PK Effect on Pre-Recorded Targets


(Originally published in The Journal for the American Society for Psychical Research Vol.70, July 1976)

ABSTRACT: In three PK experiments the random events to be affected were generated and recorded in the absence of both subject and experimenter. The subject became involved only later when the pre-recorded events were played back to him.

The first experiment used an electronic random number generator with hit probability = 1/64. In the first part of the test the hits were displayed immediately as weak clicks on which the subject had to concentrate. In the second part the clicks were first recorded on magnetic tape and later played back to the subject. In both cases an increase in click rates above chance expectancy was observed (P=.001).

In the second experiment loud clicks were randomly (hit probability = 1/2) channeled to the right or left ear while the subject tried to enforce an increased click rate at the right ear. Half of these events were momentarily generated while the other half came from a replay of an earlier recording. Each recording was used for four sessions so that subjects spent four times as much effort on each pre-recorded event than they did on each momentarily generated event. The scoring rates on the pre-recorded and momentarily generated targets were 52.9% and 50.8% (P=.005 and .05, respectively). This confirms the existence of a PK effect on pre-recorded targets and suggests that repeated replay of the same targets may lead to higher scoring rates.

In the third experiment the task was the same as in the previous one, but the binary events came from an "easy" generator with a hit probability of 7/8 and a "difficult" generator with a hit probability of 1/8. A pre-recorded sequence of +1's and -1's determined the order in which the easy (+1) and difficult (-1) generators were activated. The subject was successful if in this sequence he obtained an excess of +1's, and in addition he could improve his score by affecting the easy and difficult generators directly. The results were not significant enough to permit a detailed comparison between the direct PK effect and the PK effect on the pre-recorded sequence, but the latter was confirmed at the .05 level.


Consider the following experiment: A random number generator is activated to produce a string of N binary numbers. These numbers are automatically recorded on magnetic tape, paper punch tape, or some other reliable recording medium. Nobody is present during this generation and recording, and nobody looks at the data until at some later time the recorded sequence of "heads" and "tails" is played back to a subject in a PK test situation. During the slow playback each recorded head or tail makes a red or green lamp light up while the subject tries mentally to enforce an increased lighting rate of the red lamp.

One might think that in this situation the subject could not succeed because the decision as to how many heads and tails will appear has already been made before the test session. But one can also present arguments that PK might still operate, and that, furthermore, such PK tests with time displacement could give some interesting new insights into the physics and psychology of psi. Let us look at some of these arguments.

A Mechanism of Subconscious Goal-Oriented PK

Many earlier studies (e.g., Schmidt, 1974; Stanford, 1974) suggest that PK is goal-oriented and is largely activated by subconscious factors. Therefore, in the hypothetical experiment mentioned above, the subject and/or the experimenter might subconsciously initiate a PK mechanism at the time when the binary numbers are generated. And this could lead to a successful outcome of the test. In this interpretation, a PK effect on prerecorded targets could occur even if PK acts in a causal manner like the other known forces of nature; i.e., we would not have to assume for PK any of the features of time independence which are familiar to us in the realm of ESP.

From this viewpoint it would be interesting to measure in the experiment the subject's and the experimenter's mood (or some other physiological-psychological parameter) at the time of target generation and also at the time of the test session to see how these measures correlate with the PK score.

Possibility of a Noncausal PK Mechanism

When the time independence of telepathy and clairvoyance became apparent, i.e., when the reality of precognition was established, this seemed quite contrary to common sense. People asked by what "mechanism" the outcome of a future random event could cause something (the subject's correct response) to occur in the present. But in spite of this conceptual difficulty, precognition continues to exist, and rather than wondering what is wrong with precognition, we should ask what is wrong with our common sense.

The fault with this "common sense" is that it is based on the picture of a causal world in which a cause may produce some later effect, but not vice versa. This picture seems applicable to the vast majority of phenomena observed in everyday life and in the physics laboratory, but not to precognition.

If ESP is noncausal in the sense that a future random event may produce an earlier effect (the subject's correct response), we may have to consider the possibility that PK is noncausal in the sense that a present random process may be affected by the subject's PK effort made at some future time. In view of the close relationship between PK and ESP (Schmidt and Pantas, 1972), one might even be surprised if PK did not share the feature of time independence with ESP phenomena.

Implications of a Theoretical Psi Model

Recently a mathematical model of psi was discussed (Schmidt, 1975) in which precognition, PK, and other forms of psi appear as outcomes of one unifying psi principle. This model may be too simplistic, but it is logically self-consistent and thus permits us a full discussion of those vexing aspects of psi which seem to be contrary to common sense.

This model predicts in particular that the score in a PK test with time displacement should be essentially the same as the score in a corresponding conventional PK test. The outcome of the test should depend only on the test conditions (such as mood of subject and experimenter, nature of feedback, etc.) at the time of playback, but not on the conditions at the time when the targets were generated. A quite specific and easily testable feature of this model is, furthermore, that the repeated playback of a prerecorded target sequence to the subject should lead to an increase of the PK scoring rate.

Possible Connection with the Reality Problem of Quantum Theory

No development of modern science has had a more profound impact on human thinking than the advent of quantum mechanics. Wrenched out of centuries-old thought patterns, physicists of a generation ago found themselves compelled to embrace a new metaphysics. The distress which this reorientation caused continues to the present day. Basically, physicists have suffered a severe loss: their hold on reality (Bryce S. DeWitt, 1971).
In the hypothetical experiment mentioned above, it seems intuitively obvious at which time the random decisions are made: when the generator is activated and the outcome (head or tail) is recorded. The experimental findings of quantum physics raise some doubts, however, whether this common-sense judgment is meaningful. We may see the origin of the problem by considering first the special random number generator shown in Figure 1.

