Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 at noncognitive levels of awareness and be measurable, even though not expressed verbally. Tt was assumed that the application of remote stimuli would result in responses similar to those obtained under conditions of direct stimu- lation. 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 the brain waves at the frequency of the flashes. We hypothesized that if we stimulated one subject in this manner (a sender), the EEG of another subject in a remote room with no flash present, (a receiver), might show changes in alpha (9-11 Hz) activity, or possibly LEG driving similar to that of the sender. Applying this concept, 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 perceived that event, consciously or unconsciously, it might be evident from changes in his EEG output. The receiver was seated in the visually opaque, acoustically and electrically shielded double-walled steel room previously described. The sender was seated in a room across the hall from the EEG chamber at a distance of about 7 meters from the receiver. In order to find subjects who were responsive to such a remote stimulus, we initially worked with four female and two male volunteer subjects, all of whom believed that success in the experimental situation might be possible. These were designated “receivers.'"' The senders were either other subjects or the experimenters. We decided beforehand to run one or two sessions of 36 trials each with each subject in this selection procedure, and to do a more extensive study with any subject Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0
Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 whose results were positive. A Crass PS-2 photostimulator placed about 1 meter in front of the sender was used to present flash trains of 10 sec duration. The receiver's EEG activity from the occipital region (07), referenced to linked mastoids, was amplified with a Grass 5P-1 preamplifier and associated driver amplifier with a bandpass of 1 to 120 Hz. The BEG data were recorded on magnetic tape with an Ampex SP 300 recorder. On each trial, a tone burst of fixed frequency was presented to both sender and receiver, and was followed in one second by either a ten-second train of flashes or a null flash interval presented to the sender. Thirty- six such trials were given in an experimental session, consisting of 12 null trials--i.e., no flashes following the tone--12 trials of flashes at 6 fps, and 12 trials of flashes at 16 fps, all randomly intermixed. Each of the trials generated an ll-second EEG epoch. The last 4 seconds of the epoch was selected for analysis to minimize the desynchronizing action of the warning cue. This 4-second 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. However, of the six subjects studied initially, one subject (H.H.) showed a consistent alpha blocking effect. We therefore undertook further study with this subject. Data from 7 sets of 36 trials each were collected from this subject on three separate days. This comprises all the data collected to date with this subject under the test conditions described above. The alpha 20 Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0
Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 band was identified from average spectra, then scores of average power and peak power were obtained from individual trials and subjected to statistical analysis. Of our six subjects, H.H. had by far the most monochromatic EEC spectrum. Figure 3 shows an overlay of the three averaged spectra from one of this subject's 36-trial runs, displaying changes in her alpha activity for the three stimulus conditions. Mean values for the average power and peak power for each of the seven experimental sets were given in Table 3. The power measures were less in the 16 fps case than in the 0 fps in all seven peak power measures and in six out of seven average power measures, Siegel's two-tailed t approximation to the nonparametric randomization rest)? was applied to the data from all sets, which included two sessions in which the sender was removed. Average power on trials associated with the occurrence of 16 fps was significantly less than when there were no flashes (t = 2.09, df = 118, p< .04). The second measure, peak ‘power, was also significantly less in the 16 fps conditions than in the null condition (t = 2.16, df = 118, p< .03). The average response in the 6 {ps condition was in the same direction as that associated with 16 fps, but the effect was not statistically significant. Spectrum analyses of control recordings made from saline with 12K ohms resistance in place of the subject with and without the addition of a 10 Hz,.50 uV test signal applied to the saline solution, revealed no indications of flash frequencies, nor perturbations of the 10 Hz signal. These controls suggest that the results were not due to system artifacts. 21 Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0
Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 arbitrary units VOLTAGE e s ° 5 Hz 10 Hz 15 Hz THREE CASES — 0, 6 and 16 Hz flashes (12 trial averages) FIGURE 3 OCCIPITAL EEG FREQUENCY SPECTRA, 0 TO 20 Hz, OF ONE SUBJECT (H.H.) ACTING AS RECEIVER SHOWING AMPLITUDE CHANGES IN THE 9-11 Hz BAND AS A FUNCTION OF STROBE FREQUENCY Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 22
Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 Average Power Peak Power ll 6 16 a) 6 16 —_—_—_—_~-_~ 4 84.1 76.8 | 357.7 329.2 289.6 rf] u : . 45.5 37.0 | 160.7 161.0 125.0 {l ll No Sender H (Subject informed) . 35.7 28.2 H 87.5 95.7 81.7 | il 55.3 44.8 l 191.4 170.5 149.3 u 50.9 32.8 I 240.6 178.0 104.6 i 24.9 30.3 l 145.2 74.2 122.1 {I No Sender i (Subject not . 53.0 52.1 {| 318.1 180.6 202.3 informed) tl veces ts ne i __ ge Averages . 49.9 43.1 " 214.5 169.8 153.5 -12% -24% (P<.04) ~21% -28% (P<.03) TABLE 3. EEG data for H.H. showing average power and peak power in the 9 - 11 Hz band, as a function of flash frequency and sender. Each table entry is an average over 12 trials. 23 Approved For Release 2003/04/18 : ClIA-RDP96-00791R000200040003-0
Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 Further tests also gave no evidence of radio frequency energy associated with the stimulus. Subjects were asked to indicate their conscious assessment for each trial as to which stimulus was generated. They made their guesses known to the experimenter via one-way telegraphic communication. An analysis of these guesses has shown them to be at chance, indicating the absence of any supraliminal cueing. Thus, we note that in this pilot study, one of six subjects showed significant EEG changes associated with the presence of remote stimuli under conditions of sensory shielding. This form of noncognitive arousal evidenced by alpha blocking has also been observed by Tart (1963), using a small electric shock stimulus applied to himself as sender in a similar experiment.’ We hypothesize that the protocol described here may prove to be useful as a screening procedure for latent remote perceptual ability in the general population. DISCUSSION We have presented evidence for the existence of a biological informa- tion channel whose characteristics appear to fall outside the range of known perceptual modalities. The precise nature of the channel or channels is as yet undefined, but may involve either direct perception of hidden information content, perception of mental images of persons ‘knowledgeable of target information, precognition, or some combination of these or other information channels. 24 Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0
Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 We have worked with three individuals, two of whom are reported on in detail here, whose remote perceptual abilities were sufficiently developed that they were able to describe both pictorial and geographical material blocked from ordinary perception. In addition to experiments which centered on subjects' conscious perceptions, we have also conducted EEG experiments in which we have found statistically significant evidence of direct physiological indications of nonconscious perception of remote stimuli. The observation that a nonconscious link with physiological correlates can exist between separated individuals is one that merits considerable study. From these experiments we conclude that | ° A channel exists whereby information about a remote location can be obtained by means of an as yet unidentified perceptual modality. ° As with all biological systems, the information channel appears to be imperfect, containing noise along with the signal. 0 While a quantitative signal-to-noise ratio in the information- theoretical sense cannot as yet be determined, the results of our experiments indicate that the functioning is at the level of useful information transfer. It may be that remote perceptual ability is widely distributed in the general population, but because the perception is generally below an individual's level of awareness, it is repressed or not noticed. For example, two of our subjects (H.H. and P.P.) had not considered themselves to have unusual perceptual ability before their participation in these 25 Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0
Approved For Release 2003/04/18 : CIA-RDP96-00791 R000200040003-0 experiments. We conjecture that it is partially the prevailing philosophical attitudes of the times in which we live that prevent such ability as may exist from surfacing to a greater extent. Our shared cultural constraints deny permission for the demonstration of such abilities. With regard to the methodology itself, our observation of the phenom- ena leads us to conclude that experiments in the area of so-called paranormal phenomena can be scientifically conducted. The results presented here offer a basis from which departures as a function of other observables can be studied. Our goal for future experimentation is the investigation of the physical and psychological laws underlying these phenomena, rather than just the addition of further demonstrations of the statistical appearance of paranormal phenomena-in the laboratory. ACKNOWLEDGMENTS © This research was sponsored by The Foundation for Parasensory Investi- gation, New York City. We wish to thank its president, Mrs. Judith Skutch, and their representative, Dr. Edgar D. Mitchell of the Institute of Noetic Sciences--as well as our SRI associates, Mr. Bonnar Cox, Mr. Earle Jones, and Dr. Dean Brown--for their support and encouragement throughout this work. We also wish to acknowledge Dr. Wilbur Franklin of Kent State Uni- versity for his contribution, especially in the early phases of this research. Finally, we acknowledge the many constructive suggestions provided us through conversations with Mrs. Jean Mayo, Dr. Charles Tart, University of California, and Dr. Robert Ornstein and Dr. David Galin of the Langley Porter Neuropsychiatric Institute. 26 Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0
