Processing Speed Tests

Four ways of timing how fast you take in something simple and act on it.

Processing speed is the least glamorous thing psychology measures and one of the best measured. It is not how clever you are. It is how quickly you take in something simple, decide what it is, and act on it.

The tasks are deliberately easy. Nothing here needs vocabulary, arithmetic or a trick. The moment a task needs thinking about, it stops timing the intake and starts timing the thought.

The digit symbol substitution test hands you nine pairings and ninety seconds, and counts how many you produce. The symbol search test asks one yes or no question per row and times a single decision.

The number comparison test puts one number above another and asks whether they match, and reports a rate. The mental age test is the odd one out. It runs two reaction blocks, turns them into a speed index, and names the age band that index lands nearest.

Three of the four draw no bar and rank nobody. That is not modesty. Every published distribution for those tasks counts marks made with a pencil, and a pencil is not a button. The pages say so at length rather than borrowing a curve that would flatter or insult you by a third.

The 5 tests in this domain

Closest age bandMental Age TestTwo short blocks, one speed index, and the age band it lands nearest. The bands overlap so far that it is a curiosity.years Correct substitutionsDigit Symbol Substitution TestNine digits, nine symbols, ninety seconds. Your score is how many you got right before the clock stopped.items Median decision timeSymbol Search TestTwo symbols on the left, five on the right, one yes or no answer. The number is how long a typical decision took.ms Correct pairs per minuteNumber Comparison TestOne number above another, three digits long to nine. The score is how many pairs a minute you get right.pairs/min Correct sums per minuteMental Math TestSums arrive one at a time and you type the answer. The number is how many you get right in a minute.sums/min

Numbers and reading in this domain

DataProcessing Speed by AgeSpeed peaks young and drifts down. The gap between two people the same age is wider than the gap between decades.

What a speed task is actually timing

Split any of these tasks into steps and almost none of them are thinking.

Something appears on the screen. Your eye moves to it, in a jump rather than a smooth glide. You read it, which for a digit takes a small fraction of a second. You decide what it means, which here is deliberately trivial. Then your hand moves and a switch closes.

The last two steps have nothing to do with your brain, and they are worth roughly a third of a browser-timed number. That is not a reason to distrust the figure. It is the reason to compare it only against yourself, on the same machine.

Why the four tests do not agree with each other

Take all four in one sitting and the results will not line up neatly, and that is the interesting part.

A count against a fixed clock rewards a fast start. A median decision time does not, because a median ignores how the run opened. A rate divides one by the other. A composite of two reaction blocks measures something narrower than any of them.

Each is a different slice of the same underlying speed, cut with a different knife. A person who is quick on one and ordinary on another is common rather than odd. If they all reported the same number, three of the four would be pointless.

Speed and age, without the folklore

Timed tasks get slower with age, gradually, from about the mid twenties. It is one of the most repeated findings in the study of ageing and it is real.

It is also gentler than people expect, and it is dwarfed by the difference between two people of the same age. Processing speed by age sets out the curve as percentages, and shows how far the bands overlap.

The overlap is the part most age charts leave out. A quick person in their late sixties outpaces a slow person in their late thirties, comfortably. That is why no single score can place anybody's age. It is also why the mental age page argues against its own headline.

What is slowing down is mostly the wiring between distant parts of the brain rather than the muscles or the nerves. Some of it is not decline at all. Older adults tend to trade speed for accuracy, which a stopwatch reads as slowness.

What none of these numbers mean

A quick score here says you handled a small, simple task quickly, on this screen, on this day. It is not an intelligence score and it is not a measure of how fast you think in general.

Nothing in this hub detects, screens for or rules out any condition, and no figure on any of these pages is a diagnosis. Practice moves every one of these numbers, and what improves is the task you practised.

Something about your concentration, your reading or your reaction may have changed in a way that worries you. That belongs with a doctor rather than with a browser tab.

One run on one afternoon tells you very little about anything.
Your monitor and your mouse are inside every figure here.
Your own earlier runs are the only fair comparison we can offer.