Fig. 1 belongs here

Fig.1. A binary random number generator built from an electron gun, a semitransparent mirror (M) and two electron counters.

This generator consists of an electron gun which emits, say, every minute one electron toward a semitransparent mirror M, so that each electron has a 50% chance of penetrating the mirror and entering the tube T1 and a 50% chance of being reflected into the tube T2 If we install electron counters C1, C2 at the end of these heavy metal tubes T1, T2, then, under somewhat idealized conditions, each arriving electron will be registered by one of the counters. It will never happen that an electron gets split into two parts so that each of the counters registers half an electron, because no half electrons exist in nature. Thus we have an ideal binary random generator: every minute one of the two counters registers an electron and the decision which counter will respond next is made by an elementary quantum process which should be determined by pure chance.

It may appear intuitively obvious that the random generator has made a decision whenever an electron has passed the mirror M and reached the entrance to the tubes. This is because an electron which has entered, say, T1, cannot escape through the wall of the tube and is thus bound to activate the counter C1. But this argument appears inconsistent with another experiment:

Fig.2 belongs here

Fig.2. Setup for an electron interference experiment.
Suppose we remove the counters C1 and C2 and let the emerging electron beams converge on a screen S (see Figure 2), and we then measure with a large number of electron counters where each electron arrives at the screen. If we continue the experiment for many hours, emitting one electron per minute, then we can map the average particle arrival density for each point of the screen. The experiment shows that the electrons arrive over a spread-out area and that the arrival density fluctuates along the X-axis as indicated by Figure 3a. This pattern can be interpreted only if we consider each electron as a wave which traveled through both tubes simultaneously and thus produced an interference pattern at the screen. This interpretation is supported by the fact that the closing of either one of the tubes changes the arrival density to a smooth distribution indicated by Figure 3b.

Figs. 3a. and 3b. belong here

Fig. 3a (above) Electron arrival density in the interference experiment.
Fig. 3b. (below) Electron arrival density if on e of the two tubes is blocked
Thus in the arrangements of Figures 1 and 2 respectively, the electrons seem to behave differently when they reach the tubes. It appears that in Figure 1 each electron enters only one of the tubes while in Figure 2 it travels as a wave through both tubes simultaneously. The odd feature of this result is that an electron, at reaching the entrance of the tubes, should not yet "know" whether it will encounter the arrangement of Figure 1 or Figure 2. Indeed, the experimenter might even change from one setup to the other while the electron is already inside the tubes.

The parapsychologist might feel tempted at this stage to ascribe some "precognitive features" to the electron, but in extensive experimental and theoretical studies over the last four decades physicists have found no indication that the unusual behavior of the electron could be utilized to predict the future in the manner human subjects can predict future random events. Quantum theory has coped with the paradox successfully, not by invoking some noncausal mechanism, but by a change in the concept of "physical reality."

In the arrangement of Figure 1 we feel intuitively that after the electron has reached the tubes it must be "really" in one or the other tube. But in the quantum mechanical formalism the physical state of the system is at this stage a "superposition" of two possible states, one state with the electron in T1 and one state with the electron in T2. Nature has not yet decided for one of these two possibilities, and that is why we can still shift to the test arrangement of Figure 2 and observe an interference effect between two states. The decision as to which one of the two possibilities is "real" occurs when the experimenter makes a measurement with the electron counters and finds the electron in one or the other tube. It appears unreasonable to even talk about physical reality (in the sense that the electron must be really" here or there) before the experimenter has made his observation (to find out where the electron is). "Reality" is only what the experimenter observes.

The loss of a physical reality which exists independently of the observer as an intuitively obvious concept may not be restricted to small systems like single electrons, but may carry over into the macroscopic world: assume that in the experiment of Figure 1 the counters are connected to an automatic punch tape recorder so that each electron received by C1 or C2 is recorded as a hole on either the right or the left side of a paper tape. Then, after the electron has reached a counter, but before an observer has taken notice of the results, the current state of the system is described by quantum theory as a superposition of two possible states: one state where the counter C1 has recorded a particle and a hole is punched on the right side of the tape, and one state where the counter C2 has recorded the electron and a hole is punched on the left side of the tape. These two states are coexistent; nature has not yet decided for one or the other. The decision is made when the experimenter takes notice of the results.

Many attempts have been made to modify or to re-interpret quantum theory so that the concept of an absolute reality could be saved at least at the macroscopic level. But with the present tools of physics we have no means of testing whether the outcome of a random process becomes finally decided when the result is macroscopically recorded or when the human observer takes notice of the results.

With the tools of the PK tests we might have another access to the reality problem. We might tentatively assume (somewhat naively, in view of the noncausal aspects of PK) that a present PK effort can only affect random processes of which the outcome is not yet decided. (We could even try to define physical reality by the requirement that the state of a physically real system cannot be changed by PK efforts.)

From this viewpoint the comparison of PK on random processes before or after they have been macroscopically recorded (i.e., the comparison between conventional PK and PK on prerecorded targets) seems particularly interesting. If the described interpretation of quantum theory is right, then the PK effort after the recording should be equally successful, because at this stage nature has not yet reached a decision on the outcome. Thus the PK effect on prerecorded targets appears as a natural consequence of the conventional PK effect. An interesting modification of the experiment results if the PK effort is made after some human experimenter has looked at the outcome. This latter case is not studied, however, in the present report.


The first encouraging PK result with prerecorded targets was obtained by the present writer in 1971 at the Institute for Parapsychology in Durham, North Carolina, with Mr. Lalsingh Harribance as subject.

As a first step in this experiment, a fast binary random generator was automatically activated to generate many blocks of 201 binary numbers. The generation rate was 20 numbers per second and the blocks were separated by 20-second intervals. The "heads" and "tails" were registered as clicks in the right and left channels of a stereo cassette recorder. In this manner six "primary" tapes were prepared with an average of about 140 blocks per tape.

