A Clock Paradigm to Study the Relationship between Expectancy and Response Force

It has recently been demonstrated that the force used by subjects to press a response key depends on stimulation conditions such as stimulus intensity, foreperiod, etc. We performed an experiment in which response force and reaction time were measured as a function of expectancy. In contrast to the paradigms used so far, we manipulated expectancy without using warning stimuli by applying a so-called “clock-paradigm.” It enabled us to avoid the possible arousing effect of the warning stimulus. Both reaction time and response force depended on expectancy. The results suggest that response force was not affected by arousal or activation but was affected by preparatory state at the moment of making a response.