Does IQ decline with age? A type of intelligence spikes in your twenties: ScienceAlert

Many of us are familiar with the idea that as we age, we become less mentally agile; but is it something that can be measured – does our IQ decline with age?

If so, how fast does it do it? Do different types of intelligence decline at different rates?

To dig deeper into these questions, Metafact asked five experts in intelligence, behavioral science and psychology: “Does IQ decline with age?”. Here’s what they said…

What is IQ and how is it measured?

“Intelligence is usually measured by a set of tests, for example, some on language skills, some on non-verbal skills such as solving puzzles, some on how quickly you can complete a task,” explains Michael Thomas, a psychology and neuroscience expert from the University of Birkbeck in England.

“Your intelligence will be the average of your scores in these tasks, compared to the performance of others.”

IQ tests assess different abilities such as how you retain and learn information, your abstract reasoning, and visual-spatial processing.

IQ stands for “intelligence quotient” and is a standardized score compared to other people your age.

If your intelligence is average for your age, your IQ score will be 100. If it is above average, it will be above 100 and below average below 100.

Does an individual’s IQ change with age?

An individual’s IQ does not change with age.

In other words: if you take an IQ test once in a while, then another in 10 years, your IQ score will probably be very similar. This is because IQ is always measured against other people your age.

“IQs are always calculated relative to a person’s age, whether that age is 10, 15, 25, 50, 72, or 88. So 25-year-olds are compared to other 25-year-olds. in terms of number of items, they respond correctly to a given task, just as 50-year-olds are compared to other 50-year-olds,” says Alan Kaufman, an intelligence testing expert at Yale University in the United States.

“For each age group, the average or average IQ is set at 100. We cannot directly compare average IQs in the adult age bracket because – by definition – each group will have an average of 100.”

Meiran Nachshon, a psychology expert from Ben-Gurion University in Israel, agrees, saying:

“The IQ indicates the relative positioning of an individual compared to the average. This relative positioning is extremely stable.”

To back this up, he points to a publication that found a strong correlation between the IQ of people at ~11 and ~90.

Does the average IQ of the population change with age?

To measure changes in IQ over time, we need to be able to compare the IQ of older people with that of their younger counterparts.

This is usually not possible for the reasons described above, but a different method is needed.

Kaufman explains how it works:

“The first thing we need to do is find a common ‘benchmark’ to compare adults to. We can compare the performance of 70 year olds, 60 year olds, 50 year olds, 40 year olds, etc. to the norms (group or standards) established for young adults.

“In my research, we define young adults as being around 30 years old (usually between 25 and 34). That way, young adults will have an average IQ of 100 because that’s how standards are developed. When we are comparing adults across the lifespan to young adults which will tell us how IQ changes as we age.”

Kaufman says that when these tests are done, “[a] sharp decline [in IQ] It’s obvious”.

Not all types of intelligence decline at the same rate

IQ tests measure many types of intelligence and group them together.

“Overall IQ is an amalgamation of different types of intelligence, the most studied being fluid intelligence and crystallized intelligence which, together with abilities called working memory and processing speed, are combined to produce an overall IQ or on a large scale,” says Kaufman.

“Fluid intelligence or fluid reasoning reflects the ability to solve new problems, the kind that are not taught in school,” he explains, “while crystallized intelligence or crystallized knowledge measures the learning and problem solving related to schooling and acculturation”.

These different types of intelligence show different patterns as you age.

Crystallized intelligence “averages 98 at ages 20-24, rises to 101 at ages 35-44, before declining to 100 (45-54), then 98 (55-64), then 96 (65- 69), then 93 (70–74) and 88 (75+),” Kaufman explains.

Fluid Intelligence drops much faster. Kaufman reveals that he “peaks at 20–24 (100), gradually drops to 99 (25–34) and 96 (35–44) before starting a roller coaster dive at 91 (45–54), 86 ( 55–64), 83 (65-69), 79 (70-74) and 72 (75+).”

Thomas says: “The fastest response times you’ll ever have are in your mid-twenties, but (as long as you don’t develop dementia) your vocabulary knowledge will increase throughout your life.

“By your late 60s, most cognitive skills based on things you’ve learned (so-called crystallized knowledge) increase or are quite resilient. The speed at which you can do things may decrease.”


Your individual IQ will not change with age, but on average our intelligence declines with age.

Let the facts be with you!

Article based on expert answers to this question: does IQ decrease with age?

This expert answer was published in partnership with independent fact-checking platform Subscribe to their weekly newsletter here.

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