Reaction Time Test
Test your reaction time by clicking when the screen changes color.
Measures response time in milliseconds and compares to the average human reaction of 250ms.
Reaction time is the interval between the onset of a stimulus and the beginning of a voluntary motor response. It is divided into two phases: pre-motor time (neural signal processing) and motor time (muscle activation). The sum of both is measured in milliseconds (ms).
Simple reaction time formula: RT = Stimulus Detection Time + Neural Processing Time + Motor Execution Time
In practice, RT is measured directly as: RT = Response Time (ms) − Stimulus Onset Time (ms)
Hick’s Law — choice reaction time: When a person must choose between N equally likely options: RT = a + b × log₂(N)
Where:
- a = base reaction time (constant, ~150 ms)
- b = time per bit of information processed (~150 ms/bit)
- N = number of choices
Example: 1 choice → log₂(1) = 0 → RT ≈ 150 ms. 4 choices → log₂(4) = 2 → RT ≈ 150 + (150 × 2) = 450 ms.
Average reaction times by age (visual stimulus, simple RT):
| Age Group | Average RT | Elite Athlete RT |
|---|---|---|
| 10–14 | 350–400 ms | — |
| 18–24 | 190–220 ms | 150–180 ms |
| 25–35 | 200–230 ms | 155–190 ms |
| 36–50 | 230–270 ms | — |
| 51–65 | 275–325 ms | — |
| 65+ | 330–400 ms | — |
Factors that slow reaction time:
- Alcohol (+15–30% slower per drink)
- Sleep deprivation (6h sleep → equivalent to being legally drunk after 2 weeks)
- Distraction (texting while driving adds ~570 ms on average)
- Age (peaks at ~24, declines ~3 ms/year after 40)
Worked example: A driver traveling at 100 km/h (27.8 m/s) with a 250 ms reaction time: Distance covered during reaction = 27.8 × 0.250 = 6.9 meters before brakes are even applied.
Improving reaction time: regular exercise, adequate sleep, caffeine (up to ~200 mg), and sport-specific drills all measurably reduce RT by 5–20%.