EFFECTS OF STIMULUS-DURATION AND INTENSITY ON SIMPLE REACTION-TIME AND RESPONSE FORCE

Previous research indicates that response force increases with stimulu s intensity in simple reaction time (SRT) tasks. This result contradic ts the common view that the perceptual system activates the motor syst em via a punctate go signal of fixed size. An elaborated view assumes that the size of the go signal depends on stimulus intensity so that m ore intense stimuli yield more forceful responses. In order to examine the latter hypothesis, the present experiments manipulated stimulus d uration as well as intensity. Response force increased with duration e ven beyond a critical value of about 60 ms at which stimulus duration no longer affected SRT. In addition, increasing the duration of a stim ulus also increased the duration of force output. These findings argue against models with punctate transmission of activation to the motor system. Certain continuous models and variable output models with prol onged go signals provide acceptable accounts of these effects.