Ww 10. Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 REFERENCES J. Pratt, J.B. Rhine, C. Stuart and J. Greenwood, EXTRA SENSORY PERCEPTION AFTER SIXTY YEARS, New York, Henry Holt, 1940. S. Soal and F. Bateman, MODERN EXPERIMENTS IN TELEPATHY, London, Faber and Faber, 1954. » L.L. Vasilliev, EXPERIMENTS IN MENTAL SUGGESTION, Hampshire, England, ISMI Publications, 1963. - J.R. Musso and M. Granero, "An ESP Drawing Experiment With a High- Scoring Subject," J. of Parapsychology, Vol. 37, pp. 13-37, March, 1973. It has been widely reported that Mr. Geller has demonstrated the ability to bend metal by paranormal means. Although metal bending by Mr. Geller has been observed in our laboratory, we have not been able to combine such observations with adequately controlled experiments to obtain data sufficient to support the paranormal hypothesis. K. Osis, ASPR Newsletter, No..14, Summer, 1972. C.T. Tart, PHYSIOLOGICAL CORRELATES OF PST COGNITION, Intl. J. of Parapsychology, Vol. V, No. 4, Autumn, 1963. E.D. Dean, "Plethysmograph Recordings as ESP Responses," Intl. J. of Neuropsychiatry, Vol. 2, October, 1966. D. Hill and G. Parr, ELECTROENCEPHALOGRAPHY : A SYMPOSIUM ON ITS VARIOUS ASPECTS, Macmillan, New York, 1963. 5. Siegel, NONPARAMETRIC STATISTICS FOR THE BEHAVIORAL SCIENCES, Pp. 152-156, New York, McGraw-Hill Book Co., Inc., 1956. 27 Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0
Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 APPENDIX Following is the unedited transcript of remote viewing Experiment 7, where the target was an Arts and Crafts Garden Plaza. This is a large plaza resembling a California mission, There are craft shops around the perimeter of the plaza, In the plaza area are many gardens, flowers, ceramic pots, fountains, and paths. Overhead are vines on arbors of redwood. Price's description is accurate in almost every detail and he omitted little of importance, 1:40 THIS IS A REMOTE VIEWING EXPERIMENT WITH PAT PRICE, DEAN BROWN, AND RUSSELL TARG IN THE SHIELDED ROOM IN BUILDING 30. THE TRAVELLERS TO REMOTE LOCATION ARE BART COX, HAL PUTHOFF, JUDY SCHMICKLEY AND PHYLLIS COLE, WE EXPECT THE TRAVELLERS TO BE AT THEIR PLACE IN ABOUT 10 MINUTES, IT'S 1:58, OUR TRAVELLERS SHOULD BE NEAR TO ARRIVING AT THE PLACE, OK, Why don't I start scanning by quadrant using this as a center point. 12-3, 6-9....., I'll go from 12-3 first. Seems to me right now that I'm picking them up in the 12-3 quadrant, but I'll g0 on in the rest and look. JI haven't actually identified them, I just feel that they're there, Nope, I don't get them there, Now I'll go from 6-9. While I was looking at 6-9, it looks to me like T'm looking at an iris, a flower of some kind, I'll come back and identify that later. Just wanted to get it down as having a flash of an iris flower-purplish. I'11l continue to scan that quadrant. Nope, don't get them there, I'll go from 9-12, Don't get them there, I'll go back 12-3, Yeah, I get them in that quadrant, Now I'll see if I can locate them physically and identify the area, I'm looking at something that looks like an arbor, trellis-work arbor. Seems to be cool, shaded. Doesn't seem to me that they're out in the direct sunlight. Be more like there's lots of trees, in an arbor area. 1 Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0
Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 The arbor appears to be made of wood, possibly redwood. They're just....looks like it's a dirt path, quite wide, I'd say maybe 12 ficet. _iI can see some grass, Looks like possibly a fountain of some kind, Yeah, I can see Bart in his red shirt and what looks like kind of a gray paisley tie - I didn't really look at that when he was down there, The red shirt, I did. Looks like he has on a gray paisley tie. It appears they're walking along quite leisurely. Looks like there's some red brick laid into a walkway. They don't seem to be on it, they just seem to pass over that. I got - it seems like a little ways away from them there are quite a few people but right where they're walking it doesn't appear to be many right in there, This is an arbor area, Back of that arbor, back here I'd say 50 feet from that arbor to here, seems to be a lot of people in here, They were walking along here on what looks like about a 12 foot dirt path, WHAT KIND OF PLACE IS THE ARBOR IN? IS IT A FIELD OUT IN THE OPEN? No, I want to say park, but it doesn't exactly feel like a park. If you took a - the feeling