Average reaction time by age: why the charts disagree

How much does reaction time really slow with age?

In a lab, very little before 60. In a browser, a lot more, and the gap widens after 50. The table lists the large studies that report a slope, along with the conditions that shape it.

The lab studies

The first four rows are where the claim "reaction time barely changes" comes from. Woods and colleagues note that their 0.55 ms figure sits inside the 0.34 to 1.7 ms range of earlier lab work. At 0.55 ms per year, the average 60-year-old is about 22 ms behind the average 20-year-old.

In the same study, one person's own trials swing about 40 ms around their own average. That swing is bigger than the age gap. So on any single day, how you feel moves your score more than your age does.

The browser dataset

The MindCrowd row is where the claim "you lose 7 ms a year" comes from. It is the biggest reaction-time dataset ever published. People took it on a web page, pressing a key or tapping the screen when a pink sphere appeared.

Its age effect is not a straight line. The paper fits a curve with a 7 ms per year linear term and a downward bend. In plain words, the slowing is gentle in your thirties and forties and steeper later. If you read 7 as a flat rate for every age, it is too big for younger adults and too small for older ones.

The touchscreen task

The UK Biobank row is a third kind of number. More than 150,000 people did a card-matching task on a clinic touchscreen. That task asks you to recognize something, not just react, and its slope came out at 3.4 ms per year between 40 and 70. The more deciding a trial needs, the more it slows each year. So the kind of task changes the answer as much as the age range does.

Why do browser datasets find ten times more slowing?

There are four reasons, and none of them is that one side measured badly.

The lab studies stop before the steep part. Every lab row in the table ends between 59 and 65. Der and Deary (2006) studied 7,130 adults from a national UK survey. They found that simple reaction time barely slows until around 50 and then speeds up. Choice reaction time, on the other hand, slows across the whole adult range. A sample that runs to 85 includes twenty years of the curve that a sample ending at 65 leaves out. Fit a straight line through each, and the longer sample will always look steeper.

Older people were on slower devices. In MindCrowd, the people who took the test on a phone or tablet averaged 54 years old, well above the group as a whole, and their reaction times were longer. A browser test can't tell an older nervous system from an older touchscreen. So some of the slowing that looks like age in web data is really the device.

Lab studies use one calibrated machine for everyone. That is why their slopes are smaller, and also why their raw numbers are lower. The guide on online reaction test accuracy covers how much a device adds.

Not everyone knows the interface equally well. A five-trial web task rewards people who already know where the key is and how the page behaves. On average, younger adults have more of that practice, and five trials leave no room to catch up. Woods and colleagues ran forty trials per condition on a fixed setup, so knowing the interface barely touched their results.

Different people show up. A 75-year-old who takes an online brain test is not a typical 75-year-old. Neither is a 22-year-old lab volunteer. Both samples lean, in different directions, and neither paper claims otherwise. So read every age chart as "people like the ones who took part", not as a rule about you.

Put those together, and the ten-fold gap stops being a contradiction. The lab number is the slope of the nervous system alone. It is measured on one machine, mostly before the slowing speeds up. The browser number adds the device, practice and who turned up, and it covers the whole adult lifespan. In our view, a page that shows an age table without saying which kind it is has left out the part you need most.

What should you expect at your age on this test?

Under 50, you get almost no age discount at all. On the lab scale, the difference between 25 and 45 is about 11 ms, which disappears inside the noise of five rounds. If your median is slower than a friend's, check your screen, your mouse and your sleep before you blame your birth year. The good reaction time chart lays out where each number falls.

From 50 on, expect a real but modest shift. The lab data say the slope gets steeper after this point, and the browser data agree. A healthy 65-year-old on a good setup can still post a median in the standard band on this test.

What changes more than the median is the spread. Older adults vary more from one trial to the next, so the median of five rounds matters more, not less.

Past 70, the numbers in the table mostly stop applying, because the lab samples end there and the browser samples thin out. What we can honestly say is that reaction time keeps slowing, and the rate varies a lot between people. Health, medication and sleep matter more than the calendar. MindCrowd found that education, smoking, dizziness and the number of daily medications all moved the number alongside age.

This site doesn't ask your age, and it won't guess it from your score. We think the only comparison that works at any age is the one with yourself: same device, same time of day, tab in front, median of five. If that median drifts over months while the conditions stay the same, you have measured something. If it jumps around from day to day, you have measured the days.

Two last practical notes.

1. The 0.55 ms figure quoted on the reaction time test page is the lab slope. It is the right one for the on-screen scale here, because the device delay grows with your hardware, not with your age.
2. If you want to know whether you have slowed, the only useful chart is your own history. The test keeps it on your device for exactly that reason.