Drugs and Personality

Abstract

It is a well-known principle in psychology that the effects of sensory stimulation do not cease when the stimulus itself ceases. The so-called visual after-images are probably the best known of these after-effects, but almost equally well known are those induced by a rotating spiral. If a normal person fixates the centre of the rotating spiral for a period of time, and if then the motion of this spiral is suddenly stopped, an after-sensation of movement is well nigh universal. This after-sensation is opposite to the original motion in direction, just as the after-image produced by the fixation of a colour is usually the complementary colour to that which caused the original perception. There is little doubt that while peripheral factors play some part in these after-effects, central features also play a part, and it becomes tempting, therefore, to use phenomena of this type in attempts to verify or disprove the drug action hypotheses advanced by one of us in a previous paper. This hypothesis stated that stimulant drugs increased excitatory potential and decreased inhibitory potential, while depressant drugs decreased excitatory potential and increased inhibitory potential. The question now arises as to how this general postulate can be applied to the phenomena under discussion.