Stop signal task with an SSRT estimate you can check

A successful stop produces nothing to time. On every other timed task the thing measured ends in a keypress with a timestamp on it; here success is the absence of a response. What can be observed is how often the response escapes at a given delay, and the later the bar comes, the more often going wins. The estimate reads stopping latency out of that relationship using a horse race — Logan & Cowan (1984), On the ability to inhibit thought and action: A theory of an act of control, Psychological Review: going starts when the arrow appears, stopping starts when the bar appears, and whichever finishes first decides the trial.

At the delay where you press exactly half the time, the stopping process must finish where half of your go responses fall. So the delay moves 50 ms later after every successful stop and 50 ms earlier after every miss — from 200 ms, between 0 and 800 ms — which settles on 50% by construction. Your go times are ranked, choice errors included, the time at the rank matching your response rate on stop trials is read off, and the mean delay is subtracted. Published estimates fall in 150-250 ms (Verbruggen et al. (2019), A consensus guide to capturing the ability to inhibit actions and impulsive behaviors in the stop-signal task, eLife); that is a span across studies rather than a distribution, so your figure is placed beside it and never converted into a rank.

• Waiting for the bar. Answering more slowly than you naturally would makes stopping easy, the staircase answers by pushing the delay later, and the number ends up describing your patience. The run compares your go speed in the first and last quarters and prints the drift.
• A violated race. The responses that escape the bar must be your quicker ones. If the mean time on failed stops comes out above your ordinary go time, going and stopping were not independent and the arithmetic does not apply — the run checks and says so.
• A drifted rate. The response rate on stop trials is printed with a Wilson interval, so you can see whether half is even inside it.
• A short run. Thirty-two stop trials is fewer than the consensus guide asks for, and nothing on the page can fix that; the spread of the staircase reversals printed beside the estimate shows what it cost.

The same executive machinery measured through rule-switching instead of cancellation is the Wisconsin card sorting test, and through planning, the Tower of London test.

A reaction time here is the interval between the frame that painted the stimulus and the timestamp the browser attached to your key, both read from the same monotonic clock. What neither can see is the display pipeline behind it, so on a 60 Hz screen roughly 16 ms of every figure below is the machine rather than you. That is the timing floor: two numbers closer together than that are the same number, and this page reports no precision it cannot support.

The bar is drawn on the first frame at or after the requested delay and that paint is timestamped, so the delay used in the subtraction is the one that happened — on a 60 Hz panel it runs about a frame later than requested, and the result reports the median offset it measured.

This is a measurement exercise, not a clinical assessment. It reports what you did on this page against a stated reference and nothing more — it cannot establish ADHD, an impulse-control disorder or any other clinical condition. Only a qualified professional, working with more than a browser, can make that judgment.