POSSIBLE EEG CORRELATES TO REMOTE STIMULI UNDER CONDITIONS OF SENSORY SHIELDING

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• Publication Date: April 19, 1977
• Content Type: RP

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Electro/77
Special Session
The State of the Art in
Psychic Research
14" Electro77 Professional Program
New York, April 1921, 1977
Copyrights 1977 Electro
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POSSIBLE EEG CORRELATES TO REMOTE STIMULI UNDER
CONDITIONS OF SENSORY SHIELDING
E. C. May,* Russell Targ, and H. E. Puthoff
Stanford Research Institute, Menlo Park, California 94025
ABSTRACT
We have investigated the ability of certain
individuals to perceive remote (faint) stimuli
at a noncognitive level of awareness. To inves-
tigate this we have looked for systematic
changes in a subject's brainwave (EEG) produc-
tion occurring at the same time as light flashes
are generated on a random schedule in a remote
laboratory. Although we have found in this in-
vestigation that significant correlations appear
to exist between the times of light flashes and
the times of brainwave alterations, we consider
these data to be only suggestive, with a defini-
tive result requiring further experimentation.
INTRODUCTION
In a number of laboratories evidence has
been obtained indicating the existence of an as-
yet-unidentified channel wherein information is
coupled from remote electromagnetic stimuli to
the human nervous system as indicated by physio-
logical response, even though overt responses
such as verbalizations or key presses provide no
evidence for such information transfer. Physio-
logical measures have includes plethysmographic
responsel and EEG activity. 219 Kamiya, Lindsley,
Pribram, Silverman, Walter, and others have
suggested that a whole range of EEG responses
such as evoked potentials (EPs), spontaneous
EEG, and the contingent negative variation (CNV)
might be sensitive indicators of the detection
of remote stimuli not mediated by usual sensory
processes.4
A pilot study was therefore undertaken at
SRI to determine whether EEG activity could be
used as a reliable indicator of information
transmission between an isolated subject and a
remote stimulus. Following earlier work of
others, we assumed that perception could be in-
dicated by such a measure even in the absence of
verbal or other overt indicators.
To aid in selecting a stimulus, we noted
that Silverman and Buchsbaum attempted, without
success, to detect EP changes in a subject in
response to a single stroboscopirg flash stimu-
lus observed by another subject. Kamiya sug-
gested that because of the unknown temporal
characteristics of the information channel, it
might be more appropriate to use repetitive
bursts of light to increase the probability of
detecting information transfer.6 Therefore,
*Consultant to SRI.
in our study we chose to use repetitive light
bursts as stimuli .-9
PILOT STUDY AT SRI
In the design of the study it was assumed
that the application of remote stimuli would
result in responses similar to those obtained
under conditions of direct stimulation. For
example, when normal subjects are stimulated
with a flashing light, their EEG typically shows
a decrease in the amplitude of the resting
rhythm and a driving of tbs brain waves at the
frequency of the flashes. We hypothesized that
if we stimulated one subject in this manner (a
putative sender), the EEG of another subject in
a remote room with no flash present (a receiver),
might show changes in alpha (8-13 Hz) activity,
and possibly EEG driving similar to that of the
sender, either by means of coupling to the sen-
der's EEG, or by coupling directly to the
stimulus.
We informed our subject that at certain
times a light was to be flashed in a sender's
eyes in a distant room, and if the subject per-
ceived that event, consciously or unconsciously,
it might be evident from changes in his EEG out-
put. The receiver was seated in a visually
opaque, acoustically and electrically shielded
double-walled steel room located approximately
7 m from the sender's room.
We initially worked with four female and
two male volunteer subjects. These were desig-
nated "receivers." The senders were either other
subjects or the experimenters. We decided be-
forehand to run one or two sessions of 36 trials
each with each subject in this selection proce-
dure, and to do a more extensive study with any
subject whose results were positive.
A Grass PS-2 photostimulator placed about
1 m in front of the sender was used to present
flash trains of 10 s duration. The receiver's
EEG activity from the occipital region (Oz),
referenced to linked mastoids, was amplified with
a Grass 5P-1 preamplifier and associated driver
amplifier with a bandpass of 1-120 Hz. The EEG
data were recorded on magnetic tape with an Am-
pex SP 300 recorder.
