Processing speed is how fast the brain perceives a stimulus, evaluates it and forms a response. It is measured by reaction time and tests such as "symbol–digit". It is a basic parameter: working memory and thinking depend on it.
How it is measured
Processing speed is assessed with elementary timed tasks: simple reaction (pressing when a stimulus appears; on average about 190 ms for a visual and 160 ms for an auditory signal), choice reaction and symbol search-and-substitution tasks. A slowing of reaction is considered a good index of general changes in brain function.
Why it is the foundation of cognition
According to Timothy Salthouse's processing-speed theory, its decline is one of the main causes of age-related cognitive worsening. When processing slows, operations do not have time to finish, and their intermediate results become "stale" by the next step. So a drop in speed drags down executive functions, working memory and fluid intelligence.
Processing speed and aging
Processing speed rises quickly from childhood to young adulthood and then, starting roughly in middle age, declines steadily — one of the earliest and most noticeable manifestations of cognitive aging. It is underpinned by a slowing of signal conduction and changes in the brain's white matter. Regular aerobic activity and control of vascular factors help preserve it.
Calculate using this marker
Calculators where Processing speed is used directly:
Frequently asked questions
Can processing speed be sped up?
Not dramatically — it is largely an innate parameter tied to brain health. But regular aerobic exercise, good sleep and control of blood pressure and blood sugar help slow its age-related decline.
Why does “everything get slower” with age?
Over the years, the speed of signal conduction falls and the brain's white matter suffers. A slowing of processing is one of the earliest manifestations of cognitive aging and partly explains the worsening of memory and attention.