I'm getting - it's not the specific place - but like the Town and Country Market. That type of an atmosphere, with quite a section of it into a little outdoor park, but basically I'm getting a very strong feeling of flowers. Like the first one I saw was an iris. TELL ME ABOUT THE TOWN AND COUNTRY ASPECT, IN WHAT WAY DOES IT REMIND YOU OF TOWN AND COUNTRY, The buildings, not right where they're at, but very close to them have that same kind of architecture and look. The parking lot looks similar, grand, sweeping, not cluttered, it's more expansive area. You take a place like Sears Mall - it seems cluttered. This seems more leisurely paced, People are moving about slower - there's not the hustle and bustle - more or less meandering, Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0
Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 TOWN AND.COUNTRY MEANS TO ME A COVERED WALKWAY, Yeah, the back of them it seems to be - where they are seems to be a very large arbor like vines growing over it and things, and there possi- bly - I haven't looked in there yet to see if there's any displays like pottery and things - I get the feeling that there is right close to it. ALSO, OUTDOORS? Yeah, it seems like fairly high shade trees - kinda bordering. The center part doesn't seem.to have it - this part in here. The trees seem to be way up in here along like this over here. This seems to be shaded in here, but it's sunny out here, I just saw something that looked like a windmill - not a farm type wind- mill ~ a Dutch-type windmill. It's smaller - it's not a huge thing, but I'm getting a definite feeling that it's like a windmill. The area in there feels damp - not wet - they're not walking in water, but it's very moist. The temperature in there...it's secluded, Feels very comfortable. A little on the shady side. WHAT DO YOU FIND AS THE BOUNDARIES OF THE PLACE THEY'RE AT? Outside of this little park-like affair. that they seem to be in, there's a street. One side of it seems to be a kind of a residential...the other seems to be a little bit more heavily travelled. Let me pick up a little bit more, I can see one very large oak tree - exceptionally large. Right now Bart is trying to point something out that is basically the Significance of the whole place. It's like that key thing, well, if you'd have mentioned a salt pile I'd have blown my lid, Well, this has a significance that's just about comparable to that. -I'm screening it out. Thing that just flashed in was kind of like a stadium structure - like looking down into a stadium. Just when I did that I - I'll have to reorient to make sure I'm looking in the same area now, Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0
‘ _— Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 Seoms Like they're - I still get them in the same quadrant I had them in originally. 5Scems like some decorative brick walls. THE QUADRANT YOU HAD THEM IN IS BASICALLY THE NORTHEAST QUADRANT? Yeah, I got them out about this far - it's not far away - I'd say in this direction over here about - feels like a mile to a mile and a half, They don't feel as far away, and I'm not looking at the time continuum, They actually don't feel as far away. I'd say that it is about - not half the distance they were to the marina, and it seems to be on a line just about in that direction but just a hair more - rather than a direct line from here to the marina - they seem to be just Slightly more to the left of that line, I was looking back to where he had the car parked and it seems like it's on asphalt -then a curb in front, and then it's like a dirt walkway and then a sidewalk. But I can see eucalyptus buds on the ground and some branches of eucalyptus there. One of the most dominant things to me in the way of unusualness is the size of the oak tree that I'm looking at. Looks like an arboretum, or I get the definite feeling of flowers. Almost get the feeling like it's commercial flowers. In fact, the most predominant feeling that I'm getting right now is flowers. Don't know why iris particularly. There's something about the windmill that I was going to look at. Wasn't that what you were,,..? Be like one you'd almost see in a miniature golfcourse...the windmill. Has all the construction and detail but not as large - it's fairly small. Seems to be made out of dark redwood and it's kind of aged, I'm going to try to look more directly to them. Let's see, there's Bart and Hal, and behind Bart is Judy and behind Hal is Phyllis, kinda stag- gered there, Looks like a possible small pool of water - like a garden pond. Looks like a little bridge. Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0
Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 I was trying to get the feeling of what type of an area it was. Let me elevate a bit. I'm looking at much too small an area. There's some greater significance there that I feel I'm definitely not looking at - let's jack up a bit...maybe 500 feet. I see a lot of trees, I see Judy's red hair and her brown eyes and her flashing teeth - she has beautiful teeth. Hadn't really looked at them before. Phyllis and her are talking about something and Hal and Bart are talking about something and he's pointing at something and it seems to me that he's pointing over to what I'd call a windmill or something that Looks Like a windmill. The water I see looks more like a pool or a pond than it does - you know, it's not big like a lake - not very large, but it looks like a definite pool, Right where they're at I don't hear too much traffic noise - it seems to be fairly quiet. Looks like a little wooden walkway. Feels a little early, but it kinda seems like they're retracing their steps heading back toward the car, but they're still moving quite leisurely. IF YOU LOOK DOWN ON THE PLACE FROM ABOVE, CAN YOU GET ANY FEELING FOR THE - IS THERE ANY OVERALL LAYOUT OR PLAN? When i went up I could see trees and stuff, and I kind of got the feeling of like in a corner of a golf course, you know - where there would be a lot of trees overhanging the green and some things in there - that seemed to be out of context, but when I elevated, that's what I got. It kind of looked like an overlap to me, so I didn't talk about it, but I will. When I elevated it kind of felt like it was right over the corner of a golf course of some kind, with a street running down one side, and they are fairly close to that, In fact, the bricked area that I looked at or like a patio thing kinda looks like a walkway. Seems like there's small building - small meaning not tall - looks like a single story building. Looks like it has a flat roof - slightly pitched. Looks like 4 x 4 poles supporting it - has a Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0
Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 canopy out over it. They're painted white, place looks like very possible light yellow or cream color, They're walking not too far from that. Still seems to me that they're on a dirt pathway. In the area that they're in now I get flowers again - where before they kinda fell out of the flowers, Looks like’ maybe 80-100 yards from where they are ~ looks like 2 guys on a motor scooter. They can see them, WHAT WOULD YOU SAY IS THE INTEREST TO THIS PLACE? WHAT'S SPECIAL ABOUT THIS PLACE? It seems to be a kind of a recreational, relaxed..,not energetic - looks more relaxed. I'd say it's kind of combination recreational and relaxation area that I'm getting out of it. That would be the general character of it. Two aspects - one is aesthetics and the other is a kind of a mild recre- ational area. There seem to be some unique features - I don't have it totally into context as yet. There's a number of things that I've rejected ~- looked at and rejected saying, First, I got the impression that it was kind of like a miniature golf course - I rejected that. Merely from saying it - I didn't reject the principle - I just rejected saying it. Then I kind of got the idea of a standard golf course - I also rejected that on the same principle, so I'm just trying to describe the terrain. Seems expansive - doesn't seem cluttered, Just got a flash of something that reminded me of the gyroscope - gimbals on the gyroscope. Drinking fountain - looks like it's made out of kinda like field stone built up into a fountain...bowl, I'm going to elevate again and go through a search quadrant again. Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0
Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 I still get them in that general location, so that seems to set all right. Distance - maybe a mile, mile and a half. Doesn't seem much farther- seems fairly close, The area has an awful lot of grass, lot of trees - looks like dirt walk- ways, well trimmed. I can see the arbor, and the arbor could be a place to sit and be out of the direct-sun. May be a few little tables and benches and chairs in there, That outlooks over quite a grassy area - there are quite a few trees. I see basically an oak, Right after they got out of the car I could see some eucalyptus buds and branches on the ground, and it seemed like the trees were there, Looked like they got out of the car, stepped upen a curb, dirt parkway, a sidewalk, and then they went into this area. [ get the feeling this windmill type thing - that all seems fairly real. The feeling is still that it's relaxing and has some recreational aspects - I just haven't put it totally together as to giving it a name, Right now I get a very strong impression of flowers again. It seems like right now they're back to right where I originally spotted them only they're going in the opposite direction - like they're moving toward the direction they Originally went. While they were there they walked on several pathways - walked out quite a ways, then swung over and come over and worked around and looked at... One peculiar thing I might note - so far I haven't sensed, seen nor heard an airplane. Cars seem quite distant - outside of that little motor scooter affair with the two guys on it. That's about the only vehicular traffic I've seen - except out in the parking lot. It seems like to me that they've got most of their attention off what they were looking at and they've got their attention more on the car now, Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 .
