Experimenter effects in ESP research
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The experimenter effect is considered to be a central problem impeding the progress of research in parapsychology. A review of the literature suggests most if not all the findings of ESP research are experimenter dependent. The evidence for experimenter effects both in psychological and parapsychological research is presented; that in psychology is found to suffer front several methodological and statistical flaws, while that in parapsychology is found to be impressive but largely anecdotal and post-hoc. A critical appraisal is made of the 'interpersonal theory' of experimenter effects. Five possible factors or areas of interaction which may mediate the effect are designated. These are : experimenter expectancy, spontaneous subjective states, experimenter personality, rapport, and experimenter psi. Hie evidence for these mediating factors is presented in detail, along with the hypotheses formulated from it and the research done to evaluate the hypotheses. The research method involved a diverse program of pilot and follow up studies and encompassed the testing of a special high scoring subject by experimenters, group testing methods, questionnaire studies, and experimenter comparison in the use of a sensory input attenuation technique (the Ganzfeld). The results although equivocal in some areas gave little support for four of the factors being as critical as claimed. It was concluded that psychological factors traditionally regarded as conducive to ESP, are probably not necessary and sufficient factors for its occurrence. The fifth factor, that of experimenter psi-mediation, received some support from a study of 'successful' experimenters. The theoretical implications of this are discussed in full along with current process and field models of ESP and some specific suggestions are made for further research in this context.