As a next step the first three primary tapes were copied on one-channel tapes so that each head or tail appeared on these "secondary" tapes as a weak or a strong click, respectively. They were then given to the subject to take home. He was instructed to play each tape once, to listen carefully to the weak clicks (while ignoring the strong clicks as far as possible), and to enforce an increased occurrence of weak clicks. The subject was encouraged to spread the test over many days and to take frequent breaks.

The heads and tails on the corresponding primary tape were electronically counted only after the subject had listened to a whole tape. The recovery of all clicks could be verified since the total number of clicks in each block was known.

In order to evaluate the results, the number of successful runs (block with more heads than tails) and the number of unsuccessful runs (block with more tails than heads) were counted. A total of 236 successful runs and only 189 unsuccessful runs were found, which is suggestive (CR = 2.38) of a PK effect on the prerecorded targets. Note that the subject never got in touch with the primary tapes on which the evaluation was based.

This type of experiment, where the subject works at home without the presence of an experimenter, might have many psychological advantages. It might provide a convenient means of channeling psi effects from the quietness of the subject's living room into the laboratory.

The other three prerecorded primary tapes were played back to the subject directly in the laboratory. Feedback was given by an instrument needle which was moved by each head or tail (as they were replayed from the tape) one millimeter to the right or to the left, respectively, while the subject tried to make the needle move to the right. The result of this part of the experiment was 218 successful runs and 189 unsuccessful runs (CR = 1.44). The total experiment gave a CR of 2.71 in favor of the existence of PK with pre-recorded targets.

The experiment had to be discontinued for technical reasons, but in 1972 some other pilot tests were carried out. Two of these studies, with Mr. Lee Pantas and Dr. E. F. Kelly, respectively, as experimenters, again gave encouraging results.

In these studies a four-choice random generator was used. The generator was automatically activated to generate a long random sequence of the numbers 1, 2, 3, and 4. This sequence was stored on paper punch tape. Nobody looked at the data until these numbers were read back in the test session by an electromechanical paper tape reader.

During the test session the subject sat in front of a panel with four lamps. Whenever he pressed a button the tape reader read the next number on the tape and made the corresponding lamp light. The subject's task was to make the lamp corresponding to the number 4 light with increased frequency. Thus he could succeed only if the prerecorded tape contained an increased number of 4's. The subject's score was automatically registered during the test, and could also be verified by another replay of the tape.

In his experiment Mr. Pantas compared the score of one subject, M. S., who had been particularly successful in previous tests, with the score of an unselected group of subjects. In both cases the targets came from the same long tape of prerecorded numbers. The 4100 trials made with M.S. gave a hit deviation of +72 (CR = 2.6), whereas the unselected croup in 4700 trials scored near chance (deviation of -7). After the completion of the experiment the unused part of the tape was evaluated by computer and showed no significantly increased number of 4's (deviation of +20 in 52,730 trials). Thus only the part of the tape which was used in the PK test with the special subject showed a significantly increased occurrence of 4's.

Dr. Kelly used the same test arrangement, but he had only one subject, Mr. Bill Delmore, who has obtained outstanding scores in experiments with different researchers. In a total of 8930 trials the deviation in the number of hits from chance expectation was + 158 (CR = 3.86).

These experiments are presented only as suggestive pilot studies, and it is not possible to assess the significance of the results rigorously because we do not have complete records of similar experiments (which were mostly aborted at an early stage) which did not produce positive scores.

The three experiments to be reported below, however, form a complete record of all confirmatory PK studies with prerecorded targets performed so far by the writer. Each of these confirmatory studies was begun after a previous pilot test had indicated that the conditions for observing PK were favorable in the given psychological-physical setup. The length of each confirmatory study and the main method of data evaluation were specified in advance.


This study was begun as a conventional PK experiment. After a pilot test and a confirmatory series had given significant results, a second series of tests was added, with the only difference being that the PK targets were recorded in advance of the test situation.

The Conventional Part of the PK Test Let us consider first the conventional part of the experiment. In this experiment an electronic random generator with p = 1/64 and q = 63/64 was used. For each test run the generator was automatically activated, at the rate of 10 trials per second, until a hit (p = 1/64) was obtained. Then the generator stopped and the hit was displayed to the subject through headphones as a weak click.

A display counter advanced with each trial made so that the reading of the counter at the end of a run gave the number R of trials which had been required for obtaining a hit. The chance expectancy for R is R~ = 64 (corresponding to an average run length of 6.4 seconds) and the chance probability for a particular R to occur is easily seen to be P(R) = p*q^(R-1), with p = 1/64, q = 63/64.

In this experiment an attempt was made to guide the subjects' PK efforts at a subconscious level such as to increase the hit probability; i.e., to reduce the average length of a run. The subjects were not aware of this goal but they were instructed to listen very carefully to the barely audible clicks so that they would not miss any of the clicks terminating a run. The challenging aspect of the task was strongly emphasized to the subjects and they were encouraged to associate the task with some realistic life situation. Thus, for example, a subject might imagine himself in a forest, listening to faint bird sounds.

It was hypothesized that the subjects' eager and expectant concentration on the next click would activate a PK mechanism such as to make this click come in earlier than expected by pure chance.

At the beginning of each session the sound volume was individually adjusted so that the subject could hear approximately 80% of randomly presented clicks. Then 20 runs were made with a break of typically 10 minutes after 10 runs. Some minor psychological differences in the test situation for the pilot test, the confirmatory study, and the test with time displacement are discussed in the following.

The pilot experiment. After some preliminary, informal tests a pilot study was begun in December, 1973, at the Institute for Parapsychology. This study consisted of 20 sessions with 20 different subjects who were members of the laboratory and visitors who expressed interest in this particular experiment.

