Duration and effects of post-hypnotic suggestions
A pioneer study to measure the length of time the effect of post-hypnotic suggestion lasts, and to describe the curve of its decrease with time and the factors influencing its permanence. The suggestion employed involved a specific variation in the rate of respiration. The subject was instructed that while reading even-numbered pages of a given book, he would breathe at twice the regular rate, and on the odd-numbered pages he would breathe half as fast as usual. These instructions were given to one group of subjects in the trance, and to a control group as simple waking instructions. The 13 Ss were all students, and the readings were from a book of poems containing material frankly boring to the Ss. 6 of the 8 trance Ss remained in complete ignorance throughout the experiment of any change of breathing, nor did they guess that a post-hypnotic suggestion was being tested. The results are computed in the form of ratios of the observed respiratory rates to those indicated in the instructions. Normals showed no loss in the power of the suggestion with time, whereas the opposite was true of the trance subjects. During the first three weeks the trance Ss in general decreased rapidly, while the normals had a tendency to rise at first, attaining at 15 days after the suggestion a mean of 150% of the original ratio. "The power of post-hypnotic suggestion steadily decreases during the first three weeks after it is given. Obedience to waking instructions shows no loss except in accuracy of performance. After the first sharp fall the trance Ss seem to have reached a level where the effect of practice and the decrease in the potency of the suggestion neutralize each other, and on this low level obedience to the suggestion may continue indefinitely." (PsycINFO Database Record (c) 2012 APA, all rights reserved)
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