stop-signal paradigm varies with response force

on a choice reaction task and on three tasks with respectively 100%, 80%, and 50 % response probabilities. Stop signals were presented on 30 % of the trials, instructing subjects to withhold their response. Response force on non-signal (go) trials and the duration of response inhibition on signal (stop) trials increased as response probability decreased. This pattern of findings was interpreted to support the hypothesis predicting that stopping is more difficult when response readiness is low than when it is high