The Stop Signal Task (SST) is a widely used measure of response inhibition — the ability to cancel a planned motor action. Participants respond to left- or right-pointing arrows (go trials), but on a minority of trials the circle surrounding the arrow turns red after a short delay (the stop-signal delay, SSD), signalling that the response should be withheld.

The key theoretical construct is the Stop Signal Reaction Time (SSRT): a latent measure of how quickly the inhibitory process can be triggered, estimated by comparing go-trial RT distributions with stop-trial inhibition rates. The SST is sensitive to executive dysfunction in ADHD, OCD, substance use disorders, and normal aging, making it one of the most-used paradigms in cognitive neuroscience and clinical research.

This implementation follows the design described by Logan, Cowan & Davis (1984), using a fixed set of SSDs (200–400 ms in 50 ms steps). Two phases are included: a practice block (8 go + 4 stop trials, with correct/incorrect feedback) and a main block with 30 go trials and 10 stop trials (25% stop rate). All timing parameters are configurable in the Open Lab study builder.