  But if data obtained by varied procedures support each other, the artifact of one experiment would not appear in others (which change the particular procedures).  If we spotted an artifact, we've mentally discarded that experiment; if we doubt our ability to spot all responsible artifacts, we're reassured by systematic rather than direct replication."

 

     However, to insist on the cumulative evidential value of all parapsychological experiments will hardly convince the skeptic.  Price (1955) firmly rejected the idea that the 'mass' of experiments carries any evidential value.

 

"But the answer that will impress me is an adequate experiment.  Not 1000 experiments with 10 million trials and by 100 separate investigators giving total odds against change (sic!) of 10 to I - but just one good experiment.  And until such a demonstration has been provided, I hope that my fellow-scientists will similarly withhold belief."

 

     Some of the parapsychologists who insist on the cumulative evidence of all experiments seem to suggest that one should not be preoccupied with isolated studies, because, so far, no individual experiment has been found to be without errors.  They suggest that there probably is no impeccable experiment and, even, that there cannot be one.  This opinion, however, rather amounts to saying that there is no strong evidence for psi, and that there cannot be, which comes very close to saying that psi does not exist.

     The second objection to the idea of making a list of important parapsychological experiments is that individual experiments cannot in principle prove the existence of psi.  Only a repeatable experiment has this capacity.  This approach, however, is of little help in assessing the evidence for psi in the absence of a repeatable experiment.  Many leading parapsychologists seem to be of the opinion that there is at present no genuinely repeatable experiment.  Nevertheless they do not draw the conclusion that paranormal phenomena do not exist.  The absence of a repeatable experiment is not interpreted as a "No" to the question whether psi exists.  The search for a repeatable experiment is, therefore, of limited value when trying to make an assessment of the evidence for psi.  This approach can yield an answer to the question whether psi exists only under the condition that psi does really exist (and a genuinely repeatable experiment would, of course, make the existence of psi uncontroversial). (Penetrating studies have also been made of the very concept of repeatability, e.g. by Bauer, 1979, but a discussion of these studies lies outside the purpose of the present paper.)

     Many parapsychologists seem to work under the assumption that psi phenomena exist, and some even seem to take their existence for granted.  If parapsychologists in general have not seriously considered the possibility of the non-existence of psi, I think this would introduce a considerable methodological danger.  There are, in fact,  signs of an apparent methodological crisis in parapsychology.  Those who take the existence of psi for granted tend to become less aware of the 'anomalous' and 'revolutionary' character of psi phenomena, in Kuhn's (1962) sense of the terms.  As a consequence of this there is the risk of increased blindness for artifacts in the experiments.  There is also a tendency to diminish the rigor of the experimental methods.  In the 1950's the so-called two-experimenter design was proposed as a necessary part of a well conducted parapsychological experiment.  Nowadays it is rarely used.  Some parapsychologists stress the notion that no individual experiment can be 'perfect', and take this as an excuse to re-introduce slack experimental procedures.  Nomina sunt odiosa.  These developments represent a real methodological crisis in parapsychology and warnings have been voiced lest parapsychology will develop into a pseudo-science and "pass more and more into the hands of cranks as its present relatively respectable supporters drop away" (Alan Gould, quoted by Nicol, 1980).  It will not be easy to produce infallible and complete antidotes to this crisis.  Much can be learned from J.B. Rhine's attitude to criticism from his scientific colleagues:

 

"Critics both within and without parapsychology examined the first work and found, or thought they found, methodological loopholes in it.  Rhine welcomed all such criticism and transformed them into constructive contributions: with the help of his colleagues he invented or utilized new methods which would make the research fully rigorous." (Schmeidler, 1981, p. 19)

 

     Not only is it necessary to welcome critical examinations from colleagues in other fields, it would also be favourable if parapsychologists took a more determined responsibility for conducting the critical analyses of 'claims of the paranormal', and for disseminating the results of these analyses.  It is an unfortunate development if this task is delegated to groups of researchers independent of the Parapsychological Association.  I am favourably impressed by some leading parapsychologists for their scientific ability and for their immediate perception of weaknesses in experimental reports, for example at the P.A. conventions.  But it is hardly enough to confine these critical analyses to oral discussions at these conventions.  There is a risk that obviously deficient experiments will be considered to be adequate by parapsychologists in general.  This may be an explanation of some of the differences between the selections of important experiments made by leading parapsychologists as compared to the choices by parapsychologists in general (e.g. concerning the remote viewing experiments). Bauer (1979) stressed that parapsychologists traditionally are the most competent critics of parapsychological experiments, and it seems vitally important to keep this tradition alive.

    There is also another development in parapsychology that has been called a crisis.  It is concerned with the weight of the evidence for psi.  Scriven (1961) described the beginning of this 'crisis' which is characterized by a continuous "erosion of the evidence" for psi. (Cf.  Bauer, 1979) This erosion of the evidence has continued since then, and the weight of the evidence for psi now appears less than it was before.  But this development only shows the strength of parapsychology as a science.  It shows that the scientific methods of parapsychology are still functioning healthily.  This so-called crisis, concerned with the diminished weight of the evidence for psi, is therefore no real crisis, but merely a new phase in the development of parapsychology as a science.

