From signal to click
When the screen turns green, light reaches your eyes, your visual cortex recognizes the change, your brain decides to act and sends a signal down to your finger muscles. For a simple visual stimulus this takes most adults about 200–250 ms. Sound is processed faster: simple auditory reactions are often 20–40 ms quicker than visual ones.
Simple vs. choice reaction time
A simple reaction test has one signal and one response — like our reaction time test. A choice reaction test asks you to respond differently to different signals, which adds decision time and typically lands 100 ms or more higher. The aim trainer adds movement time on top of both.
Hardware latency
Your result also includes delay from your equipment:
- Display: a 60 Hz screen refreshes every 16.7 ms, so the green can appear up to a frame late. Panels also add their own processing delay.
- Mouse: wireless and low polling-rate mice add a few milliseconds.
- Browser: event handling adds a small, fairly constant delay.
Together that can be 10–50 ms. It is why the same person scores differently on different computers.
Why the start is random
If the signal came at a fixed time, you could time your click instead of reacting. Good tests wait a random interval (ours uses 1.5–4.5 seconds) and treat any click before the signal as too early.