It is suggested that the rotating spiral and its after-effect may be used as a method of inducing and measuring reactive inhibition, or some perceptual parallel. Several related experiments are reported outlining the effects of massed and spaced practice and the reminiscence phenomenon resulting from the dissipation of inhibition, usually by rest. Stimulant and depressant drugs are shown to change the rate at which inhibition is generated, and also dissipated, in a predictable fashion. Another experiment outlines the way in which reactive inhibition generated by massed practice can be dissipated by an external stimulus. It is suggested that the occasional failure to generate reactive inhibition may be due to spontaneous dissipation by extraneous external or internal stimuli.