During a test session the subject, fitted with headphones, was seated in a comfortable chair and was encouraged to relax. No attempt was made to shield the room against external noise. For each test run the experimenter gave a signal to the subject and then started the random generator. When the run ended the weak click was presented to the subject and the advancing display counter in front of the experimenter stopped.

In this pilot test the experimenter was more personally involved than in the later tests in two respects:
1. At the end of each run the experimenter manually recorded the counter reading.
2. The experimenter gave a start signal to the subject at the beginning of each run, and a stop signal in the cases where the subject had not noticed the click at the end of the run. Thus the experimenter had to check the display counter occasionally to see whether the run was still in progress.

For the discussion of the results let us call each decision made by the random generator a "trial." Then in a run the generator makes a certain number R. of consecutive trials until a hit (p = 1/64) is obtained and the run ends. Thus each run contains one hit in a varying number R of trials which is given by the display counter.

For the pilot study 20 different subjects contributed 20 runs each so that the total number of hits (H = 400) was pre-specified, rather than the total number N of trials. Nevertheless, it is easily seen that we can still derive the statistical significance of the result in the usual manner from CR = (H - Np)/((Npq)^(1/2)). The results given in Table 1 (Column 1) indicate that the average run length was significantly reduced from the chance expectancy of 64 to the observed value of 54.23. At the trial rate of 10 per second, this implies that the average waiting time for the next click was reduced from 6.40 to 5.42 seconds.

Table 1


Conventional PKTest with Pre-Recorded Targets
I: PilotII: Conf.III: Test RunsIV: Controls
Number of Subjects203030---
Number of Trials N21693332053381937864
Number of Hits H400600600600
Average Run Length N/H54.2355.3456.3763.08
t (19 or 29 df)3.293.623.66.50
P (one-tailed).001.001.001n.s.
Note. The chance hit probability is p = 1/64 and the average run length, the average number of trials required to obtain a hit, is 1/p = 64.00.

In addition to the CR value for a group of subjects, Table 1 also gives the t-values based on the contributions of the individual subjects. Both these values, CR and t, provide valid measures for the existence of some PK effect in the group. If, furthermore, the contributions of the group members were independent, we could draw from the t-value further conclusions about the distribution of PK abilities over the population, and this would permit statistical predictions about the outcome of later similar experiments.

This requirement of independence, however, need not be satisfied in psi tests because a subject's psi performance does not (like his height or weight) depend exclusively on the subject, but is co-determined by other systematic factors, for example, the mood of the experimenter. Thus, if some of the subjects are tested while the experimenter is in a "good" mood and the others while the experimenter is in a "bad" mood, there may be a systematic difference between the two sub-groups, violating the assumption of subject independence. Therefore we must be cautious if we want to derive from a t-value anything more than the operation of some psi effect.

Extensive randomness tests carried out between experimental sessions verified the value 64 for the chance expectancy of the run length when no PK effort was applied (4000 such runs gave an average run length of 64.48, which is consistent with the assumption of the ideal operation of the random generator). Thus the abnormal scoring in the test sessions appears to be a PK effect. One might want to interpret this effect tentatively in the sense that the subjects in their eager concentration on the next click had subconsciously activated a PK mechanism to make this click come in earlier than expected by chance. But there are certainly other possible interpretations: the subjects might have directed their PK effort such as to please the experimenter (i.e., to confirm his expectation), or the experimenter might have activated his own PK mechanism for this purpose.

Table 2


Conventional PK Test with Pre-Recorded Targets
Interval for RAssociated ProbabilityI: Pilot II: Conf.III: Test RunsIV: controls
Note. The five intervals are chosen so that the associated chance probabilities for a run length R to fall into any one interval are approximately equal. The table gives the observed number of events in each interval.

The trend toward a reduction of the average run length in the experiment is also reflected in the data of Table 2 (Column I). There we have divided the R-axis into five intervals which should by chance contain approximately equal numbers of events. The increased number of events in the intervals corresponding to shorter runs is seen. The interval 1 <=R<=14, for example, contains 98 events (chance expectancy 79.2), whereas the interval 103<=R < infinity contains only 59 events (chance expectancy 80.2). This difference alone is significant (CR = 3.16).

The confirmatory experiment. After the completion of the pilot study a confirmatory test was begun and finished in January, 1974. The pre-specified number of 30 subjects contributed one session each. The subjects were visitors to the laboratory who had expressed interest in the particular experiment.

In an attempt to reduce experimenter involvement, the equipment was changed so that the recording of the data and the start of the runs were done automatically. On the other hand, the experimenter did not reduce his personal efforts to bring the subjects into a highly motivated state.

Let us review the successive experimental steps: First, the subject was psychologically prepared, seated with headphones in a comfortable chair, and the click volume was individually adjusted as in the pilot test. The only remaining task for the experimenter was the pushing of a button to initiate an automatic sequence of 10 test runs. When the button was pushed, a signal lamp was turned off to let the subject know that a run had started and that he should listen for the next click. When the run ended, the weak click was presented and a few seconds later the signal lamp was turned on so that the subject could notice the end of the run even if he had missed the click. At this time the counter reading (giving the length of the run) was automatically recorded on paper punch tape for later computer evaluation. (In addition, the experimenter also recorded the counter readings manually so that he could tell the subject his score immediately after a session.) Ten seconds later the next run was automatically initiated and this was indicated to the subject by the turn-off of the signal lamp. After 10 runs the automatic test cycle stopped, and a break of typically 10 minutes was taken. Then the next 10 trials were completed in the same manner.

Randomness tests at the completion of the sessions, as in the pilot study, were consistent with the theoretically expected average run length of 64.

