Are Americans Getting Less Intelligent? Study Reveals Concerning Trend in IQ Scores

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A new study from Northwestern University has found a reverse “Flynn effect” in a large U.S. sample between 2006 and 2018, where ability scores in verbal reasoning, matrix reasoning, and letter and number series showed consistent negative slopes, but scores in 3D rotation increased from 2011 to 2018. The composite ability scores were also lower for more recent samples, with differences being present regardless of age, education, or gender.

However, this doesn’t mean their mental ability is lower.

  • Scores of verbal reasoning, matrix reasoning, and letter and number series declined; scores of 3D rotation generally increased
  • The study provides evidence of a reverse ‘Flynn Effect’ in the U.S. between 2006-2018 for composite scores
  • ‘If all the scores were going in the same direction, you could make a nice little narrative about it, but that’s not the case’

IQ scores have shown a significant increase from 1932 through the 20th century, with differences ranging from three to five IQ points per decade. This phenomenon is known as the “Flynn effect.”

However, Northwestern University recently conducted a study that uncovered evidence of a reverse “Flynn effect” in a large U.S. sample between 2006 and 2018, with every category except one being affected. The study revealed consistent negative slopes for three out of the four cognitive domains.

Ability scores of verbal reasoning (logic, vocabulary), matrix reasoning (visual problem solving, analogies), and letter and number series (computational/mathematical) dropped during the study period, but scores of 3D rotation (spatial reasoning) generally increased from 2011 to 2018, the study found. Composite ability scores (single scores derived from multiple pieces of information) were also lower for more recent samples. The differences in scores were present regardless of age, education, or gender.

Despite the decline in scores, corresponding study author Elizabeth Dworak said she doesn’t want people to read these findings and think, “Americans are getting less intelligent.”

“It doesn’t mean their mental ability is lower or higher; it’s just a difference in scores that are favoring older or newer samples,” said Dworak, a research assistant professor of medical social sciences at Northwestern University Feinberg School of Medicine. “It could just be that they’re getting worse at taking tests or specifically worse at taking these kinds of tests.”

The study was recently published in the journal Intelligence.

The scientists used the Synthetic Aperture Personality Assessment (SAPA) Project, a free survey-based online personality test that provides test-takers feedback on 27 temperament traits (e.g. adaptability, impulsivity, anxiety, humor) and their ability scores. The study examined survey responses from 394,378 Americans between 2006 to 2018 to examine if cognitive ability scores changed within the U.S. in those 13 years.

A smaller subset of participants (303,540) was recruited between 2011 and 2018. The 3D rotation data only exists for those who took the survey between 2011 and 2018.

Why the decline in IQ scores?

While the study didn’t examine the reason for the decline in IQ scores, