Academic journal article The Journal of Parapsychology

Effect of a Threatening Subliminal Stimulus on the Perceptual ESP Test: A Partial Replication

Academic journal article The Journal of Parapsychology

Effect of a Threatening Subliminal Stimulus on the Perceptual ESP Test: A Partial Replication

Article excerpt

When I was working in the Netherlands, Martin Johnson and I conducted an elaborate experiment that used a perceptually based ESP test (Palmer & Johnson, 1991) inspired by a procedure of Barbara Lovitts (1981). A slide with a quasi-random assortment of the lowercase letters a-d was flashed to subjects for 150 ms, and they were asked to respond with the letter that seemed most salient to them when the slide flashed. This was probably, but not necessarily, the letter that was in the center of the visual field. The idea was that a paranormal process would guide the subject's eye movements in such a way that the fixated or otherwise most salient letter would match a randomly selected target letter being viewed by an agent. The broader purpose of the procedure was to minimize the often intellectual kind of mental activity associated with more traditional ESP tests in which subjects are required to conjure up an image or impression. There are indications in the literature that such thought processes are psi-inhibiting, especially in forced-choice ESP tests (Stanford, 1975).

Immediately prior to the presentation of the letter slide, a subliminal picture

was flashed to the subject. The picture was either the standard Defense Mechanism Test (DMT) slide (Kragh & Smith, 1970) in which a threatening male figure is peering down at a boy seated at a desk, or a control slide in which the countenance of the male figure in the background is pleasant and smiling. We expected more negative ESP scores when the face was threatening than when it was smiling. The hypothesis was not confirmed, but two post hoc findings suggested to us that there might have been some ESP in the data. First, there was overall tight variance, which means that the scores clustered more closely around mean chance expectation (MCE) than one would expect by chance. Tight variance has been associated with a negative mood in the literature (Rogers, 1966, 1967). The puzzling aspect of this finding was that the tight variance was present with the smiling subliminal picture as well as the threatening one. We offered two possible explanations. First, the smiling picture may not have been as benign as we originally thought; for example, we thought in retrospect that it could be construed as lecherous, especially by females. Second, we thought that a possibly negative context of the experiment as a whole could have caused the tight variance. For instance, to fulfill the requirements of a visual field manipulation, subjects had to wear uncomfortable goggles and place their chin on a chin rest during the ESP task.

Second, there was a confirmation of Stanford's (1975) response-bias hypothesis. In cases where a particular letter was called six times or less out of the 40 trials, the number of hits on these undercalled trials was significantly above chance and significantly greater than on the remaining trials.

Because one purpose of the perceptual ESP test is to minimize linear thought processes, I had hoped that there would be less evidence of response biases with this procedure than with a traditional forced-choice ESP test. It seemed that such biases were indeed reduced, particularly the undercalling of XX doublets, but the biases were still present to some degree.

The present experiment is a partial replication of the Palmer and Johnson experiment. The intent was to reproduce the situation in which scoring on the perceptual ESP test can be influenced by the immediately prior subliminal presentation of a threatening stimulus, the standard DMT slide. It was also intended to make the test situation more pleasant for subjects than it was in the Palmer and Johnson experiment, primarily by eliminating the visual field manipulation. Also, the sample was restricted to persons genuinely interested in the research; most subjects in the earlier study participated to receive course credits in a psychology class. Thus, one alternative explanation of the tight variance effect found by Palmer and Johnson was removed. …

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