Table 1 (Column II) shows that in this confirmatory study the average run length in the test sessions was again significantly reduced, from 64 to 55.34 steps, i.e., the average waiting time for the next click was reduced from 6.40 to 5.53 seconds.

Table 2 (Column II) gives the shift in the distribution of the run lengths toward smaller values.

The PK Test with Pre-Recorded Targets In the previous test a random sequence of hits (p = 1/64) and misses (q = 63/64) was produced by the random generator during the test session. The subjects concentrated on the hits (represented by weak clicks) and thereby appeared to exert a PK effect because the hits were generated with increased frequency. In the following test the random sequence of hits and misses which appeared in a test session with a subject was not generated during this session, but was obtained by a replay of a sequence that was generated and recorded earlier (in the absence of both subject and experimenter). This previously recorded sequence had been left untouched, i.e., nobody looked at the sequence until it was played back in the test session.

For the purpose of a comparison between "test runs" and "control runs" only half of the prerecorded sequences was used as the target in a test session. The other half was merely evaluated by a computer and thus not exposed to a subject's attention during a test session.

Let us list the individual steps of the experiment in their proper time sequence: First the random generator (with p = 1/64) was automatically activated (at the rate of 10 per second) in the absence of subject and experimenter. The hits and misses were recorded as signals in the left and right channels respectively on a stereo cassette recorder. After each hit (at the end of each "run"), the number generation was interrupted for 10 seconds. During this time the number of trials made since the previous hit (i.e., the length of the run) was recorded on paper punch tape. Thus we Gave two independent records of the generator output: the magnetic tape and the paper punch tape.

A first sequence of 60 runs generated in this manner was labeled A, and a second such sequence was labeled B. One of these two sequences, A or B, was to serve as target in test sessions and the other as a control. A total of 10 such pairs of 60-run sequences was used for the experiment.

It was decided in advance to use A or B as the target sequence if the last digit of the square root of n as given by a 12-digit desk calculator was even or odd, with n = 2 for the first (A, B) pair, and n = 3, 5, 7 ... (successive primes) for the following nine (A, B) pairs used in the experiment. Although this decision was predetermined, the experimenter became aware of it only after the target generation when he calculated the square root of n.

After the first pair (A, B) of 60 runs was recorded, the first subject was selected. The test sessions were held under the same conditions as those in the previous confirmatory test. The only difference was that the targets came from the prerecorded magnetic tape rather than from a momentarily operating random generator.

After three subjects had been tested in this manner, a second pair of 60 runs was recorded, the target tape (A or B) was determined by calculating the square root of n with n = 3, the next three subjects were tested, and so forth. The results of the experiment were computer evaluated from the paper tape records. These records were found to be in agreement with the manual records of the counter readings during the test sessions.

Table 1 (Columns III and IV) gives the main results. It is seen that the test runs showed a significantly reduced run length (average 56.37), whereas the control runs showed no significant deviation from the chance expectancy value of 64 for the run length. Note that the test and control runs were generated under the same conditions, while the experimenter was unaware of which runs would serve as test or control.

Table 2 (Columns III and IV) confirms these findings: the distribution of the run lengths in the test runs is shifted toward shorter runs whereas the control runs show no abnormality in their distribution.

A comparison between Columns II and III in Tables 1 and 2 suggests that the two arrangements produced very similar PK effects: for the PK effect it did not matter whether the targets were momentarily generated during the session or whether they were obtained by the replay of a previously recorded random sequence.


This experiment is a modification of a previously reported conventional PK experiment (Schmidt, 1973) in which a fast binary random generator produced a sequence of "heads" and "tails" at the rate of either 30 or 300 per second while the subject tried to enforce an increased generation of heads. The subject received momentary feedback on his performance in either of two ways. In part of the experiment the heads and tails were displayed as clicks in the right or left ear respectively, and in the other part the deflection of a display needle from the center position indicated the momentary scoring rate. The PK success rate appeared to be rather independent of the type of display, but significantly dependent on the trial generation speed. With p = 1/2, the average scoring rate at 30 trials per second was 51.6% whereas the scoring rate at the generation speed of 300 per second was only 50.4%.

The main difference in the experiment to be reported now is that part of the targets were not generated during the session, but came from a prerecorded sequence, so that the PK effect on prerecorded targets could be further studied. In this experiment, however, an attempt was made to explore more than the mere existence of PK with prerecorded targets, in the following three respects:
1. During the test runs, trials with momentarily generated targets and with prerecorded targets were alternated in order to make possible a more direct comparison between conventional PK and PK on pre-recorded targets.
2. The pre-recorded targets were generated and recorded at the high speed of 300 per second, whereas the replay in the test sessions occurred at the low speed of 10 per second. This arrangement should test the prediction of a theoretical model (Schmidt, 1975) that the outcome of the experiment would not depend on the method of target preparation, so that in particular the high speed at the prerecording of the targets should not reduce the size of the PK effect.
3. In the first experiment described above the scores obtained with and without time displacement were of the same magnitude. One might try to increase the scores under time displacement conditions, however, by playing the recorded sequence back to the subject not just once, but several times. Thus the subject would spend more effort on each individual event, i.e., each hit would lead to several rewarding success stimuli. The theoretical model suggests specifically that N repeated attempts at the same target should add linearly (for small effects), leading to an N-fold increase in the average deviation from the chance level provided the subject is not aware that the same target is offered several times. If the subject knew this, his attitude toward the task could change because he might consider a second PK attempt at a previously presented target as useless. In the present experiment each prerecorded target was presented four times to the subject, but in different sections of a run, and embedded between momentarily generated targets, so that he was not likely to notice the repeated appearance of some targets.

