Does IQ decline as we age? One type of intelligence comes in your twenties: ScienceAlert

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

If it does, at what speed? Do different types of intelligence decline at different rates?

In order to delve 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 like solving puzzles, some on how quickly you can complete a task,” says Michael Thomas, expert in psychology and neuroscience from Birkbeck University in England.

“Your intelligence will be the average of your scores on these tasks, compared to how well other people do.”

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

IQ stands for “intelligence quotient” and is a score that is standardized relative 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 will be below 100.

Does a person’s IQ change with age?

An individual’s IQ does not change with age.

In other words: If you took an IQ test now and then another one 10 years from now, your IQ score will probably be very similar. This is because IQ is always measured relative to other people your age.

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

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

Meiran Nachshon, a psychology expert at Israel’s Ben-Gurion University, agrees, saying:

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

To support this, he highlights a publication that found a strong correlation between people’s IQ at age 11 and age 90.

Does the average IQ of the population change with age?

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

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

Kaufman explains how this works:

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

“In my research, we define young adults as being in their 30s (usually between the ages of 25 and 34). That way, young adults will have an average IQ of 100 because that’s how they develop norms. When we compare adults around the world. life to young adults that will tell us how IQ changes as we get older.”

Kaufman says that when these tests are done, “[a] clear 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.

“Global IQ is an amalgam of different types of intelligence, the most studied being fluid intelligence and crystallized intelligence which, together with skills called working memory and processing speed , combine to produce a global or full-scale IQ,” says Kaufman.

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

These different types of intelligence show different patterns as you get older.

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

Fluid intelligence drops much faster. Kaufman reveals that it “peaks at age 20-24 (100), gradually declines to 99 (25-34) and 96 (35-44) before beginning a roller-coaster decline to 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 twenties, but (as long as you don’t develop dementia) your vocabulary knowledge will increase throughout your life.

“In the late sixties, most of the cognitive skills that are based on things you’ve learned (so-called crystallized knowledge) increase or are quite resistant. The speed at which you can do things can decrease.”

Food to take away:

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

May the facts accompany you!

Article based on expert answers to this question: Does IQ decline with age?

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

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