Stop‑Change Task

The Stop‑Change task assesses response inhibition and flexibility. Participants respond to a left/right arrow with F (left) or J (right), but on some trials the stimulus is withdrawn (stop signal) and on others the arrow flips (change signal).

A left/right arrow appears and you respond with F/J. In stop trials, the stimulus is withdrawn after a stop‑signal delay (SSD) and the correct action is to withhold any response — a keypress at any point in the trial counts as a failed inhibition. In change trials, after a change‑signal delay (CSD) the arrow flips and you should respond to the NEW direction; pressing the direction that was shown before the flip, or responding before the flip, is scored as an error. Responding to the wrong direction is always an error.

We report mean reaction time on correct Go trials (Mean Go RT), the success rate of Stop trials, and the success rate of Change trials (a correct response to the new direction). The SSD adapts up/down in 50 ms steps across stop trials, and the CSD adapts the same way across change trials (success makes the next signal delay 50 ms longer, failure 50 ms shorter, within 50–850 ms), keeping success rates near the middle of the range. We also show mean-method estimates: SSRT ≈ Mean Go RT − Mean SSD, and CSRT ≈ Mean Go RT − Mean CSD, where the mean signal delays are averaged over the staircase-converged trials (a mean method, not the integration method). Estimates show "—" until at least one stop/change trial and one valid go trial have been recorded.

Faster Go RT reflects baseline speed. Higher Stop success suggests stronger inhibitory control, while higher Change success indicates better cognitive flexibility and rapid re‑mapping of responses under signals. Like all single-session scores, these estimates are noisy and descriptive only.