    As researchers in this field we are not necessarily supposed to prove the existence of psi.  It is not even more desirable that paranormal phenomena exist than is their non-existence.  Even less is there any merit in belief or disbelief in the phenomena (Beloff, 1973).  We are merely here to investigate whether the phenomena exist or not.  Depending on the answer to this basic question we can then attempt to find explanations.  If the answer is yes (or judged to be yes) it is natural to search for a theory of psi.  If the answer is no (or judged to be no) it will be necessary to find explanations to the unidentified experimental effects (UEE) in numerous parapsychological experiments, which will probably be of interest from a methodological point of view.  It will also be necessary, and perhaps more interesting from a psychological point of view, to find explanations for the frequently reported spontaneous phenomena of a seemingly paranormal nature, that often carry a strong flavour of conviction for the person experiencing the phenomenon.  If these experiences are not psi occurrences, then what are they?

   Due to an unfortunate incident Dr. Beloff's list was seen by Dr. Rao and by Dr. Pratt before they completed their lists in the fall of 1979.  Dr. Rao has informed me that he does not think he was influenced by Beloff's choices, and supported this view with references to his earlier publications.  This issue is not essential however, since the consensus I was looking for anyhow could be expected to depend on marked interdependence between the opinions of the participants, due to their intimate knowledge of the research field.  Later I also contacted the presidents for 1980 and 1981, but both decided not to make a selection of the experiments.  Dr. Child thought that he would be too much influenced by Dr. Beloff's list that he had already seen, and Dr. Palmer argued that the entire parapsychological literature must be considered.

 

References

 

Bauer, E. 'Kritik und Kontroversen der Parapsychologie', In: Die Psychologie des 20.    Jahrhunderts, XV, p 546-559.  Zürich, Kindler Verlag, 1979.

Beloff.  J. 'Belief and doubt', Research in Parapsychology 1972, Metuchen, N.J., Scarecrow Press, 1973, p. 189-200.

Beloff, J. 'Seven evidential experiments', Zetetic Scholar, July 1980, 91-94, 116-120.

Crumbaugh, J.C. 'A scientific critique of parapsychology', In Schmeidler, G (Ed.): 'Extrasensory perception', New York, Atherton Press, 1969, p. 58-72. (Reprinted from: International Journal of Neuropsychiatry, 2, 1966, 523-531.)

Hansel, C.E.M. 'ESP and parapsychology.  A critical re-evaluation', Buffalo, N.Y., Prometheus Books, 1980.

Honorton, C "'Error some place!"', Journal of Communication, 25, 1975, 103-116.

Honorton, C 'Has science developed the competence to confront claims of the paranormal?', Research in Parapsychology 1975, Metuchen, N.J., Scarecrow Press, 1976, p. 199-223.

Honorton, C. 'Beyond the reach of sense: Some comments on C.E.M.

Hansel's ESP and parapsychology: A critical re-evaluation', Journal A.S.P.R., 75, 1981, 155-166.

Johnson, M, 'Interview with Martin Johnson in 1979', (Partly published in Sokaren, 1981, in Swedish)

Kuhn, T.S. 'The structure of scientific revolutions', Chicago, University of Chicago Press, 1962.

Nicol, J.F. 'Comments to Beloff' (1980).

Pratt, J.G. 'Prologue to a debate: some assumptions relevant to research in parapsychology' Journal A.S.P.R., 72, 1978, 127-139.

Pratt, J.G. 'Parapsychology, normal science and paradigm change', Journal. A.S.P.R., 73, 1979, 17-28.

Price, G.R., 'Science and the supernatural', Science, 122, 26 Aug. 1955, 359-367.

Rhine, J.B. et al.  'Extrasensory perception after sixty years', New York, Holt, 1940.

Robinson, D. 'Letter', June 17, 1981.

Schmeidler, G.R. 'Parapsychologists' opinions about parapsychology', Journal of Parapsychology, 35, 1971, 208-218.

Schmeidler, G.R. 'Letter', April 15, 1979'

Schmeidler, G.R. 'Rhine's contributions to experimental methodology and standards of research', Journal of Parapsychology, 45, 1981, 11-23.

Scriven, M. 'New frontiers of the brain', Journal of Parapsychology, 25, 1961, 305-318.  Stanford, R.   'Comments to Beloff (1980).

Stevenson, I. 'An antagonist's view of parapsychology.  A review of professor    Hansel's ESP: A scientific evaluation', J. A.S.P.R., 61, 1967, 255-267.

Stevenson, T. 'Letter', May 7, 1979.

 

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1 All of these, except Dr. Bender, completed their selections already in 1979.