On each trial, a tone burst of fixed fre-
quency was presented to both sender and receiver
and was followed in one second by either a 10 s
train of flashes or a null flash interval pre-
sented to the sender. Thirty-six such trials
were given in an experimental session, consisting
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of 12 null trails--no flashes following the
tone--12 trials of flashes at 6 f.p.s. and 12
trials of flashes at 16 f.p.s., all randomly in-
termixed, determined by entries from a table of
random numbers. Each of the trials consisted of
an 11-s EEG epoch. The last 4 s of the epoch
were selected for analysis to minimize the desyn-
chronizing action of the warning cue. This 4-s
segment was subjected to Fourier analysis on a
LINC 8 computer.
Spectrum analyses gave no evidence of EEG
driving in any receiver, although in control runs
the receivers did exhibit driving when physically
stimulated with the flashes. But of the six sub-
jects studied initially, one subject showed a
consistent alpha blocking effect. We therefore
undertook further study with this subject. Of
our six subjects, this one had by far the most
monochromatic EEG spectrum. Figure 1 shows a
typical occipital EEG spectrum of this subject.
6 8 10 12 14 16
FREQUENCY - Hz
FIGURE 1 TYPICAL POWER SPECTRUM AVERAGED OVER
TWENTY 8-SECOND EPOCHS
Data from seven sets of 36 trials each were
collected from this subject on three separate
days. This comprised all the data collected to
date with this subject under the test conditions
described above. The alpha band was identified
from average spectra; then scores of average
power and peak power were obtained from indi-
vidual trials and subjected to statistical anal-
ysis. The final analysis showed that power
measures were less in the 16 f.p.s. case than in
the 0 f.p.s. in all seven sets of peak power
measures and in six out of seven average power
measures.
Siegel's two-tailed t approximation to the
nonparametric randomization testil was applied
to the data from all sets, which included two
sessions in which the sender was removed. Aver-
age power on trials associated with the occur-
rence of 16 f.p.s. was significantly less than
when there were no flashes (t = 2.09, d.f = 118,
P < 0.04). The second measure, peak power, was
also significantly less in the 16 f.p.s. condi-
tions than in the null condition (t = 2.16,
d.f. = 118, P < 0.03). The average response in
the 6 f.p.s. condition was in the same direction
as that associated with 16 f.p.s., but the ef-
fect was not statistically significant.
As part of the experimental protocol the
subject was asked to indicate conscious assess-
ment for each trial as to which stimulus was
generated. The guess was registered by the sub-
ject via one-way telegraphic communication. An
analysis of these guesses has shown them to be
at chance, indicating the absence of any supra-
liminal cueing, so arousal as evidenced by sig-
nificant alpha blocking occurred only at the
- noncognitive level of awareness.
Several control procedures were. undertaken
to determine if these results were produced by
system artifacts or by subtle cueing of the
subject. Low level recordings were made from
saline of 12 kO resistance in place of the sub-
ject, with and without the introduction of
10 Hz, 50 ?V signals from a battery-operated
generator. The standard experimental protocol
was adhered to and spectral analysis of the
results were carried out. There was no evidence
in the spectra associated with the flash fre-
quencies, and the 10 Hz signal was not
perturbed.
In another control procedure a five foot
pair of leads was draped across the subject's
chair (subject absent). The leads were con-
nected to a Grass P-5 amplifier via its high
impedance input probe. The bandwidth was set
0.1 Hz to 30 kHz with a minimum gain of 200,000.
The output of the amplifier was connected to
one input of a C.A.T. 400C "averager." Two-
second sweeps, triggered at onset of the tone,
were taken once every 13 seconds for approxi-
mately two hours, for about 550 samples. No
difference in noise level between the fore-
period and the onset of flicker was observed.
REPLICATION STUDIES AT LANGLEY PORTER
The next effort was directed toward repli-
cation by an independent laboratory of the
original SRI study of EEG response to remote
strobelight stimuli. Arrangements for replica-
tion were made with the Langley Porter Neuro-
psychiatric Institute, University of California
Medical Center, San Francisco.
As a special precaution against the possi-
bility of system artifacts in the form of elec-
tromagnetic pickup from the strobelight dis-
charge or associated electronic equipment (e.g.,
through the power lines), SRI developed an
entirely battery-operated package for use as a
stimulus generator for the EEG experimentation.
It consists of a battery-driven incandescent
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HALLWAY
BETWEEN
ROOMS
1 kHz TONE
GENERATOR
2 sec BEFORE
EACH TOTAL
PERIOD (Light,
or No Light)
lamp, whose CW output passes through a mechani-
cal chopper continuously driven by a battery-
driven motor as shown in Figure 2. A 10-Hz
timing generator (computer triggered) controls
the generation of a 1-kHz warning tone two sec
before onset of the experimental period, and
also drives a locking circuit that determines
the presence or absence of the tea-sec light
stimuli, again all battery operated.. Thus
everything on the left of the diagram of Fig-
ure 2 is battery operated and therefore inde-
pendent of the power line system. Further,
replacement of the arc-discharge strobelamp by
an incandescent lamp eliminates the possibility
of direct subliminal pickup of audio or elec-
trical signals from possible transients associ-
ated with the arc discharge or associated
electronics.
