Is processing speed part of IQ?

Yes. The Wechsler scales report a Processing Speed Index built from timed subtests such as Symbol Search and Coding, alongside verbal, visual-spatial, fluid reasoning and working memory indexes.

What's Your IQ

What is a processing speed test?

A processing speed test measures how quickly and accurately you can carry out simple visual tasks, such as scanning for a symbol, copying a code or comparing two strings. Each item is easy; your score is how many you get right in a fixed time.

HOW IT'S SCOREDcorrect answers ÷ timeWrong answers don't add to the count, so racing only pays if you stay accurate.

ONE OF FIVE WECHSLER INDEX SCORESWAIS-IV and WISC-V: Processing Speed comes from Symbol Search and Coding

Verbal comprehension

Visual spatial

Fluid reasoning

Working memory

Processing speed

WHAT MOVES YOUR SCORE

← sloweryour usual speedfaster →

SlowerAgeTypically fastest in young adulthood, then slowing gradually across adult life: one of ageing research's most consistent findings.

SlowerSleep loss and fatigueBeing tired slows simple decisions and adds lapses, even when you feel alert.

FasterPractice on the taskYou learn the layout, the key and a scanning rhythm. That's why retests often score higher.

FasterA clear strategyScan in a fixed order and commit quickly, rather than checking each item twice.

Symbol search

Symbol coding

Same or different

01:00.0

Round 1 of 3: Symbol searchTwo pink target symbols sit next to a row of five. Answer as fast as you can: is either target in the row?

F = yes · J = no, or tap the buttons

[object Object][object Object]

[object Object][object Object][object Object][object Object][object Object]

Is either pink symbol in the row?

correct 0errors 0

TOTAL CORRECT IN 3 MINUTES0

This test isn't normed, so it doesn't convert to an index score. Compare your own runs: practice effects are large on speed tasks, so improvement on a retest is expected.

Symbol search

0correct per minute

Accuracy—

— per item · 0 errors

Symbol coding

0correct per minute

Accuracy—

— per item · 0 errors

Same or different

0correct per minute

Accuracy—

— per item · 0 errors

Errors cost you: accuracy dropped below 85%. Slowing down slightly would likely raise your correct count.

THE SPEED–ACCURACY TRADE-OFF

Going faster costs mistakes, up to a point

Rush every decision and errors climb; slow right down and you gain little extra accuracy while your score falls. Drag the slider to see why the best scores come from the middle of the curve. The curve is illustrative, not fitted to data.

Time spent per item700 ms

86items per min

93%accuracy

74net correct per min

Near the sweet spot: fast enough to finish many items, careful enough that few are wrong.

Correct per minute (left axis)Accuracy (right axis)Sweet spot

SPLIT TIMES

150 years of timing the mind

From the first reaction-time experiments to today's IQ batteries, measuring mental speed has always meant measuring simple tasks very precisely.

SPLIT 11868Donders' subtraction method.Franciscus Donders times simple and choice reactions and subtracts them to estimate the duration of a mental decision.

SPLIT 21917Army Beta.The US Army's nonverbal test for recruits includes a timed digit–symbol coding task.

SPLIT 31939Wechsler–Bellevue.David Wechsler includes Digit Symbol in his new adult intelligence scale; its descendant, Coding, is still used.

SPLIT 41996Salthouse's speed theory.Timothy Salthouse argues that slowing processing speed explains much of the age-related decline in other cognitive abilities.

SPLIT 52008A speed index.The WAIS-IV reports a Processing Speed Index from Symbol Search and Coding, with Cancellation as an optional subtest.

AFTER THE CLOCK STOPS