Reaction Time Test Methodology

What this test measures

The test records elapsed browser time between the visual panel entering its green state and activation of the test button. It is a simple visual reaction task: one cue and one response. It is not a clinical psychomotor vigilance test, neurological examination, or certified timing system.

Five-round protocol

1. Activate the test button to begin a round.
2. Wait through a randomized delay between 1.5 and 4.5 seconds.
3. Activate the button after it turns green.
4. An activation during the waiting state is rejected as an early attempt and the round is retried.
5. After five valid attempts, the score card is calculated.

Calculations

Median: the middle value after sorting the five attempts. This is the headline score because it is less sensitive than the mean to one unusually fast or slow attempt.

Average: the arithmetic mean of all five attempts. Best and worst are the minimum and maximum. Spread is worst minus best.

Consistency: a session-only description based on spread: very consistent at 20 ms or less, consistent at 40 ms or less, variable at 70 ms or less, and highly variable above 70 ms. These labels do not claim a population percentile or medical meaning.

Browser timing

The timer uses performance.now(), which the W3C High Resolution Time specification defines against a monotonic clock. Browsers may reduce exposed resolution for privacy or security. A precise clock does not remove display, input, operating-system, event-dispatch, or browser latency.

Device and protocol limitations

A frame lasts about 16.7 ms at 60 Hz and 6.9 ms at 144 Hz, but frame duration is not identical to guaranteed added latency. Displays, touchscreens, mice, keyboards, Bluetooth connections, power modes, background work, and browsers can all change a measured result. Compare sessions only on the same setup and protocol.

Local history and analytics

The most recent score cards are stored in your browser using local storage so you can compare sessions. They are not sent to Google Analytics. Analytics events record general interactions such as starting or completing the tool without including reaction-time values.

Research sources

• W3C High Resolution Time Level 3
• Woods et al. (2015), Factors influencing the latency of simple reaction time
• Wilkinson and Allison (1989), Age and simple reaction time
• Hudson et al. (2020), Sleep deprivation and vigilant attention

Corrections

Measurement or citation errors are corrected in the build source and the visible updated date changes only after a substantive revision. Report an issue through the contact page.