During a test run the subject received feedback on the binary events, at the rate of 10 per second, in two ways:
1. The deflection (to the right or left) of a display needle was proportional to the scoring rate (heads minus tails)/(heads plus tails) averaged over the last 20 trials. Thus the momentary position of the needle gave the average scoring rate during the preceding two seconds. The subject's task was to move the randomly fluctuating needle mentally as far and as long as possible to the left, corresponding to an increased generation rate of tails.
2. Coupled to the display needle was a variable frequency sound generator so that deflection of the needle to the right or left was accompanied by an increase or decrease of the frequency. The subject listened to the sound through headphones. His task was equivalent to lowering the average frequency of the sound.

Both types of feedback were given simultaneously, but some of the subjects may have concentrated more on one form or the other, and even closed their eyes in order to concentrate better on the sound.

These test conditions seemed psychologically sufficiently similar to those in the earlier experiment so that the experimenter felt confident in beginning the new experiment without a further pilot study.

The Structure of the Test Run The repeated presentation of the prerecorded targets and the mixing with the momentarily generated targets was done as follows:
At the beginning of a test run, while the experimenter was talking with the subject, a sequence of 128 binary random numbers was generated at the rate of 300 per second and stored in a memory (TTL solid state memory 74200, built into a 128-bit circular shift register). For the purposes of permanent record, the number of heads and tails in the sequence was automatically printed on paper punch tape. At this stage neither the experimenter or the subject had any knowledge about the generated sequence, and the subject did not even know that a target sequence had been prepared.

Next, a sequence of 256 binary events was presented to the subject at the rate of 10 per second, with the auditory plus visual feedback described above. The 128 even-numbered events in this sequence were provided directly by the triggering of a binary random generator, but the 128 odd-numbered events came from the sequence stored in the memory. Thus the subject received a mixture of prerecorded and momentarily generated targets.

During a subsequent intermission of about 15 seconds the subject looked at display counters for the total score (number of heads and tails) in this part of the run, and the score was automatically printed on paper punch tape. Then another sequence of 256 binary events was presented, based on the same memory content. Thus the sequence of odd-numbered events was the same as before, but the momentarily generated even-numbered events were new.

This procedure was repeated two more times so that the outcome of the run was determined by 512 momentarily generated targets and 128 prerecorded and four times presented targets.

At the end of the run the memory content was automatically read and the corresponding number of heads and tails was again printed on paper punch tape. In this manner it could be verified that the content of the memory had not changed during the session.

In order to verify the randomness of the generator (this randomness had been computer-tested extensively in the past), five control runs were made before, and five control runs after each test session. In each control run a sequence of 128 binary numbers was generated and recorded in the memory, then the contents of the memory read and recorded. Thus the numbers for the control runs were generated and recorded in the memory under the same conditions as the corresponding numbers serving as prerecorded targets in the PK tests. The 200 control runs did not show a bias (12,715 heads and 12,885 tails, CR = 1.1). As an additional precaution against a constant generator bias, the target side of the generator outputs was alternated after each test session.

The Test Subjects

The experiment was performed at the Mind Science Foundation in San Antonio during the spring of 1975. Twenty subjects were selected from a group of 30 volunteers who had responded to a newspaper advertisement or had contacted the laboratory independently. The volunteers had the opportunity to try out several precognition and PK test devices and when they expressed interest in the experiment now being reported they were either tested immediately or asked to return on another day. Each subject contributed two runs of the type described. The two runs were carried out in one session, but separated by a 15-minute intermission.


Table 3


Momentarily Generated TargetsPre-Recorded and Four Times Presented Targets
Number of Trials204805120
Scoring Rate50.81552.95
t (19 df)1.833.97
P (one-tailed).05.0005
The main results are given in Table 3. We are primarily interested in three quantities: (a) the scoring rate on the momentarily generated targets, (b) the scoring rate on the prerecorded and four times presented targets, and (c) the difference between these two scoring rates.

The average scoring rate of 50.815% on the 20,480 momentarily generated targets is marginally significant. A t-test with the subject as the unit (19 df) or the evaluation of the CR value leads to a (one-tailed) significance level of .05. The scoring rate is lower, but not to a statistically significant degree, than the scoring rate of 51.6% obtained in a previously reported experiment (Schmidt, 1973) carried out under similar conditions.

A higher scoring rate of 52.95% was obtained on the 5120 prerecorded and four times presented targets. From the resulting CR = 4.22 or t = 3.97 (19 df, we obtain a significance level of .0005 (one-tailed).

In order to test whether the scoring rate of 52.95% for the pre-recorded targets is significantly higher than the scoring rate of 50.815% on the momentarily generated targets, we compared for each of the 20 subjects his scoring rate on the prerecorded targets with his scoring rate on the momentarily generated targets. A t-test for the difference between the two means gives t = 2.39 (19 df), which is significant at the .025 level (one-tailed).

Thus our second experiment confirmed the existence of PK with prerecorded targets. Furthermore, the data support the hypothesis that repeated feedback of the prerecorded data can increase the scoring rate. A high scoring rate of nearly 53% on the prerecorded targets was obtained in spite of the fact that they were recorded at high speeds which had previously (Schmidt, 1973) led to much lower scoring rates. This may bias us toward the view that what matters for the outcome of the test is not the physical-psychological conditions at the time of the target generation, but rather the conditions at the time of replay during the test session.


In this experiment the action of PK on two random generators with hit probabilitites of 1/8 and 7/8 was compared. In order to present the targets from these two generators in a psychologically balanced manner, the generators were activated during the test session in random sequence so that the subject never knew whether the next target would be produced by one or the other generator. The hits and misses were presented (in the first part of the experiment) as clicks offered to the subject's left or right ear, no matter from which generator they originated.

So far this may appear to be a conventional PK test since the random generators were activated during the test session. The random order in which the two generators were activated in the test run, however, was determined by a prerecorded sequence of 64 "heads" and "tails." The sequence was produced by a binary random generator with p = q = 1/2 prior to the overt PK test. This sequence was played back during the test run so that each recorded head or tail triggered the generation of one target by the "easy" generator (with p = 7/8) or the "difficult" generator (with p = 1/8). Thus a greater number of heads in the sequence was favorable for a high total score, and therefore the subject's motivation to succeed might affect the outcome of the prerecording. In an attempt to increase such a possible PK effect on the prerecorded sequence, each sequence was used in the test run four times in succession so that each head or tail caused four triggerings of the easy or the difficult random generator.

With regard to the theoretical model (Schmidt, 1975) mentioned above, this experiment appears interesting because the model predicts relationships among the scoring rates on the "easy" trials, the "difficult" trials, and the prerecorded targets.

The Test Equipment

Fig.4 belongs here

Fig.4. Block diagram for the setup in the third experiment.
During a test run a timer (see Figure 4) produced a sequence of 256 pulses at the rate of 10 per second. Each of these pulses triggered an unsymmetric binary random generator so that a signal appeared at the left or right output channel of the generator with the probabilities of 7/8 and 1/8 respectively.

Which of these outputs was presented to the subject, and counted as a hit, depended on the position of an electronic switch which is indicated in Figure 4 by a mechanical double-pole double-throw switch. If this switch is in its left position (as drawn in the figure), a hit is produced by a signal from the left generator output and we have an "easy" trial with the chance hit probability of 7/8. For the other switch positions the hits come from the right channel with a chance expectancy of 1/8 and we have a "difficult" trial.

Three counter pairs registered the total number of hits and misses, and also the hits and misses for the easy and difficult trials separately. This redundant counting seemed desirable in this experiment because the results were recorded only manually. The recording of all six counters provided a safeguard against hidden recording errors.

Next, let us discuss the mechanism which set the electronic switch and thereby determined whether a trial was an easy or a difficult one. Prior to the overt PK test and while the experimenter was talking with the subject, a binary symmetric random generator (with p = q = 1/2) was activated at the rate of 300 per second to produce a sequence of 64 binary events. This sequence was stored in a 64-bit circular shift register (built from the same elements as the memory in the second experiment, described above).

During the test run, with each timer pulse the next event in the shift register was read and, depending on whether it was a "head" or a "tail," the selector switch for the easy and difficult trials was set to the left or right position. In the 256 trials of the run the circular shift register was read through four times. Thus a head or tail in the shift register produced four easy or difficult trials respectively so that an increased number of heads in the prerecorded sequence was favorable for success in the test.

The Subjects and the Test Arrangement

The experiment was performed during the fall of 1975 at the Mind Science Foundation in San Antonio. The subjects were volunteers from among visitors to the laboratory. The pilot test comprised 10 sessions with 10 different subjects. In the confirmatory study a total of 40 sessions was carried out with 28 different subjects. Some of the subjects were permitted to take part in more than one session (up to three sessions) because of a shortage of volunteers. This seemed unobjectionable because we were interested primarily in the existence of an effect and relative scoring rates under different physical conditions, but not in the question of how uniformly these effects are distributed over a given subject population.

Each session involved four of the described test runs, separated by short intermissions. During the intermissions the subject saw his total score and the experimenter recorded the readings of all six counters. Furthermore, the sequence of 64 random events which determined the easy and the difficult trials in the next run was automatically generated and stored in the shift register.

In the pilot test and for the first 20 sessions of the confirmatory study, feedback was given in the form of clicks to the left ear (hits) or right ear (misses). In the last 20 sessions the hits and misses were presented as low-pitched and high-pitched tones respectively.


One objective of the experiment was the comparison of PK scores on "easy" trials, with a hit probability of 7/8, and "difficult" trials, with a hit probability of only 1/8. These two types of trials were offered in random sequence so that the subject was not consciously aware of whether an easy or difficult trial was in progress.

Table 4


Pre-Recorded TargetsEasy TrialsDifficult Trials
N_eN_dCRthetat H_eM_eCRtheta_etH_dM_dCRtheta_dt
Pilot Test134112192.411.10 3.1 (9 df)47006640.271.01 0.3 (9 df)5804296-1.280.95 1.4 (9 df)
Confirmation Session 1-20260625141.291.04 0.6 (11df)90641360-1.690.95 1.3 (11 df)134587112.651.08 1.6 (11 df)
Confirmation Session 21-40261725031.591.05 1.2 (15df)91561312-0.101.00 0.0 (15 df)12458767-0.200.99 0.3 (15 df)
Confirmation Total522350172.031.04 1.3 (27df)182202672-1.260.97 0.8 (27 df)2590174781.741.04 1.0 (27 df)
Note: N_e, N_d, number of "heads" and "tails" in the prerecorded sequences (p=q=1/2) Each head or tall generates four "easy" or four "difficult" trials, respectively, in the test runs. H_e, M_e, hits and misses on the easy trials (p hit = 7/8); H_d, M_d, hits and misses on the difficult trials (p hit = 1/8).

Table 4 gives the main results for the pilot test and the confirmatory study. The results for the first and second half of the confirmatory study are given individually because slightly different types of feedback were used. In the first half the hits and misses were displayed as clicks to the left and right ear respectively, whereas in the second half the hits and misses appeared as low-pitched and high-pitched tones.

As measure of the strength of the PK effect, the corresponding theta-values (Schmidt, 1975) are given. These are defined as

theta_e=H_e/7M_e theta_d=7H_d/M_d


H_e,M_e: hits and misses in the easy trials

H_d,M_d: hits and misses in the difficult trials

Note that the definition of theta is always such that theta = 1 for chance scoring and theta > 1 for a positive PK effect.

