The Prl Autoganzfeld Revisited: Refuting the Sound Leakage Hypothesis

Internal patterns in the PRL autoganzfeld database may shed some light on the plausibility of that hypothesis. This hypothesis would predict stronger effects for sessions where the subject is not sure about his ratings, because in those sessions the experimenter may be able to influence him or her into another direction. A secondary analysis where the scoring in sessions with an extreme rating is compared with the scoring in sessions with a lower rating shows the opposite trend. Therefore it can be concluded that this pattern does not support the auditory sound leakage hypothesis. The PRL autoganzfeld database, which is available for serious independent researchers, is a rich source for secondary analyses. In its original form it consists of 354 records, each describing an individual session in the PRL autoganzfeld series. Each record consists of 80 fields with information like the time, date, set, target, and ratings, but also gender of sender, receiver, and experimenter, and lots of other dependent measures relating to the session, and the participants. In the course of the last few years a number of “calculated” fields have been added. For instance, number of sessions per day was inferred from the time and date information. A number of informal analyses resulted from questions that researchers in the field have asked. The results of these analyses were generally discussed within the context of the electronic discussion group “PDF.” For example, it turns out that the PRL database did not support the often heard supposition that having more than 1 session per day is detrimental for the results. Also, there appears to be suggestive indications for a gender interaction effect where female experimenters with male receivers produce the best results. In this short contribution we will focus on an analysis that was done in order to see if the PRL database showed internal patterns that would support or contradict the sound leakage hypothesis put forward by Wiseman et al. ( Wiseman, R., Smith, M., & Kornbrot, D., 1994). The results of this The Journal of Parapsychology, Vol. 63, Sept 1999 (pp. 271–274) The material in this article was originally presented in a poster session at the Parapsychological Association 43 Annual Convention. analysis were communicated to Wiseman et al. before they published their report, but although they claim that “the likelihood of potential non-psi explanations can also be assessed on the basis of whether they account for internal effects” (p. 450) they did not include these internal pattern figures in their report. The Sound Leakage Hypothesis According to the sound leakage hypothesis, sound cues originating with the sender could have been perceived by the experimenter during an autoganzfeld (AGF) session. The experimenter could have inferred the target from these cues and could subsequently have communicated this information to the “receiver” during the judging phase of the experiment. The authors conclude after an elaborate evaluation of the different acoustic pathways from sender to experimenter that within the actual situation “. . . it would have been almost impossible to consciously detect sender noise. However, some studies concerned with auditory sensory subliminal perception suggest unconscious registration”(p. 449). Thus the experimenter is supposed to have not been explicitly aware of the target and it must be concluded that the influence that the experimenter must have exerted on the subjects’ choice has also been of a similar unconscious nature. Experimenters directly involved in the AGF series have generally considered the sound leakage hypothesis as a ridiculous proposal. This feeling was partly based on the informal qualitative evaluation of the quality of the hits. And, indeed, it is quite difficult to see how unconscious pressure by the experimenter on the receiver during judging would 272 The Journal of Parapsychology Table 1 Scoring Percentage for Sessions with Different Maximum Ratings Maximum Rating N Hits Percentage