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).

General Relations of ESP to the Individual Subject

What Proportion of the General Population has shown Measurable ESP Ability? | Incidence of ESP Among Special Classifications | Summary

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

          THE DISCUSSION in this chapter is concerned with the question: Who has ESP ability? That is to say: What kind of people show ESP capacity and can the capacity be related to any general group characteristics? This presupposes, of course, some kind of restriction of the range of characteristics to be regarded. Mainly, the attempt has been made to find related features of general psychological, biological, anthropological, and social character. The more specific questions as to the conditions under which ESP occurs and its possible physical and mental relations will be considered in the chapters that follow.

What Proportion of the General Population has shown Measurable ESP Ability? [top]

The question of the proportion of individuals who show ESP ability has never been a primary one for investigation, largely because of the fact that statistical measures have been required in the experimentation done. The role of the individual can be isolated only with difficulty by means of such measures. Accordingly, it is impossible to express, with strict scientific accuracy, a percentage or proportion of persons tested who can be said to possess ESP capacity.

This does not mean, however, that nothing can be said about individuals and that no comparisons can be made. Obviously in such cases as those reported by Riess(1) and by Warner(2), for example, in which a single subject produces all the data and in which the critical ratios are very high, it may be safely concluded that the subject possesses ESP ability. On the other hand, in a study like that of Price and Pegram in which 66 subjects were used, 28 of whom gave results that yielded a critical ratio* (C.R.) of 2.5 or more, it cannot be said with complete accuracy that the 28 possess ESP ability and the others do not. According to the mathematics of probability, one of the 28 might be expected by chance alone to obtain results that exceed that criterion. Also, many of those failing to give a C.R. equal to or above the criterion of 2.5, yet giving positive deviations, might actually have got many of the cards by ESP. All that can be said with safety is that although a C.R. of 2.5 would be expected on the average by only 1 in 150 such subjects properly sampled, 28 out of 66 subjects actually did produce it. There need be no hesitation, then, in ascribing ESP ability to most of the 28 but the exact number cannot be determined.

(1) Reiss, Bernard F. "A Case of High Scores in Card Guessing at a Distance," Journal of Parapsychology, I (1937), 260-263.
(2) Warner, Lucien. "A Test Case," Journal of Parapsychology, I (1937). 234-238.
* The observed deviation divided by the standard deviation.

So much for the statistical limitations on giving a percentage of successful subjects. The psychological difficulties are even greater. As will be seen in later discussion, there is evidence of great variation of performance by the same subjects under different conditions and at different times. Also, the experimenter-subject relationship is apparently important. Some experimenters succeed in demonstrating ESP; others fail even with the same subjects and conditions. As long as there are variable factors entering into the estimate, any statement of percentages would have to be made with due consideration of limiting conditions.

Since these restrictions, statistical and psychological, must be imposed, there is little value left to whatever figures might be assembled. There is the further problem of getting the data on individual performance from the reports, many of which do not present the results of individual subjects. Data from the 25 reports issued since 1934, in which the figures of individual performance are available (this list includes both positive and negative results), show that the subjects achieving critical ratios of 2.5 or better represent about 18% of the number tested(3). This is between 1 in 5 and 1 in 6. which compares closely to the estimate of 1 in 5 made by Rhine in 1934(4). (The proportion, in view of the above criterion, might be rated as indicated.)

(3) In the group of reports, upon which these tentative figures are based, there is one which reports only one C.R. of 2.5 or better from a group of 124 subjects. In the work reported by Rhine in 1934 in Extra-Sensory Perception. (Boston: Bruce Humphries), 27 subjects were given as many as 100 trials each and 18 gave a C.R. of at least 2.5. There were, however, a total of 206 subjects estimated to have been tested in all, most of these being given but a few preliminary trials in group tests.
(4) Forum Magazine, Dec. 1934, p. 369.

The estimate of the distribution of ESP subjects can serve only a tentative purpose for the experimenter who might find broad comparisons of advantage. For example, there are larger percentages reported by Price and Pegram, L. E. Rhine, and Bond for children than are to be found for adult subjects. Again, larger percentages of subjects are reported for the informal procedures first used by J. B. Rhine in his earlier work than for the more elaborate experimental conditions which developed later(5).

(5) This raises two questions: (a) whether absence of precautions accompanied the informality and might explain the results; or (b) whether the psychological advantage of the informality contributed the higher percentage. This point is the topic of a research report still in manuscript, the substance of which is as follows: 40 student subjects from psychology classes were to be given formal, routinized tests conducted by appointment. Ownbey, Pegram, and Rhine participated as experimenters. The unscreened BT technique was used with hand-stamped, carefully selected cards. Actually, 43 subjects were tested but examinations interrupted the pre-arranged schedule so that instead of the thousand trials for each subject originally projected, the average at the end of the year was only 425. At this point, only one subject even approximated the C.R. of 2.5 (2.44). All three experimenters had, with the use of precisely the same technique and exactly the same precautions, obtained significant results with several subjects under the more informal conditions either before or after the work in question. On the other hand, relaxing the precautions gives no assurance of high scores. Cason tested subjects with the GESP procedure with the agent and percipient in sight of each other in the same room; and, apparently to his surprise, he did not obtain extra-chance scores.