Description of the EEG Processor
A hardware single channel power spectrum
analyzer was constructed from a commercial band-
pass filter with corner frequencies of 9.0 and
12.0 Hz, and 48 dB down at 8.0 and 13.0 Hz.
Analog multipliers convert the filter output to
a signal proportional to in-band power. To con-
firm that this system is equivalent to the stan-
dard FFT analysis used in the pilot study, the
analog data of the pilot study was reanalyzed,
and the result was found to be consistent with
the earlier analysis.
Experimental Protocol
Each experimental session consisted of 40
trials, 20 each for the 0 (no light) and 16
f.p.s. of the remote light stimulus. A trial is
defined as a warning tone followed by a 10 sec-
ond period consisting of a 2 second wait, and
two 4 second data collection periods. The trial
rate was one trial every 30 ? 1 seconds. The
trial sequence was randomized subject to the
following conditions: (1) in each group of 10
trials there were equal numbers of each condi-
tion, and (2) no more than three in a row of a
single type were allowed. Seven 40 trial se-
quences were made according to this prescription
and recorded separately on audio tape. During
the session, trials were generated from one of
these tapes and the sequence was unknown to the
experimenters since the sequence tapes were
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generated one month in advance of the experi-
ments. As in standard EEG protocol, and in
accordance with preestablished criteria, certain
trials were deleted after the session for three
reasons only: artifact, logic circuit failure,
or abnormal EEG power. If a trial was rejected,
a trial of the opposite stimulus condition was
rejected at random from the particular set of 10
trials in question. If more than 10 trials of
a given type were rejected from a session, the
entire session was deleted. (This occurred
twice in each experiment.)
Six channels of EEG and one logic channel
taken from the sequence tape were recorded on a
multiplexed FM analog tape recorder. The logic
on the tape differentiated the trials between
flashing and nonflashing conditions.
In pretesting the equipment, we ran the
experiment using unselected subjects such as
laboratory personnel, in order to test the
adequacy of the experiment and to determine
whether there were any correlated electronic or
mechanical discharges from the apparatus. In
20 sessions of data acquisition, of 40 each (800
trials) there were no significant differences
between the null and 16 Hz conditions.
Using the above protocol, two experiments
were conducted during a three-month period. For
half of the sessions, the subject was asked to
press a button when she felt the light was
flashing. For the six sessions (105 trials each
for the 0 and 16 f.p.s. conditions when she was
not asked to overtly indicate her feelings about
the light, there was a slight decrease of in-
band EEG power measured over the left occipital
region of the brain. Similarly, for the six
sessions (107 trials each for the 0 and 16 f.p.s.
conditions) when she was asked to respond overt-
ly, there was this time a significant decrease
of in-band EEG power (p S 0.037, using an F
ratio test derived from a two-way analysis of
variance). In considering the experiment as
consisting of the combined 212 trials in each
stimulus condition regardless of the overt re-
sponse contingency, we find a statistically sig-
nificant decrease in in-band EEG power (p <
0.011, using F ratio test as above).
During the second experiment, three months
later, a different contingency was added to de-
termine if a "sender" was necessary to produce
the effect we had observed earlier. For a given
session, a random procedure (with equal trials)
was used to determine if a person (called the
"sender" person) would be looking at the photo-
simulator. There was no one present with the
photo-stimulator otherwise. For the 7 "non-
sender" sessions (121 trials each for the 0 and
16 f.p.s. conditions) we find a statistically
significant increase of in-band EEG power mea-
sured over the mid-occipital region of the brain
(p < 0.039 using an F ratio test as above).
During the "sender" sessions (123 trials in each
stimulus condition) there was a slight increase
of in-band EEG power. All together, there was a
statistically significant increase of in-band EEG
power when the 244 trials were analyzed regard-
less of "sender" condition (p < 0.008 using an F
ratio test as above), and there was no signifi-
cant difference found between "sender"/"no-
sender" conditions.
For both experiments, we considered in-
band EEG power for the 0-4 second and 4-8 second
time periods independently to determine if the
effects were time dependent. Although some of
these isolated sub-intervals were statistically
significant, no systematic relationship emerged.
Thus the effect appears to be cumulative over
the 8 seconds. The 0-8 second results are sum-
marized in Table 1.
