THE EFFECT OF STIMULUS-INTENSITY ON FORCE OUTPUT IN SIMPLE REACTION-TIME-TASK IN HUMANS

The force needed to press the key in a simple reaction time task was m easured as a function of stimulus intensity for visual and auditory st imuli in three experiments using a total 45 male and female human subj ects. Intensity ranged from 0.316 to 1995 cd/m(2) for visual stimuli a nd from ranged from 47 to 102 dB for auditory stimuli. We found, in ag reement with Angel's (1973) original study, that for auditory stimuli higher intensity is accompanied by a larger force. Surprisingly, in th e case of visual stimuli the intensity does not influence the force. T hese findings are explained by the assumption that the changes of forc e reflect the changes of unspecific activation level evoked by immedia te arousal. Thus, the different behaviour of force for these two modal ities is in agreement with the common view that loud auditory stimuli are arousing while intense visual ones are not.