Does IQ Decrease With Age?

Does IQ decrease with age?

Does IQ decrease with age?

Check out this answer from Consensus:

The relationship between IQ and age is complex and influenced by a variety of factors, including genetics, physical health, and lifestyle choices such as smoking. While some aspects of cognitive ability, such as fluid intelligence, may decline with age, this decline can be mediated by factors like physical health. Moreover, genetic factors play a significant role in the stability of intelligence across the lifespan. Understanding these relationships is crucial for developing strategies to maintain cognitive health into old age.


Intelligence Quotient (IQ) is a measure of a person’s cognitive abilities and potential. It is often used as an indicator of intellectual capability and potential for academic and professional success. The relationship between IQ and age has been a subject of considerable research interest, with studies exploring how cognitive abilities change over the lifespan.

Cognitive Stability and Change Across the Lifespan

The Scottish Mental Surveys of 1932 and 1947 provide a unique opportunity to examine the stability of intelligence differences across the life span, the determinants of cognitive change from childhood to old age, and the impact of childhood intelligence on survival and health in old age1. These surveys have shown novel findings on the stability of IQ scores from age 11 to age 80, including sex differences in cognitive aging and the effect of childhood IQ on all-cause and specific mortality, morbidity, and frailty in old age.

The Wilson Effect and Heritability of IQ

The heritability of IQ, which refers to the proportion of variance in IQ attributable to genetic variation, has been shown to increase with age, a phenomenon known as ‘The Wilson Effect’2. This effect suggests that as individuals age, genetic factors play an increasingly significant role in their cognitive abilities, with heritability reaching an asymptote of about 0.80 by early adulthood.

Health and Cognitive Ability

Physical health has been identified as a significant mediator in the relationship between age and fluid intelligence3. The effect of age on fluid IQ is fully mediated by physical health, while crystallized intelligence appears to be non-mediated. This implies that maintaining good health may mitigate the decline in fluid intelligence typically associated with aging.

Timing Tasks and Cognitive Performance

Research on timing tasks has revealed that both age and IQ can influence the variability of judgments of duration4. While there is an association between increasing age and decreasing IQ with increased variability, events can still be timed accurately on average.

Two-Choice Tasks and Cognitive Processing

In two-choice tasks, such as numerosity discrimination and lexical decision, aging and IQ have been shown to affect performance5. However, declines in performance with age were not significantly different for low compared to high IQ subjects, suggesting that IQ may not be a strong determinant of cognitive decline in these tasks.

Generational Changes in IQ and Aging

Investigations into generational changes in IQ have provided insights into how the relationship between IQ and age has evolved over time6. These studies have examined changes in intellectual ability across a broad age range and have considered the implications of these changes for theories of cognitive aging.

Memory Performance, Aging, and IQ

The effects of aging and IQ on memory performance have been explored in various memory tasks7. IQ has significant effects on performance, particularly on measures of drift rate in recognition tasks and recall performance. However, age also has substantial effects on certain cognitive processes, such as boundary separation and nondecision time.

Genetic Contributions to Cognitive Stability and Change

Genetic contributions to the stability and change in intelligence from childhood to old age have been estimated using genome-wide single nucleotide polymorphism (SNP) data8. This research suggests that genetic factors contribute to both the stability of intelligence across the lifespan and the changes that occur with aging.

The Differentiation of Cognitive Abilities

The differentiation of cognitive abilities during childhood and its relationship with IQ has been studied to determine when and how cognitive abilities become more distinct9. These studies suggest that age may moderate the effect of IQ on the differentiation of cognitive abilities.

Smoking and Cognitive Change

The impact of smoking on cognitive change from childhood to later life has been investigated, with findings indicating that smoking is a risk factor for relative cognitive decline10. This decline is independent of childhood IQ and other potential confounding factors.


Does IQ decrease with age?

Alan S. Kaufman has answered Likely

An expert from Yale University in Intelligence, Education

The question of how our IQs change has been researched in numerous research investigations, often using the various versions of the Wechsler Adult Intelligence Scale (WAIS), the most recent being the 2008 WAIS-IV. The results have been confirmed many times, but the research is a little tricky to conduct for two reasons: 

(A) 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 the number of items they answer correctly on any given task just as 50 year olds are compared to other 50 year olds. For every age group, the average or mean IQ is set at 100. So we can’t directly compare the mean IQs across the adult age range because—by definition—every group will average 100. 

(B) the second hitch is that different age groups differ in their education level. It is more common now than 25 or 50 years ago for people to attend college and to earn degrees. Since education is related to IQ, that variable serves as a confound in the research. If IQs go down with age, how can we be sure that any decrease is due to age rather than the lower level of education, on average, for older than younger adults? 

Both of these problems are easily handled by researchers (I have conducted a number of these investigations with my colleagues). The first thing we have to do is to find a common “yardstick” to compare adults. We can compare the performance 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 as about age 30 (usually ages 25-34). In that way, young adults will have an average IQ of 100 because that is the way the norms are developed. When we compare adults across the life span to young adults that will tell us how IQ changes as we get older. But first we have to take care of the inequity in education across the age range. That can be done statistically by “controlling” for education (even though many more 30 year olds graduated college and many more 70 year olds dropped out of high school, this statistical procedure controls for the age to age differences. 