SUMMARY OF RESULTS OF THE REPLICATION EXPERIMENTS SHOWING
POWER MEANS AND STATISTICAL RESULTS FOR THE VARIOUS EXPERIMENTAL CONDITIONS
Experiment I
Experiment II
Guessing
Non-Guessing
Sender
Non-Guessing
Sessions
Sessions
Combined
Sessions
Sessions
Combined
No light flash
957
704
832
854
766
810
Light flash
873
647
761
860
844
852
F ratio
4.39
2.20
6.47
0.017
4.33
7.03
df1; df2
1; 202
1; 198
1; 400
1; 232
1; 228
1; 460
p s
0.037
0.14
0.011
0.90
0.039
0.0083
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DISCUSSIC2 have been found. Thus, although our filter
Although our pilot experiment and the two
replication studies all showed significant
changes in EEG production correlated with the
presence or absence of a remote light stimulus,
the sign of the systematic change in power in
the third study was opposite to that of the
first two. We therefore undertook a detailed
frequency analysis of the EEG data tapes from
the last two experiments, since the pilot ex-
periment had already been subjected to fast-
Fourier-transform (FFT) analysis. We conjec-
tured that the observed power change in these
experiments might be the result of a very small
frequency shift, which could become translated
into a large amplitude change due to discrimi-
nator action of the alpha-band filter. In a
chapter on alpha blocking, Kooi, in his Funda-
mentals of Electroencephalography says, for ex-
ample, ". . attentiveness is associated with a
reduction in amplitude and an increase in aver-
age frequency of spontaneous cerebral poten-
tials. . . The center frequency of the alpha
rhythm may be influenced by the type of ongoing
mental activity. Shifts in frequency may be
highly consistent as two different tasks are
performed alternately." The FFT analysis for
the second experiment showed that the average
peak EEG power occurred most often near 8 Hz,
and thus fell slightly below the hardware sum-
ming window (?3 dB at 8.7-12.4 Hz) enhancing a
possible discriminator effect. The FFT analysis
further showed that there was an overall in-
crease in frequency of peak power but the shift
was statistically nonsignificant. This slight
shift of 0.11 Hz could possibly account for the
observed power increase due to the highly, non-
linear discriminator effects. In examining
other portions of the spectrum for further ef-
fects,, we found that systematic amplitude
changes are highly dependent upon where in the
frequency spectrum the power sum is taken. This
is to be expected since almost all EEG phenomena
are known to be strongly frequency dependent.
In the pilot study the frequency region for
analysis was centered about the subject's domi-
nant EEG output frequency with bandpass deter-
mined by the full width ten-percent power points.
In the two replication studies we used hardware
filters at this same frequency. FFT analysis.
showed clearly that if other filter bands had
been chosen, significant correlations would not
selection was made before the collection of any
data, other experimenters might have reasonably
chosen other criteria for frequency selection.
Therefore, although we have found statistically
significant evidence for EEG correlates to re-
mote light flash stimuli, we consider these data
to be only suggestive, with a definitive result
requiring further experimentation.
REFERENCES
1. E. D. Dean, Int. J. of Neuropsychiatry,
Vol. 2, p. 439, 1966.
2. C. T. Tart, Int. J. of Parapsychology,
Vol. 5, p. 375, 1963.
3. T. D. Duane and T. Behrendt, Science, Vol.
150, p. 367, 1965.
4. R. Cavanna, Ed., Psi Favorable States of
Consciousness. New York: Parapsychology
Foundation, 1970.
5. Ibid., pp. 143-169.
6. Ibid., pp. 158-159.
7. R. Targ and H. Puthoff, "Information Trans-
mission Under Conditions of Sensory Shield-
ing," Nature, Vol. 252, No. 5476, pp. 602-
607, October.18, 1974.
8. C. Rebert and A. Turner, "EEG Spectrum
Analysis Techniques Applied to the Problem
of Psi Phenomena," Physician's Drug Manual,
Vol. 5, Nos. 9-12, Vol. 6, Nos. 1-8,
pp. 82-88, January-December 1974.
9. H. Puthoff and R. Targ, "A Perceptual Chan-
nel for Information Transfer Over Kilometer
Distances: Historical Perspective and
Recent Research," Proc. IEEE, Vol. 64,
No. 3, pp. 329-354, March 1976.
10. D. Hill and G. Parr, Electroencephalo-
graphy: A symposium on its Various
Aspects. New York: MacMillan, 1963.
11. S. Siegel, Nonparametric Statistics for
the Behavior Sciences. New York: McGraw-
Hill, 1956, pp. 152-156.
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