Does IQ decline with age? One type of intelligence peaks at twenty: ScienceAlert

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

If so, at what speed does it do it? Do different types of intelligences decline at different rates?

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 with a set of tests, for example some for language skills, other non-verbal skills like puzzle-solving, and others for how quickly you can complete a task,” says Michael Thomas, expert in psychology and neurobiology at Birkbeck University in England.

“Your intelligence will be the average of your performance on these tasks compared to how well other people are doing.”

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

IQ stands for “Intelligence Quotient” and is a standardized score for 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 individual IQ change with age?

Individual IQ does not change with age.

In other words: if you have taken an IQ test every now and then, and then 10 years from now, your IQ result will likely be very similar. This is because IQ is always measured in relation to other people your age.

“IQ is always calculated according to a person’s age, whether it is 10, 15, 25, 50, 72 or 88. So 25-year-olds are compared to other 25-year-olds for the number of items that correctly correspond to every task, just like 50-year-olds are compared to other 50-year-olds, ”explains Alan Kaufman, intelligence testing expert at Yale University in the US.

“For each age group, the mean or mean IQ is set to 100. We cannot directly compare the mean IQ across the adult age bracket because, by definition, each group will average 100.”

Meiran Nachshon, an expert in psychology at Ben-Gurion University in Israel, agrees, saying:

“IQ indicates a person’s relative positioning in relation to the mean. This relative positioning is extremely stable. “

In support of this, he emphasizes the publication, which found a strong correlation between the IQ of people aged ~ 11 and ~ 90 years.

Does the population mean IQ 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.

Usually this is not possible for the reasons described above, instead another method is needed.

Kaufman explains how it works:

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

“In my research, we define young adults around the age of 30 (usually 25-34). In this way, young adults will have an average IQ of 100, because this is how the norms arise. life expectancy for young adults who will tell us how IQ changes with age ”.

Kaufman says that after performing these tests, “[a] marked decrease [in IQ] is obvious”.

Not all types of intelligence are falling 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 readily studied of which is fluid and crystallized intelligence, which together – along with abilities called working memory and processing speed – are combined to produce a global or full-scale IQ,” says Kaufman.

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

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

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

Fluid intelligence drops much faster. Kaufman reveals that “the peak at the age of 20-24 (100 years) gradually drops to 99 (25-34) and 96 (35-44) before the roller coaster starts, it drops 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 is around twenty, but (unless you develop dementia) your knowledge of the vocabulary will increase throughout your life.

“In the late 1960s, most of the cognitive skills that rely on things you’ve learned (so-called crystallized knowledge) either increase or are quite resistant. The speed at which you can do things may drop. “


Your individual IQ won’t change with age, but on average our intelligence does decline with age.

Let the facts be with you!

An article based on experts’ answers to the question: Does IQ decline with age?

This expert response was published in collaboration with the independent fact-checking platform Subscribe to their weekly newsletter here.

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