Now we can compare Full Scale (global) IQs for adults of different ages. A clear decline is evident. The mean WAIS-IV IQ is 100 for ages 20-24 and is 99 for ages 25-44. Then it drops to 97 for ages 45-54, to 94 for ages 55-64, to 90 for 65-69, to 86 for ages 70-74 and to 79 for ages 75+. 

But global IQ is an amalgam of different kinds of intelligence, the most popularly studied being fluid intelligence and crystallized intelligence which together—along with abilities called working memory and processing speed—are combined to yield global or Full Scale IQ. Fluid intelligence or fluid reasoning (abbreviated Gf) reflects the ability to solve novel problems, the kind that aren’t taught in school, whereas Crystallized intelligence or crystallized knowledge (Gc) measures learning and problem solving that are related to schooling and acculturation. And they have very different aging curves. 

Gc averages 98 at ages 20-24, rises to 101 by ages 35-44, before declining to 100 (ages 45-54), then 98 (55-64), then 96 (65-69), then 93 (70-74), and 88 (75+). 

The decline with age in Gf—solving novel problems—is even more precipitous. Gf peaks at ages 20-24 (100), drops gradually to 99 (25-34) and 96 (35-44) before starting a roller coaster plunge to 91 (45-54), 86 (55-64), 83 (65-69), 79 (70-74), and 72 (75+). 

These values are just averages for the entire US population of adults, with the mean IQs for each age higher for more educated individuals. But the same rate of decline across the age range seems to occur for all adults, on average, whether they are semi-skilled workers or university professors. 

Two sources to consult for those interested: Essentials of WAIS-IV Assessment—2nd edition (Elizabeth Lichtenberger & Alan Kaufman), 2013, John Wiley publisher and IQ Testing 101 by Alan Kaufman, 2009, Springer publisher.


Does IQ decrease with age?

Ian Silver has answered Unlikely

An expert from University of Cincinnati in Intelligence, Behavioural Science, Social Sciences

Intelligence, like most psychological characteristics, is highly heritable. Habitability refers to the percentage of the characteristic that is accounted for by genetic factors. Approximately 67 percent of intelligence is influenced by genetic factors. In addition to these genetic factors, research has show that early life factors, such as household characteristics, influence intelligence. Approximately 10-12 percent of intelligence is influenced by these early life factors. An important characteristic of genetics and early life factors is that they don’t tend to change as we age. As such, if approximately 77-79 percent of intelligence is influenced by factors that don’t change as we age, it is unlikely for our level of intelligence to decrease as we age. Negative environmental stimuli (e.g., head trauma) and serious diseases, however, can result in declines in general intelligence. The influence of these factors can correlate with age but aging alone does not influence intelligence.


Does IQ decrease with age?

Nachshon Meiran has answered Uncertain

An expert from Ben-Gurion University of the Negev in Intelligence

I had to choose among the options which is why I chose “unlikely”. However, the real answer is more complex in my mind.

IQ indicates the relative positioning of an individual relative the the average. This relative positioning is extremely stable. A quite recent paper in Psychological Science (to the best of my memory) found a correlation of almost .70 between IQ at age ~11 to that at age ~90.

HOWEVER, the population averages are influenced by age. The best supported factorial model of intelligence is Carrol-Cattel-Horn model, according to which there are several specific abilities such as fluid, crystalized, auditory, visual, quantitiative, and speed. All of these abilities are explained by the general factor, g’. Now, all the specific abilities but one (crystalized intelligence) decline from age ~25-30 (i.e., the population average) – some (speed) decline quite dramatically.


Does IQ decrease with age?

Michael Thomas has answered Unlikely

An expert from Birkbeck, University of London in Psychology, Cognitive Science, Intelligence

Intelligence is usually measured by a set of tests, for instance, some about language skills, some about non-verbal skills such as solving puzzles, some about how quickly you can complete a task. Your intelligence will be the average of your scores across the tasks, compared to how well other people do. The concept of ‘general’ intelligence arises because a person’s scores across the set of tests tends to be similar. As you age, different skills change at different rates.

The fastest response times you will ever have are in your mid-twenties, but (so long as you don’t develop dementia), your knowledge of vocabulary will increase throughout your life. Into your late sixties, most cognitive skills relying on things you have learned (so-called crystalised knowledge) either increase or are pretty resilient. The speed with which you can do things can decline.

The short answer, then, is that your skills may diverge with age, but your overall intelligence can remain similar. For more information on whether IQ is fixed, take a look at the Centre for Educational Neuroscience’s resource:


Does IQ decrease with age?

Gavin Brown has answered Uncertain

An expert from University of Auckland in Education, Psychometrics, Statistics

Previous answers have correctly shown that certain aspects of cognitive functioning decline with age. furthermore, they were correct that with continued development of crystallised knowledge the slowing of those functions is not really apparent. However, with age comes greater probability of diseases that can impact IQ. So the answer really is uncertain; it depends on your health and how and if you continue to use your mind. If you want to know how to keep your mind going, Lord Robert Winston gives excellent advice in his book. Doing puzzles — sudoku, bingo, jigsaws, etc.–will keep your mind active solving new problems; this fights mental atrophy. Diet and exercise do too.

Winston, R. (2003). The Human Mind and How to Make the Most of It. London: Bantam.

Plus, something we often forget is that people with below average IQ tend not to survive into old age as frequently as those with above average IQ. So developing your IQ as young as possible will help you age longer and better. In good health, overall IQ does not necessarily diminish–but speed of processing will.

It depends…..

Subscribe to
Our Newsletter