In citing the above estimates for the proportion of subjects showing C.R.'s of 2.5, it has been emphasized that such estimates must be strictly limited to the conditions that prevailed. What percentage of people possess ESP ability under any other conditions can, at this stage, only be conjectured. The general impression among experimenters is that (a) the limitations upon successful performance and, accordingly, the distribution of successful scores is more a matter of personal adaptation to the test situation than a matter of native ability; and (b) the number of subjects showing such ability might be greater if natural and spontaneous life situations could be approximated without undue restriction by laboratory routines. These must, of course, remain suggestions until more delicate tests are applied which will reliably measure ESP under a much wider range of conditions than is possible at present.

Incidence of ESP Among Special Classifications [top]

The necessity of using statistical methods of study which offers difficulty in the determination of individual differences also makes it hard to correlate the phenomenon in question with characteristics of the individual. Until it is determined who has the ability, it is, of course, impossible to find out what the gifted individual is like. But broad groupings and classifications of the general population may with some safety and success be considered to the extent of statistical comparison.

Sex Differences. To begin with, it may be said that the investigations of ESP have established the fact that both sexes have demonstrated ESP capacity under the very best conditions. In the Pearce-Pratt series, the subject was a man; in the Murphy and Taves and the Pratt-Woodruff series, the group was mixed; in the Warner and Riess reports, the subjects were women. In the long distance telepathy series, two were women and one a man. Of the eight major subjects of the Rhine monograph(6), five were men and three were women. The numbers of men and women are about equally divided throughout most of the ESP reports.

(6) Rhine, J. B. Extra-Sensory Perception. Boston: Bruce Humphries, 1934.

Thus far there has been no demonstration of a consistent difference in scoring rate between the sexes; there are outstanding subjects of both sexes and the numbers of these are comparable. Certain investigators working with both sexes have not even referred to comparative figures on the sexes where mixed groups were used, thus indicating that no difference was outstanding to the extent of being noticed. In view of this, it is safe to say that it is indicated that there is no marked difference between ESP performance of the sexes.

Age Ranges. On the question of age, it is indicated that both children and adults possess ESP ability. In the work of L. E. Rhine, the younger subjects, from three to seven years, contributed most of the deviation. Significant results are reported by Rice(7) and by an anonymous scientist (9) for two subjects approximately sixty years of age. The majority of the subjects used, however, would range between the ages of seventeen and thirty-five. Price and Pegram give a tabular summary of the age ranges of their subjects having C.R.'s of 2.5 or greater. This material is reproduced in Table 16 (see below). All four of the age groups have large percentages of subjects with C.R.'s equal to or greater than 2.5. The age group with the largest percentage is that between eleven and fifteen years in which 54 per cent of the 28 subjects tested for that group have C.R.'s equal to or above 2.5. Next came the period of sixteen to twenty years, inclusive. This does not coincide with the age relations derivable from L. E. Rhine's work just mentioned. Her group of children, aged eight to fifteen, inclusive, should compare favorably with the eleven to fifteen, inclusive, of the Price and Pegram work. But as a matter of fact, the Rhine group, from eight to fifteen, was insignificant while, in the Price and Pegram report, that group was the highest of the series. From this it is indicated that age is at least not a dominant factor in determining success. It is suggested that the differences in results shown between the age levels in the two reports just mentioned are due either to the differences in the groups studied or more probably to social factors in the different experimental situations.

(7) See; Pratt, J. G. "The Work of Dr. C. Hilton Rice in Extra-Sensory Perception," Journal of Parapsychology, I (1937), 239-259.

The Age Ranges of Individually "Significant Subjects"

Age Number of Subjects Tested Number of Individually "Significant Subjects" Per Cent "Significant"
6-10 7 2 29
11-15 28 15 54
16-20 22 9 41
21-35 9 3 33

Blindness. Two points are indicated regarding blind subjects and ESP ability - both arising from the work of Price and Pegram and a control series later by Price(8): first, that blind subjects (some at least) have the ability in demonstrable degree; second, that they are not significantly superior to the comparable seeing subjects tested by Price. The comparative study involved 66 blind and 40 seeing boys. Both groups were institutionalized and of comparable age level; both were tested by the same experimenter and given approximately the same number and type of tests. The blind averaged slightly higher but not significantly so.

