Red Light, Green Light
Run on green, freeze on red. Miss the stop and you’re caught.
MEASURES
Go & stop RT
INPUT
Hold / release
TIME
~60 sec
How the test works
Stopping is harder than starting
Almost every reaction test measures how fast you can act. This one measures how fast you can stop — releasing a held action the instant the signal changes. Halting a movement already in progress uses a different brake in the brain, and it's usually a touch slower than starting one.
It pairs naturally with the Go / No-Go test, which measures withholding an action you never started. Together they cover the two halves of impulse control.
How your score grades
Instant brake
under 260 ms
Exceptional stop reaction — hard to beat
Sharp
260 – 329 ms
Quick to freeze — better than most
Average
330 – 399 ms
A typical stop reaction
Slow to stop
400 ms +
Anticipate the red a little earlier
Questions
Why measure how fast I stop?
Because halting an action already underway is a distinct skill from starting one, and almost no test measures it. Releasing a held movement uses the brain's inhibitory system, which tends to be slightly slower than initiating a movement.
Why is my stop reaction slower than my click reaction?
Stopping a movement in progress generally takes a little longer than starting one, because your brain has to override an action it is already committed to. A stop time somewhat above your simple click reaction is completely normal.
What gets me caught?
Holding for too long after the light turns red. There is a short window to release; miss it and you lose a life. Three misses ends the run before the finish line.
How is this different from Go / No-Go?
Go / No-Go measures withholding an action you never began. This measures cancelling an action already in motion. Together they cover both sides of impulse control.