Reaction-Time
Variability Instrument

Go / No-Go · Ex-Gaussian

A browser implementation of the sustained-attention paradigm used in attention research. It records every response to sub-frame precision and decomposes your reaction times into the three parameters that matter — not just an average, but the consistency of your responding and the rate of attentional lapses.

The task

K
A letter flashes in the centre. Press SPACE as fast as you can for every letter…
X
…except X. When you see X, do nothing — hold your response.

Most trials are “go”, so the rhythm pulls you toward pressing automatically. The rare X is where impulse control shows up. On a phone, tap anywhere instead of SPACE.

Session length
Advanced timing parameters
Find a quiet moment. Timing fidelity depends on a focused, single-tab environment.

This is a research-style measurement instrument and an educational demonstration — not a medical or diagnostic device. A single session is noisy, the scores overlap heavily with the general population, and stimulants improve these measures in people with and without ADHD alike. Nothing here can confirm or rule out a condition or guide medication decisions; that's a clinician's job.