Effects of stop signal modality, stop signal intensity and tracking method on inhibitory performance as determined by use of the stop signal paradigm.

In Experiment 1, the effects of stop signal modality on the speed and efficiency of the inhibition process were examined. Stop signal reaction time (SSRT) and inhibition function slope in an auditory stop signal condition were compared to SSRT and inhibition function slope in a visual stop signal condition. It was found that auditory stop signals compared to visual stop signals enhanced both the speed and efficiency of stopping. The modality effects were attributed to differences in the neurophysiological processes underlying perception. However, Experiment 2 demonstrated that the modality difference was larger for 80 dB(A) auditory stop signals than 60 dB(A) auditory stop signals. This effect was reconciled with the suggestion that loud tones are more capable of eliciting immediate arousing effects on motor processes than weak tones and visual stimuli. The second purpose of the present investigation was to explore the utility (and potential advantages) of an alternative way of setting stop signal delay relative to mean reaction time (MRT). The method that was suggested compensates for inter-individual differences in primary task reaction speed by setting stop signal delays as proportions of the subjects' MRT.