(8) Price, Margaret M. "A Comparison of Blind and Seeing Subjects in ESP Tests," Journal of Parapsychology, I (1938), 273-286.

Patients in Mental Hospitals. Working with psychopathic patients in the Hudson River State Hospital and using a form of the STM technique, Shulman(9) found that one classification of subjects, the manic-depressive depressed, gave a significantly positive average deviation. He also found the nine involutional melancholia patients tested gave a markedly low average, 4.72 in 290 runs. In a completely independent series at the New Jersey State Hospital at Morristown, Van Wiemokly, working with subjects from only three classifications, got results which closely approximated Shulman's averages for the corresponding classifications. His average for four involutional melancholia patients for 100 runs was 4.77. The work of Shulman and Van Wiemokly on subjects under the involutional melancholia classification, if combined and regarded separately, gives a negative deviation with a C.R. of 2.6. Van Wiemokly did not test manic-depressive depressed patients.

(9) Shulman, Robert. "An Experiment in Extra-Sensory Perception, with Sounds as Stimuli," Journal of Parapsychology, II (1938), 322-325.

Price(10), using 49 patients in the Ohio State Hospital as subjects, obtained positive instead of negative deviations with the involutional melancholia patients. But the reports are not seriously in conflict. Price found that among the classifications tested by both her and Shulman, the manic-depressive depressed patients stood out with the highest average performance. And the involutional melancholia subjects, which were lowest for the first two reports, were but slightly (.01 average) above the lowest in Price's series. The most important difference is that positive deviations were obtained by Price among all the principal classifications. The methods used were blind matching with covered key cards and screened ESP shuffle or deck matching. Counting methods were followed instead of recording, with a re-count of hits after each run to effect a check on possible errors.

(10) Price, Margaret M. "An Experimental Study of ESP Capacity in Psychopathic Patients." [Unpublished MS.]

In view of the degree of confirmation which these three reports do give to each other, in spite of important differences, the rating of indicated may he given to the hypothesis that persons diagnosed as psychopathic are capable of ESP performance.

It is further indicated by the foregoing studies, taken together with studies by Price with normal subjects, that psychopathic patients and normal persons do not show a reliable difference in their ability to perform in the ESP tests. In point of fact, the average obtained by Price, 5.53, is approximately that which she obtained with normal subjects in earlier studies.

The outstanding relationship encountered in Price's study of psychopathic patients was the correlation found between the ratings of the patients (in the ward records) for degree of co-operation and their ESP performance. Groups with the three ratings, co-operative, apathetic, and irritable, are ranked in the same order with regard to success in ESP scoring. The results are summarized in Table 17.


Degree of Co-operation Number of Subjects Number of Trials Average
Co-operative 19 18,475 5.75
Apathetic 15 12,500 5.46
Irritable 15 11,375 5.32
Total 49 42,350 5.53

Hypnotizability. It was shown in Chapter I that there is historic ground for associating ESP phenomena and hypnosis; there is also a common association of the two in the minds of many of those offering suggestions to investigators in the field. Hypnotizability(11), however, is not correlated with outstanding success in the later period of investigation (and in the earlier period it may have been incidental, since no control was made on this aspect). Rhine(12) found that several of his major subjects (e.g., A. J. L. and H. P.) were not hypnotizable, although some of them were. In his earlier work (with Lundholm) a number of hypnotizable subjects were tested with insignificant (though positive) deviations in ESP tests. The question whether the hypnotic state is advantageous in ESP test procedures is discussed later; but the absence of relation between ESP scoring and hypnotizability is indicated, to say the least.

(11) Hypnotizability, like ESP capacity itself, is not measurable, as yet, in absolute terms, and must be regarded as dependent at least (a) on the experimenter attempting to induce it; (b) on the subject's motivation; and (c) on the experimental situation (persons present, purpose of experiment, etc.).
(12) Rhine, J. B. Extra-Sensory Perception. Boston: Bruce Humphries, 1934.

"Psychics." It is frequently suggested that professional "psychics" have superior endowment in ESP. Coover(13) got negative results with fourteen mediums. At the same time, he reported on ESP tests with normal student subjects to the extent of 10,000 trials with statistically significant results. The significance of his data was not recognized by Coover, but has been confirmed by others (14, 15, 16, 17). Hyslop gave one "psychic" a series of ESP tests and obtained results giving a C.R. of 1.34. Rhine examined a professional medium in both telepathy and clairvoyance tests, in trance and waking states, and obtained significant results; but in later pre-shuffle card calling tests, as stated above, obtained only chance averages, as did Goldney and Soal still later in the GESP and clairvoyance tests working with the same medium. On the whole, there is nothing to indicate outstanding ability among those of the professional occult field who have been tested. Too few have been examined for generalization with any assurance. It might be said, however, to be indicated that in the ESP test "the professional psychic" is not a superior subject. The paucity of cases itself supports this indication. The professional clairvoyant may, of course, find some handicap in transferring abruptly to a laboratory routine, and this possible handicap should be considered before final conclusions are drawn.

