Are Americans Getting Dumber? What IQ Trends Actually Show

For most of the twentieth century, American IQ-test performance went up. Recent data are messier: some abilities have fallen, one large study found spatial scores rising, and the newest Wechsler comparison still shows gains—just much smaller ones.

No, current research does not justify the claim that Americans are simply “getting dumber.” There is evidence that some U.S. cognitive-test scores have declined in recent cohorts, especially on certain reasoning tasks. But other abilities have remained stable or improved, results differ by age and ability level, and a 2024 comparison involving the newest Wechsler adult IQ test still found a positive generational gain.

The more accurate story is that America's long-running IQ rise appears to have slowed and become less consistent across abilities. That distinction matters because an average IQ score combines several cognitive domains that do not necessarily move together.

First, Americans Really Did Gain IQ Points for Decades

The historical rise is known as the Flynn effect. Older test norms repeatedly made newer generations look unusually strong because people taking the same or comparable tests tended to score higher than the generation used to create the norms.

A 2014 meta-analysis of 285 studies involving 14,031 participants estimated an average gain of 2.31 standard-score points per decade. For modern Stanford-Binet and Wechsler tests normed since 1972, the estimated gain was about 2.9 IQ points per decade.

So the old rule of thumb—roughly three IQ points per decade—was not invented from a single quirky dataset. It appeared repeatedly enough that intelligence tests have to be renormed periodically to keep the average near 100.

Then a Huge U.S. Study Found Scores Falling in Several Areas

The headline-making evidence came from a 2023 study of 394,378 U.S. adults tested through the SAPA Project between 2006 and 2018. Participants completed items from the International Cognitive Ability Resource, an open-source cognitive test.

The researchers found declines in composite ability scores, matrix reasoning, and letter-and-number-series performance. The downward pattern appeared across age, education, and gender groups. The steepest declines often appeared among 18- to 22-year-olds and people without a four-year college degree.

But there was a crucial exception: three-dimensional rotation scores increased between 2011 and 2018. Verbal reasoning also did not meet the researchers' threshold for a substantial annual decline in the 35-item analysis.

That is already enough to complicate “Americans are getting less intelligent.” If intelligence were simply collapsing across the board, we would expect the cognitive domains to move more uniformly.

The 2023 Study Does Not Represent Every American

The SAPA dataset is enormous, which makes small trends easier to detect. But it was a self-selected online sample, not a nationally representative survey in which Americans were randomly chosen and brought into a testing center. Participants voluntarily took an online personality and ability assessment.

The authors themselves warned against interpreting the result as proof that Americans' underlying mental ability had declined. Changes in test-taking behavior, education, exposure to particular problem types, or who chooses to take an online test could all affect the pattern.

This is the same sampling problem discussed in IQ Differences Between Groups: a large sample can produce a very precise estimate of the people who took the test without perfectly representing the entire population.

A Representative U.S. Adolescent Study Found No Single Trend

A separate study used a nationally representative sample of 10,073 American adolescents ages 13 to 18 and compared performance using norms from 1989 and 2003. Overall, there was no meaningful Flynn effect for the full sample.

But the average hid striking differences. Thirteen-year-olds gained about 2.3 IQ points per decade, while 18-year-olds declined about 1.6 points per decade. Scores also moved differently across ability levels: the lowest-scoring group declined while the highest-scoring group gained.

Again, there was no single national arrow. Age and ability level changed the answer.

The Newest Wechsler Evidence Still Shows an IQ Gain

The release of the WAIS-5 in 2024 provided an unusually current check on the trend. Researchers examined two counterbalanced studies from the new test's technical manual, including 186 people ages 16 to 90 who took both the WAIS-IV and WAIS-5.

The result was a Flynn effect of about 1.2 IQ points per decade. That is far below the historical expectation of roughly three points per decade—but it is still a gain, not a decline.

This may be the most useful snapshot of the current argument. The classic Flynn effect appears substantially weaker on the newest U.S. Wechsler comparison, while other recent datasets show declines in selected abilities. Calling that “Americans are getting dumber” throws away most of the actual evidence.

Why Would IQ Trends Slow or Reverse?

Researchers have proposed plenty of possibilities: changes in education, health and nutrition, family size, migration, environmental exposures, technology, media use, and the kinds of cognitive skills people practice in everyday life. Test familiarity can also change across generations.

At present, there is no clean causal verdict for the recent U.S. pattern. The 2023 SAPA study was designed to detect score trends, not to identify their cause. And when different domains move in different directions, a one-factor explanation becomes even less convincing.

Generational trends also should not be confused with what happens to one person as they age. Cognitive Train's guide to how IQ changes with age covers lifespan changes, while IQ score stability over time looks at how strongly an individual's relative standing tends to persist.

Does a Falling Test Score Mean Intelligence Itself Is Falling?

Not necessarily. IQ tests are meaningful measures of cognitive performance, but a trend in one test score can reflect several things at once: the underlying ability, familiarity with that kind of problem, motivation, test-taking style, education, and changes in the population being sampled.

This does not make IQ trends meaningless. It means the interpretation should match the evidence. A decline in matrix reasoning is evidence that newer samples performed worse on matrix reasoning. It is a much bigger leap to conclude that an entire nation has become broadly less intelligent.

Our guide to what IQ actually measures explains why Full Scale IQ is a composite rather than a single mental skill.

So, Are Americans Getting Dumber?

The best current answer is no—not in the simple way that headline suggests. Americans experienced substantial IQ-test gains for much of the twentieth century. Recent U.S. evidence suggests those gains have slowed and may have reversed for some abilities and some groups. Other abilities have improved, and the newest WAIS comparison still shows a smaller positive Flynn effect.

A more accurate headline would be: American cognitive-test trends are becoming mixed. That is less dramatic, but much closer to what the data actually show.

Check Your Own Approximate IQ

A generational trend cannot tell you how you personally score. If you want to sample your own verbal, logical, numerical, and visual-spatial reasoning, Cognitive Train's free IQ-Style Test gives a non-clinical, approximate estimate based on your performance on the test itself.

For individual measures of reasoning, memory, attention, and processing speed, browse Cognitive Train's brain tests and cognitive assessments.

The Bottom Line

Recent U.S. IQ trends do not show a uniform collapse in intelligence. They show a weaker Flynn effect, declines in some cognitive domains, gains in others, and important differences by age, ability level, test, and sample. The old three-points-per-decade rise may no longer describe modern America very well, but “Americans are getting dumber” goes far beyond what the evidence can support.

For broader context on how population averages should be interpreted, read Why Do Average IQ Scores Differ Between Countries?, browse the Intelligence & IQ collection, or explore Cognitive Train's brain training and cognitive training tools.