Stop-Signal
Task
The stop-signal task measures something a go/no-go can't: action cancellation — how fast you can abort a movement you have already begun. A staircase keeps you stopping about half the time, and the stop-signal reaction time (SSRT) — the covert latency of the brake — is recovered from the race between going and stopping.
The task
The red signal comes later and later when you stop successfully, and earlier when you fail — so it stays genuinely difficult and you will miss roughly half. That's by design; don't slow down to wait for it, or the estimate breaks.
Only the stop trials carry information about stopping, so that is how these are counted — 25% of trials carry a stop signal, making a 50-stop-trial session 200 trials long. Below 50 the estimate gets noticeably jumpier run to run; Screening is for a quick look, not for tracking a change.
Advanced parameters
Method follows the consensus guide (Verbruggen et al., 2019, eLife): a fixed 25% stop-signal rate, a 1-up/1-down SSD staircase, and the integration method (with replacement of go omissions) for SSRT. The stop rate is deliberately not adjustable — changing it changes how much you brace for the signal, which moves the SSRT for reasons that have nothing to do with your inhibitory control. This is a research-style instrument and educational demonstration — not a medical or diagnostic device. A single session is noisy, population overlap is large, and stimulants sharpen inhibition in people with and without ADHD alike.
Stop-Signal Task
What this test measures
The stop-signal task is the standard laboratory measure of response inhibition — the ability to cancel an action already underway. You respond to arrows as fast as you can, but on a minority of trials the arrow turns red and you must abort the response. A staircase adjusts how late the stop signal arrives so that you succeed on roughly half of stop trials.
That 50% balance point is what makes the key measure computable: the stop-signal reaction time (SSRT), an estimate of how long your brain needs to cancel an action. Stopping is modelled as a race between a go process and a stop process (Logan & Cowan's race model), and SSRT is the speed of the stop runner — a covert latency you cannot observe directly on any single trial.
How to use it
Respond fast and treat failed stops as normal — they are designed to happen about half the time. Slowing down to wait for the signal defeats the estimate, and the task will flag runs where that happened. Signed-in sessions feed the stopping-ability trend on the Progress page.
Sapiens Bench tasks are educational instruments for self-tracking, not medical or diagnostic devices.