Fig. 1.

Stop signal paradigm. Interstimulus interval was 1,750 ms. A fixation cross was presented initially for 350 ms followed by the go stimulus for 1,400 ms (a right- or left-pointing arrow). For both the original and controlled versions of the SST, 20% of the trials involve an unpredictable stop signal (red dot) presented at a variable delay following the go signal (the stop signal delay). See SI Materials and Methods for more information about the staircase procedure. During the controlled version of the SST, a further 20% of trials involve a continue signal (green dot) presented with the same stop signal delay as the previous stop signal.