(13) Coover, John E. Experiments in Psychical Research. Palo Alto: Stanford University Press, 1917.
(14) Carrington, W. W. "Some Early Experiments Providing Apparently Positive Evidence for Extra-Sensory Perception", Journal of the SPR, XXX (1938), 295-305.
(15) Rhine, J. B. Extra-Sensory Perception. Boston: Bruce Humphries, 1934.
(16) Thouless, R. H. "Dr. Rhine's Recent Experiments on Telepathy and Clairvoyance and a Reconsideration of J. E. Coover's Conclusions on Telepathy," Proceedings of the SPR, XLII (1935), 24-37
(17) Hart, Hornell. Science Beyond the Senses. [Unpublished MS.]

Intelligence. Another instance of the absence of relationship between ESP ability and personal characteristics may be pointed out as indicated; namely, the relation between ESP and intelligence. Bond found no significant correlation between intelligence and performance in her study of 22 retarded school children. Drake's subject was of subnormal intelligence. At the other extreme, one of Rhine's major subjects was an exceptional student; on the whole his subjects represented a good cross section of the university student group. Were there any outstanding connections between intelligence and ESP, the experimenter constantly looking for some clue to the identification of gifted subjects would quickly discover the relation with so commonly measured personal characteristic as intelligence. This would be especially obvious in colleges, where the existence of such ratings is a matter of common knowledge. The very absence, then, of any suggestion of such a relationship is testimony of considerable weight that there is none. Successful ESP subjects have ranged from distinguished scientists and literary people to a point as far down the scale of intelligence as will permit investigation.

Performance during Illness. Rhine(18) reported the incidental observation that two of his major subjects obtained markedly lower score averages during attacks of tonsilitis. An anonymous scientist(19) reported the finding of negative deviations, as contrasted with his normal significantly positive deviations, when suffering from illness diagnosed as "sick headache." Riess's subject had her remarkable series interrupted by the necessity for medical treatment of what the physician diagnosed as hyperthyroidism. Following a period of treatment for this condition, a series of tests averaged very little above chance. Drake's subject was, on the contrary, suffering from hypothyroidism and as treatment proceeded for this disorder, his scoring ability declined.

(18) Rhine, J. B. Extra-Sensory Perception. Boston: Bruce Humphries, 1934.
(19) Anonymous. "Do you Think Out Loud?" Popular Science Monthly, CXXXIII (1938), 70-71.

Superficially, it might appear that hyperthyroidism had contributed to the excellent performance of Riess's subject and that the treatment in itself destroyed the ability. While the suggestion is worthy of further investigation, it is very probable that other concomitant circumstances might be found in the life of the subject at the time, and these, if brought into focus, would also appear to be related. When the case of Drake's subject is taken into account, it seems the more unlikely that the particular disorder attributed to Riess's subject, assuming the diagnosis to be correct, was involved in a primary way. The decline or sudden loss of ability will be seen in later paragraphs to be an expected occurrence in this field of exploration, and to associate the circumstances of treatment with the loss in these two thyroid cases would be especially hazardous until further work on the possible relations involved, together with controls, is achieved. The other instances mentioned suggest interference with performance, but the production of a negative deviation, in the one case, suggests that the interference has to do with motivation instead of the ability. The ability is simply inverted in its operation. Summarizing all the observations available to ESP and illness', it would appear to be suggested that there is no fixed relation between physical disorder and ESP performance.

Summary [top]

A brief survey has been made of the literature on ESP for any special limitation that might be found in the distribution of ESP capacity among the general population, with a view to the discovery of some general characteristic of the gifted subject. But so far as the reports available are concerned, there is nothing to indicate any reliable relation between any grouping or classification of subjects from the general population and success in ESP performance. The survey has covered the literature bearing on the possible relations between ESP performance, on the one hand, and sex, age, blindness, mental abnormality, hypnotizability, mediumship, intelligence, and certain physical illnesses, on the other; but no reliable relation has to date been found(20). The absence of relationship has, however, been pointed to with more or less certainty for the various possibilities examined. It is perhaps of equal importance to know either of the absence or of the presence of a relation if this is the verdict of the facts. For it is essential to the exploratory program that the limitations of the principle or phenomenon under examination be determined. The discovery of the limits in distribution of ESP ability among the general population is only to be found by getting at the "absence" as well as the "presence" side of the project. However, a much more extensive investigation on a wider front will have to be conducted before full knowledge of the relations (or absence of them) of ESP to the individual's characteristics is attained.

(20) The indication of a relation between co-operation and ESP test performance is the only positive relation having even that status; and until a full report is issued, it cannot properly be stressed.


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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