Fig. 1.

(a) In the stop signal task, participants are instructed to respond as quickly and accurately as possible to ‘go’ stimuli in the form of left and right arrows, which are presented in a rapid and pseudo-randomised sequence. During the inhibition trials, they must try to cancel the already initiated response when an infrequent stop signal cue is presented at a short offset after the go cue. The go–stop offset is typically set to produce a 50% failure rate on the inhibition trials. (b) In the target detection paradigm, participants are instructed to monitor sequences of distractors for an infrequent target stimulus. The stimulus that is the target is periodically changed. When motor responses are made to distractors but not to targets, this design is equivalent to a go–no go paradigm.