ec iaerae Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 T want to look and find out what the significant thing was that Bart was talking about. There's something quite unusual there and I .., Damned if I can pick it up, WAS HAL DOING ANYTHING BESIDES WALKING ALONG - WAS THERE ANY ACTIVITY FOR HAL TO DO? Most of the time I was looking at Hal,he was kind of listening to Bart and Bart was pointing out a number of things, Part of the time Bart was walking with Hal; part of the time he was back by Judy. When I first saw them, it was Bart in the front on the left side, Hal was on his right, Judy was Slightly behind - almost between Bart and Nal but behind, and Phyllis to her right, They wandered around but the first time I picked up - they were that way, When they were coming back, they just about reversed, Bart would be in front. When they were coming back, it looked like Bart was in front with Phyllis, and Judy was walking more behind Bart and Hal on her right When they were coming back out of there, They're actually at the car. 2:30 SHALL WE GO DOWNSTAIRS AND SEE HOW THEY'RE DOING? Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0
CPYRGHT . Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 “« Perception & Psychophysics 1973, Vol. 14, No. 2, 313-318 dig) IE A study of sine-wave contrast sensitivity by two psychophysical methods* D. H. KELLY and R. E. SAVOIE Stanford Research Institute, Menlo Park, California 94025 In the literature on visual contrast thresholds for sine wave gratings, little attention has been paid to the psychophysical methods used to. obtain these spatial-frequency response curves. Here we report a comparison of such data obtained by two quite different psychophysical methods, but otherwise under identical conditions, using five Ss. Both experiments were run by computer: (1) In the method of adjustments, the computer program merely controls the order of the stimuli and records S’s contrast settings. (2) In the forced-choice staircase (FCS) technique, the program determines how often § can discriminate the sinusoidal grating from a uniform field, informs S$ of his accuracy. controls the stimulus contrast on-the basis of S’s preceding responses, and brackets his threshold by a series of successive approximations. ‘Method 2. eliminates criterion effects that occur in Method 1, and hence tends to minimize individual differences.‘ However, the FCS technique requires. an -order of magnitude more observing time to obtain equally smooth contrast sensitivity curves. FCS also increases the overall sensitivity of some Ss by as much as five times, but it does not significantly.change the shape of the contrast sensitivity curve; both methods show strong effects of lateral inhibition at low spatial frequencies. Measurements. of the contrast threshold fora sinusoidal grating as a function of its. spatial frequency have been used to study the effects on the visual process of optical, neural, chromatic, temporal, and other factors. Van Meeteren (1966) has reviewed a number of these stydies. We. are particularly interested in the low-frequency region of such data, below about 2 oycles/deg (cpd), because the monotonic increase of contrast sensitivity with increasing spatial frequency in this region tay represent a simple form of lateral inhibition (Kelly, 1973). | In certain cases, little or no low-frequency falloff was reported (e.g., Westheimer, 1960; Campbell. & Green, 1965), but this has-been attributed to the use of small, sharp-edged targets (Davidson, 1966; Kelly, 1970) or flash, presentations. (Kelly, 1971, 1973), which are unsuitable for isolating the steady-state response to very “low spatial frequencies. However, some Ss report’ that ‘the task of detecting a low-frequency grating seems difterent from the high-frequency detection task; this raises the question of whether the apparent inhibition would persist at low frequencies if criterion effects were eliminated; Many of the data in the literature have been obtained by the psychophysical method of adjustments, which is the easiest and fastest procedure when Ss are experienced in-this type of judgment: variations of the method of limits have also been used. But more sophisticated psychophysical methods have been developed in recent years which are essentially independent of threshold criterion: these have not been *Our work was partly supported by NIH Grant No, NS-08322 and NSF Grant No. GB-11571. Some of the data were reported at the October 1971 meeting of the Optical Society of America in Ottawa, Canada, We thank T. N. Cornsweet for suggesting this study. . applied to. the measurement of sine wave contra ihresholds. We therefore undertook to compare the sine wave thresholds obtained by the method of adjustments with those obtained by a forced-choice staircase (FCS) paradigm, in which the S was always informed of the correctness of his choice. Our main purpose was to find out whether the low-frequency inhibition was independent of criterion effects, but our results are also relevant to other sine wave.contrast experiments that use subjective judgments. METHODS The stimulating apparatus is described’ in detail elsewhere (Kelly, 1966, 1972); its components are shown schematically in Fig. 1. S is seated comfortably, viewing a cathode ray tube (CRT) 50 em distant through an artificial. pupil, 2.3. mm in diam. He sees an 8-deg circular field, filled by. 4 vertical sinusoidal grating: ‘The. spatial frequency of. this grating is controlled .by a (LINC 8) computer. The dependent variable . is, the Michélson contrast (m) of the grating. defined as * Bmax ~ Bmin. m —— * Bmax + Brain’ where, Bmax and Bin are the maximum and minimum values of the stimulus waveform. in trolands (td) of retinal illuminance. This contrast is under the control of either the computer or the S, depending on the mode of operation. Since the grating does not flash or flicker in the present experiments. our temporal waveform source was.not used (sce Fig, 1). Adjustments Mode In the method of adjustments, the S controls the contrast of the grating, using a geared-down potentiometer without stops or other mechanical cues. Spinning the’“knob about 1,200 deg covers the entire adjustment range. which may be either 0-1 or 0-0.1 contrast, depending on a switch controlled by the S. Another switch gives him the option of viewing zero or full contrast at any time, without losing his potentiometer setting. When the setting mects his threshold criterion, he pushes a Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0
Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 . CPYRGHT 314 KELLY AND SAVOIE —— SCAVNING HORIZONTAL ) ke? VERTICAL | Me SPATIAL cOUNGTER PATTERN = 4 | | sounce —i— (SOURCE | Le i ft cavstat CLOCK, | [ai guppy CONTRAST f— | artenuaton PEDESTAL (x) METHOD OF ADJUSTMENT [BLANKING AND SYNC TEMPORAL SAMPLE WAVEFQRM AND HOLD ——_ i MARKER TUNE CHOICE SCANNING HORIZONTAL 1 aH VERTICAL 1 Mie SPATIAL PATTERN source | cavstat ciock, | Ta spy BLANKING ANDO SYNC] |" —" CONTRAST i FADING , LINC .B | COMPUTER CONTRAST LALTENUATOR PEQESTAL . CvCee no th) FOACED-CHOICE STAIRCASE METHOD Fig. 1. Signal-flow diagrams of the CRT | stimulator. (a) Configuration for method of adjustments. (b) Configuration for forced-choice staircase (FCS) procedure. button which enters this contrast into the computer. He is instructed to fixate the center of the grating and to find the contrast at which it can just be discriminated from a uniform field. (This criterion, which we always use for sine wave thresholds, should come close-to matching S’s performance in the forced-choice task described below.) S spends as much time as he wishes “hunting” back and forth to find his threshold, but we instruct him to make his final judgments only in the steady state; ie.. after he has refrained from changing the contrast for several seconds. Twelve spatial frequencies were tested in one experimental session; each pattern was presented five times in random order, for a total of 60 judgments. The means of these five settings gave fairly smooth spatial-frequency response curves, as described below. An experienced S can complete such arun in 20-25 min. Forced-Choice Staircase (FCS) Mode Our criterionless psychophysical procedure combined the staircase method of ordering stimuli (Békésy, 1947; Cornsweet, 1962) with the forced-choice method of response collection (Blackwell, 1946; Heinemann, 1961). In this application, the two techniques complement each other in such a way that $ spends most of his time making discriminations near threshold. The S’s task is much simpler in the FCS mode. The same 12 stimulus patterns are used, but their contrast is now under the control of the computer. One stimulus cycle consists of two successive intervals, each 5 sec long; a pattern of nonzero contrast is presented in only one of these intervals, which is determined by the computer from a table of random numbers. One second after the beginning of cach interval. a marker tone sounds to notify $ that the stimulus may be visible. He makes his choice of interval by pushing a button, which also starts the nent trial; but this button has no effect until after the second tone. In other words, S must make a choice in order to start a new trial. but he cannot do so until after the second interval has started. As soon as he makes his choice, he hears a pleasant tone (different from the marker tone) if he is correct or an unpleasant noise if he is not. His only other control is a “‘pause” switch, which interrupts the experiment for rest periods. S may use this switch also to abort a given trial (if, for example, he happened to be looking away when the marker tone sounded). The aborted trial is repeated when the pause switch is reset, but the stimulus will not necessarily occur in the same interval. In order to avoid transient effects (Kelly. 1971, 1973), as we do in the adjustments mode, the temporal waveform of the FCS stimulus is carefully controlled. The mean luminance of the CRT screen is held constant throughout the experiment. When a given pattern is presented, its contrast is smoothly “faded in” from zero to whatever value is set by the computer, as shown in Fig. 2a. The temporal envelope of the fade-in waveform resembles a half-cycle of a 0.5-Hz cosine wave, so that the full contrast of the pattern is present after 1 sec (this contrast always being zero in either the first or second interval, at random), The pattern is also faded out the same way. All 12 staircases are independent and randomly interleaved, which helps to eliminate subjective bias effects (Cornsweet, 1962). On each trial, the contrast of the FCS stimulus is contingent on the correctness of the preceding responses to the same pattern, according to an algorithm described in detail in the Appendix. When the responses indicate that S can detect the pattern, the contrast is decreased, when he cannot, the contrast is increased, by a constant logarithmic increment in either