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
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
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
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.