Fig 2. Example time course of events in the inhibitory control tasks.

(a) In the simple Go/No-Go, participants pressed the left or right key to indicate the location of the green square (Go trials), but withheld their response when the square was red (No-Go trials). (b) In the complex Go/No-Go, participants pressed the left or right key to indicate the location of the coloured square (Go trials), but withheld their response when a blue square followed a yellow square (No-Go trials). In both tasks 25% of trials were No-Go, as in previous studies (e.g. [29]), so that non-responses were infrequent and thus harder to inhibit, and the inter-stimulus interval was jittered between 600 and 800 ms. (c) In the numerical Stroop, participants pressed the key corresponding to the number of digits on the screen. On congruent trials, the number of digits and the digits themselves matched, while on incongruent trials they differed and participants had to inhibit the representation of the digits. Fifty percent of trials were incongruent as in prior tests of semantic inhibition (e.g. [21]) to maintain high levels of conflict and allow accuracy and RT comparisons between trial types. Stimuli remained on the screen until the participant responded or for a maximum of 1500 ms.