The theoretical model (Schmidt, 1975) predicts that, under somewhat idealized conditions (stable and similar performance of all subjects), the two theta-values should be equal, theta_e=theta_d, for a sufficiently long and statistically significant experiment. Unfortunately the CRs in Table 4 indicate that the results are not statistically significant so that the observettheta-value cannot be considered close to the "real" theta-values. Therefore the results neither confirm nor falsify the prediction of the model.

The other objective of the experiment was a study of the hypothesis that PK should also affect the prerecorded sequences of heads and tails which determined the order of easy and difficult trials in the test run. It was expected that an excess of heads (hits) should occur because each head produced four easy trials, and an above-chance number of heads was thus highly advantageous for the subject.

Table 4 gives the total numbers N_e for heads (producing easy trials) and N_d for tails (producing difficult trials). The corresponding theta-value is defined as

theta' = N_e / N_d.

The pilot test seems to support the hypothesis of a PK effect. There are more heads than tails in the sequences, with a significance level of .01 (CR = 2.41, and considering the 10 individual sessions, t = 3.1 with 9 df).

The effect in the confirmatory study is reduced, however, and only marginally significant at the .05 level (CR = 2.03, t = 1.3 with 27 df). Thus we have some indication of the existence of a PK effect on the prerecorded targets, but the results are too weak to draw any more detailed conclusions. In particular, we cannot check the prediction of the theoretical model that the repeated use (four times) of the prerecorded targets should, for a sufficiently long and significant experiment, lead to an increased theta-value, i.e., theta' = 4 theta_e = 4 theta_d.

One more analysis was made: Considering the values for theta_e, theta_d, theta' in the 40 sessions of the confirmatory study, the correlation coefficients between these measures were determined. None of these correlations were statistically significant.


The reported work indicates that PK effects can be obtained in tests with prerecorded targets. The results suggest slightly more than the mere existence of such effects. The following points appear particularly interesting in this respect:
1. Whereas the main experiments reported above were conducted by one experimenter (the present writer), significant results in pilot tests were also obtained by two other experimenters. Particularly high PK scores on prerecorded targets resulted from a test by Dr. E. F. Kelly with Mr. Bill Delmore as subject, who had performed outstandingly in tests with several investigators. Thus it seems to be the subject rather than the experimenter who is the PK source, and the effect does not appear to be restricted to one experimenter.
2. In the first experiment conventional PK tests and corresponding tests with prerecorded targets gave similar results, suggesting that the same basic PK mechanism was operating in both situations.
3. In the first experiment test runs and control runs were prerecorded under the same conditions so that not even the experimenter knew the difference. Nevertheless, only the test recordings (which were presented as targets in a test session) showed anomalous scores. This suggests that the subject's effort at the playback session was instrumental for the PK effect.
4. In the second experiment the prerecorded targets were generated at a very high speed which had in earlier tests (Schmidt, 1973) led to a low scoring rate (50.4%). Nevertheless this experiment, in which the targets were played back four times at the low rate of 10 per second, produced a much higher scoring rate (52.95%). This again seems to favor the hypothesis that what matters for the result is not the conditions at the time of target generation, but those at the time when the targets are presented to the subject in the test session.
5. In the second experiment the scoring rate on the prerecorded and four times presented targets was significantly higher than the scoring rate on the targets which were momentarily generated and presented only once in a session. Thus it appears that repeated replay of the prerecorded target sequence to one subject (or perhaps to several different subjects) can lead to an increase in scoring rate.
6. In one of the pilot tests described above, the subject, Mr. Lalsingh Harribance, made his PK efforts when he was alone at home, while he received immediate feedback from a tape recorder. (The experiment was adequately safeguarded since the prerecorded targets to be used in the evaluation of the results never left the laboratory; only a transcribed copy went out to the subject.) In this manner it appears possible to channel PK effects into the laboratory from a subject who is completely free to hold the test session wherever and whenever he wants.
With any interpretation of the results one has, of course, to be cautious for several reasons. First, one might want to postpone serious discussion until we have more detailed experimental information from several independent experimenters. Second, the failure of the third experiment to give more than a marginally significant PK effect reminds us that we may still be overlooking some vital factors which have a stronger effect on the test results than the variables we are studying. And finally, a meaningful interpretation in this area of research, far outside our intuitively accessible everyday experience, can be made only with reference to some theoretical model: we have to devise logically consistent psi models and then see which of these models agrees best with the experimental results.

One detailed model (Schmidt, 1975) and some more rudimentary models on the operation of PK on prerecorded targets have been mentioned above in the introduction. The detailed model seems consistent with the findings, and in particular with the addition effect in the second experiment.

On the other hand, the observed addition effect might also be explained in terms of the quantum theoretical model in the sense that the first presentation of the targets, at the rate of 10 per second, did not bring all the targets to the conscious awareness of the subject, so that repeated presentation could improve the results. Further experiments which compare repeated feedback and simple feedback at very slow rates might be able to distinguish between the two models, but at present we cannot expect any of the few available models to be more than an incentive for further experimentation.


DEWITT, B. S. Resource letter IQM-1 on the interpretation of quantum mechanics. American Journal of Physics, 1971, 39, 724-738.
SCHMIDT, H. PK tests with a high-speed random number generator. Journal of Parapsychology, 1973, 37, 105-118.
SCHMIDT, H. Comparison of PK action on two different random number generators. Journal of Parapsychology, 1974, 38, 47-55.
SCHMIDT, H. Toward a mathematical theory of psi. Journal of the American Society for Psychical Research, 1975, 69, 301-319.
SCHMIDT, H., AND PANTAS, L. Psi tests with internally different machines. Journal of Parapsychology, 1972, 36, 222-232.
STANFORD, R. G. An experimentally testable model for spontaneous psi events. II. Psychokinetic events. Journal of the American Society for Psychical Research, 1974, 68, 321-356.

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