case. Thus, the contrast is forced to cross and recross the threshold level (which is about 75% correct). At first, the size of the increment is decreased each time the response sequence indicates that a contrast increase has probably crossed $’s threshold. But the third time this indication occurs, the smallest increment (30% contrast change) is maintained and the staircase is terminated with a fixed number of additional trials. A typical staircase illustrating these properties is shown in Fig. 2b. Each stimulus is first presented at full contrast, to familiarize $ with its appearance and to provide a suprathreshold baseline. If he detects it correctly, its next presentation is at a contrast of 0.02; the staircase then enters the main algorithm (see Appendix). INCREMENT Si7E ox ma en Farst Interval CONTRAST CONTRAST Thresher ut AON ‘ wy Me 1 5 10 16 20. TIME -- seconds TRIAL NUMBER Marker Tones Occur al the Arraw “m" is Controtied by the Contest Alganthen Stimulus Occurs in the First or Second Interval at Rendam fa) FORCED-CHOICE PRESENTATION CYCLE tht TYPICAL STAIRCASE Fig. 2. Details of the FCS procedure. (a) Temporal waveform of one stimulus cycle and timing of alerting tones. (b) A single . staircase, reassembled to show all contrasts presented, increment sizes, wrong responses, and calculated threshold. Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0
Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0 CPYRGHT Several hundred trials are required to terminate all 12 staircases; an experimental session usually takes 65-75 min, gardiess of the skill or experience of the S. Most of the hriability in length of the individual staircases (Rose et al, 1970) if averaged out by the large number of staircases being run multaneously.2 The threshold for each pattern is calculated as the mean of the Ifst eight contrasts presented, no adjacent pair of these being geparated by more than the smallest increment. The intersession ariability of FCS data obtained in this way is no greater than in fhe adjustment mode, but is mainly random rather than gystematic. Thus, to obtain equally smooth spatial-frequency sponse curves, one must average the data from three FCS gssions, as described below. RESULTS Figure 3. shows some contrast sensitivity data bbtained with a 20-year-old emmetropic naive S. The hpper curve (filled circles) represents combined data rom three FCS runs; three comparable adjustment urves are plotted separately (open circles). These data re typical of our results in three ways. First, the shape hf the FCS curve is essentially the same as that of the hdjustment curves; in both cases, the contrast sensitivity Increases steeply at low spatial frequencies, to a aximum near 4cpd. Second, the FCS sensitivity is ystematically greater than that in any of the adjustment Tuns, by a factor of 2.to 5. Third, there are also bystematic differences among the individual. adjustment urves, but these are smaller than the FCS-adjustment Hifferences. The lowest sensitivity in Fig.3 represents the first Se aN | “ —_—o CONTRAST 4 / oe FCS Adjustments = ist Run -—- 2nd Run —- 3rd Run 0.5 1 2 5 10 SPATIAL FREQUENCY (cpd) 0.2 Fig. 3. Contrast sensitivity vs spatial frequency for S K.S. Retinal illuminance, 1,300 td; artificial pupil, 2. mm. Filled circles are the means of three FCS runs. Open circles represent three successive adjustment runs. SINE-WAVE CONTRAST SENSITIVITY 315 Subj. GK CONTRAST —o— FCS 0.2 I —o-—~ Adjustments 4 1 l { I —1 0.2 0.8 1 2 “5 10 SPATIAL FREQUENCY (cpd) Fig. 4.. Contrast sensitivity vs spatial frequency for S D.K. Same conditions as Fig. 3. experiment with SK.S.. Her .adjustment sensitivity increased subsequently, but leveled off between the second and third adjustment runs. Typically, a naive S starts with a high threshold criterion, which he then lowers after some experience with the method of adjustments. However, his adjustment thresholds seldom get as low as his FCS thresholds: apparently he adopts a criterion in the range of 90%-100% probability of detection (compared to the 75% imposed by the FCS mode). : Figure 4 shows a similar comparison for another S. S DK. (one of the authors) is somewhat atypical, having had hundreds of hours of practice in experiments with this particular “apparatus. If practice lowers the adjustment threshold, his adjustment sensitivity should be gtéater than that of SK.S.; and it is, relative to his FCS sensitivity. His adjustment sensitivity may still. be slightly: less than his FCS sensitivity, but the two are much closer togéther than they are for our other Ss. Evidently -he uses a lower threshold criterion, closer to the FCS level. As in Fig. 3, the FCS curve in Fig. 4 was obtained by averaging data from three sessions, a total of about 3.5 h observing time. , However, the contrast sensitivity curves obtained from individual FCS sessions are also instructive: these are shown for a third S in Fig.5. Each of the dashed curves in this figure-connects the end points of the 12 staircases obtained in a single experimental session (see Fig. 2b). The mean curve for these three FCS sessions is shown for comparison with the previous figures. Figure 5 also shows some systematic variation among three adjustment runs for this S. (SH.P. was more experienced than K.S., but even an experienced S will not always hold the same adjustment criterion from one run to the next.) Again; the FCS sensitivity is about five Approved For Release 2003/04/18 : CIA-RDP96-00791R000200040003-0