Evidence for selective adjustments of inhibitory control in a variant of the stop signal task

The ability to inhibit actions inappropriate for the context is essential for meeting the shifting demands of complex environments. The stop signal task (SST) has been used in many previous studies to examine the interactions between go and stop responses in a cognitively demanding task involving attention, conflict resolution, and motor plan selection. The current study uses a variant of the SST, in which the continue signal instructs participants to proceed with the go response they were preparing. Reaction times (RTs) on continue trials were bimodally distributed, suggesting that an aspect of inhibition was involved in at least some of the trials. We investigated whether the cognitive processes delaying the generation of a behavioural response on continue trials are the same as for stop trials. We found improvement of stop signal reaction times (SSRTs) following stop trials, but the decrease in continue signal reaction times (CSRTs) was not significant. No improvement in either SSRT or CSRT was found following continue trials, suggesting that activation of the processes delaying the response on continue trials is insufficient to drive subsequent adjustments in SSRT or CSRT. In addition, go RTs only slowed following stop trials. These effects may suggest the presence of a selective learning process, which requires that the initial inhibition captured by SSRT and CSRT be combined with recognition of the stop signal specifically to affect subsequent performance.