Duke Experimenters

This article was collectively written by J. B. Rhine (Professor of Psychology), J. G. Pratt (Instructor in Psychology), Charles E. Stuart (Prince Memorial Fellow), Burke M. Smith (Graduate Research Assistant) and Joseph A. Greenwood (Assistant Professor of Mathematics) of the Parapsychology Laboratory Department of Psychology at Duke University. It appeared in "Extra-Sensory Perception After Sixty Years: A Critical Appraisal of the Research in Extra-Sensory Perception" (1940, Henry Holt and Company, New York).

Introduction: Relations and Evidence

Modification of Criteria | A Rating Scale

- J. B. Rhine, J. G. Pratt, C. E. Stuart, B. M. Smith and J. A. Greenwood -

          AT THIS point of the book a definite change of viewpoint is introduced. Hitherto, the question has been: Does ESP occur? During the next five chapters it will be: What is the nature of ESP? or in other words: What relations does the process of ESP have to other more familiar processes and relations?

Throughout Part III the conclusion reached at the end of the preceding chapter will be taken literally, and the occurrence of ESP regarded as established. This is not to suppose that it will be so accepted by everyone, or even by all of those who have carefully followed the evidence and the argument through the preceding chapters(1). However, it is not necessary that the reader accept the ESP hypothesis as a fully established one to find the chapters of Part III of interest. Indeed, there doubtless are critical readers, particularly those who find it necessary that an hypothesis be made to appear reasonable before any amount of evidence suffices to establish it for them, who will find the following treatment of relations of considerable help in reaching a decision on the hypothesis itself.

(1) Nor is this position to be construed as implying that any further work contributing merely to the strengthening of the ESP hypothesis would be without value.

Modification of Criteria [top]

Up to this point, the question at issue has been one on which an affirmative answer was a priori highly improbable, and one which therefore required extremely high standards of evidence and an unusual amount of confirmation for establishment. The recognition of this requirement by investigators of ESP has led to the pyramiding of precautions until, in the most careful of the experiments, the conditions imposed were far more stringent than those expected of scientific experimentation in general.

But since this development of safeguarding features reached its highest point largely in recent years and these most advanced conditions characterize only a small part of the total published research, an important question arises, namely: Is this fraction of the total results all that may be of value in weighing the evidence bearing upon the further questions that are now to be considered regarding the nature of ESP? Or are there experimental results which failed in some degree to meet the exceptional standards necessarily placed upon the evidence while the occurrence of ESP was primarily in question but which, now that that question is settled, can be found acceptable when measured by more customary standards?

In attempting to answer this question, it is of importance to make clear what use is intended to be made of the evidence. The purpose of this study of the relations of ESP is to take stock of what has been discovered, incidentally or otherwise, regarding the properties, characteristics, and requirements of the ESP process, primarily in order to guide the investigator in future exploration. With this objective of getting a working chart that will indicate the most profitable and promising lines of study for the future, it would be safe as well as advantageous to summarize not only the best of the evidence but also any research that might contain important indications and suggestions. It would likewise contribute to the present purpose to discuss work as yet unpublished (and therefore not mentioned before) when such experiments have any bearing upon particular ESP relations in any important respect.

This is not, however, as might at first appear, to discard the canons of evidence which have guided the discussion hitherto. The shift in standards is a limited one dealing both with a different set of problems and, as has just been indicated, a very different purpose. As will be seen by a simple example, it was quite another question to ask originally: Does ESP occur? than it will be, now that ESP is taken to be established, to ask: Is there any difference between men and women with regard to the capacity for ESP? The first question clashes with all the natural conviction of a doctrine of long tradition. The second, once the first question is answered affirmatively, meets with practically no a priori bias or resistance. As indicated above, the first question demands extremely high standards of evidence. The second is comparable to the thousands of problems of comparison with which research in general is concerned. Most of the relations which are considered in these chapters are similar in character to the illustration (the relation between ESP and sex differences) just used.

A Rating Scale [top]

It will, perhaps, be of some help in evaluating the evidence for a particular relation to set up a scale of approximate rating standards for the judgment of each hypothetical relation considered; i.e., as to how far it may be regarded as successfully demonstrated, positively or negatively. Any such standards must obviously be arbitrary, but at the same time the attempt will be made to state criteria of widest general acceptance for each point.

A rating scale of three grades, with characterizing terms, is adopted to represent different degrees of acceptability of the hypothetical relationship which is the object of investigation. The criteria by which these ratings may be assigned to the various ESP relations have been fixed as the following:

An Established Relation. Ordinarily a relation may be regarded as established if it is derived from at least two experimental series of ESP tests: (a) at least one experiment must have yielded results that are not explainable by any of the alternative hypotheses listed in Chapter V (at present this would limit the available evidence to the six series presented in some detail in Chapter VI); (b) the second, supporting experiment may have been done with safeguards excluding visual cues in clairvoyance tests, and both visual and auditory cues in GESP or PT tests (at least to the extent of having agent and percipient in different rooms with closed doors between).

If the hypothetical relation be one that runs counter to earlier findings or to strongly entrenched belief among scientists., it will be necessary to have two independent series conducted under conditions that completely meet all counterhypotheses.

An Indicated Relation. A single experimental series yielding significant results, meeting the criteria given under (b) above, suffices to meet this criterion. If the hypothetical relation is contrary to previous findings, there are required at least twice as many favorable series as there are opposed, assuming equal quality of safeguards and adequacy of experimentation. Again, if there are a number of independent experimental series failing to meet the criterion set (namely, of excluding visual cues for clairvoyance tests; visual and auditory cues for GESP and PT) and there are at least three such series in agreement, the hypothetical relation in question may be regarded as indicated.

A Suggested Relation. Experimental findings that do not meet the higher ratings fall naturally under this heading unless they are in contradiction to other experimental results or contrary to general expectation. In such case, two favorable findings to one adverse conclusion are required.

Established relations are, of course, answers to problems effectively solved, and in this discussion the relations with different degrees of establishment are essentially problems which are at different stages on the way toward solution. They are listed and considered here in no sense as filed claims of accomplishment, but as an outline of partial and potential discovery. The emphasis for sixty years upon the primary question of the occurrence of ESP, with the continual distraction of controversy over this initial issue, has caused these questions to be neglected. At the same time, there has been a heavy drainage of research time and interest into the related studies of the various psychical research groups. In consequence, little direct effort has been made to push on into the problems dealing with the nature of ESP itself. Yet every step in this direction, whether incomplete or established as it stands, may be important for the experimenter to know in planning further research.

The relationships (and possible relationships) to be discussed may be arbitrarily grouped as follows: (1) What are the general relations of ESP to the individual subject? (2) What are the general test conditions under which ESP occurs? (3) What physical relations has ESP been found to have? (4) Where does ESP come into the present body of psychological knowledge?


The article above appeared in "Extra-Sensory Perception After Sixty Years: A Critical Appraisal of the Research in Extra-Sensory Perception" (1940, Henry Holt and Company, New York) by J. B. Rhine, J. G. Pratt, C. E. Stuart, B. M. Smith and J. A. Greenwood.

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