Average reaction time: normal values, what affects them, what they mean
Reaction time is the oldest measurement in experimental psychology. Franciscus Donders measured it in 1868 with mechanical apparatus, and the principle is unchanged: a stimulus appears, a key is pressed, the time in between is recorded. The values are well researched, and they say more than such a simple task would suggest.
The variants
- Simple reaction time. One stimulus, one response. The panel turns green, you tap. There is nothing to decide.
- Choice reaction time. Several possible stimuli, each with its own response. Four panels, tap the one that lights up. Time grows with the number of alternatives, logarithmically, which is known as Hick's law.
- Go/No-Go. Respond to some stimuli and not to others. Additionally measures impulse control.
Average values
For simple visual stimuli under laboratory conditions, young adults are at about 200 to 250 milliseconds. Auditory stimuli are processed faster, about 150 to 200 milliseconds, because the path from ear to cortex is shorter. Choice reaction times with four alternatives are around 350 to 450 milliseconds.
On touchscreens and in the browser, device latencies are added: screen refresh, touch detection, software. Depending on the device that is 30 to 80 milliseconds that sit in the number but have nothing to do with the person. That is why averages in web tests are around 250 to 300 milliseconds. For comparing yourself over time it does not matter as long as the device stays the same. For comparing with laboratory values it does.
What affects the numbers
- Age. Reaction time is shortest in the mid-twenties and rises slowly afterwards, about two to four milliseconds per decade for simple stimuli, more for choice reactions.
- Sleep. A night of less than five hours measurably lengthens reaction time and above all increases the number of outliers. That is why the Psychomotor Vigilance Test is standard in sleep research.
- Caffeine. Shortens reaction time by about 10 to 20 milliseconds for a few hours.
- Time of day. Most people are fastest in the late morning and early evening, slowest after lunch and in the early hours.
- Alcohol. Even at 0.05 percent blood alcohol, reaction time rises clearly, and its variability even more.
The link to intelligence
Since Arthur Jensen's work in the 1980s it has been known that reaction time and intelligence are related, with correlations around 0.3 to 0.5. More interesting than the mean is the spread: people with higher test scores react not only somewhat faster but above all more consistently. The standard deviation of a person's reaction times across many trials correlates more strongly with the general factor than the mean does.
The usual explanation is that both go back to the same underlying quantity, often described as processing speed or neural efficiency. That is a correlation, not a training instruction: practising your reaction time makes you faster at it, not more intelligent. The evidence is summarised under Can you train your IQ?
Measuring it meaningfully
Single values are almost worthless because reaction time varies by 50 milliseconds and more from trial to trial. What is informative is the median over at least five trials and the trend over days. Anyone who measures at the same time of day on the same device sees a stable baseline after two weeks, and deviations from it mean something: lack of sleep, an oncoming cold, too much or too little caffeine. In the app's lab, reaction time is therefore set up as the median of five trials with a trend curve, not as a best score.
Sources
- Donders, F. C. (1868/1969). On the speed of mental processes. Acta Psychologica, 30.
- Hick, W. E. (1952). On the rate of gain of information. Quarterly Journal of Experimental Psychology, 4(1).
- Jensen, A. R. (2006). Clocking the Mind: Mental Chronometry and Individual Differences. Elsevier.
- Deary, I. J., Der, G., Ford, G. (2001). Reaction times and intelligence differences: A population-based cohort study. Intelligence, 29(5).
Frequently asked questions
What is a good reaction time?
For simple visual stimuli, young adults are at about 200 to 250 milliseconds. On touchscreens and websites, 30 to 80 milliseconds of device latency are added, so 250 to 300 is normal there.
Is reaction time related to intelligence?
Yes, moderately. The correlation is around 0.3 to 0.5, and the variability of reaction time is more strongly related to intelligence than the mean.
Can you improve your reaction time?
Practice improves it by 10 to 30 milliseconds, then the effect saturates. Sleep, caffeine and time of day have a larger short-term influence than training.
IQ Prep drills exactly these item types under test conditions, with an explanation after every answer. Free to try, full version $4.99 one time, no subscription.
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