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The bulk of this volume consists of 27 research papers that were originally published during the years 1943 to 1960 in a variety of medical and psychological journals. Unfortunately, most of these studies lack necessary controls. To draw definitive conclusions concerning the phenomena of hypnosis, it is necessary to assign subjects from a homogeneous population at random to experimental and control groups and to treat both groups in the same way with the controls. With a few possible exceptions, the studies reprinted in this volume failed to meet these requirements for controlled research in at least one of two ways:
1. A number of experimenters failed to randomize assignment of subjects to experimental and control treatments. Salzberg, for instance, selected his hypnotic group, but not his control group, from subjects meeting criteria for high suggestibility. He found that suggestions for enhanced learning proficiency were effective with the hypnotic subjects but
Barber TX. Clinical Correlations of Experimental Hypnosis.. Arch Gen Psychiatry. 1964;10(5):544. doi:10.1001/archpsyc.1964.01720230106013