A reaction time test is a simple yet effective way to measure how quickly a person can respond to a specific stimulus. It evaluates the speed at which the brain perceives information and sends a response to the body, typically through a key press, screen tap, or physical movement.

These tests are commonly used in various fields, including sports science, psychology, and neuroscience, to assess alertness, focus, and overall cognitive function. The stimulus could be visual (like a light or color change), auditory (a beep or word), or tactile (a vibration), and the participant must respond as quickly as possible after detecting it.

The results, usually measured in milliseconds (ms), can reveal differences in cognitive processing speeds, fatigue levels, or the effects of distractions or substances like caffeine. While one test might give a snapshot, multiple trials help paint a more accurate picture of someone's average reaction time and consistency.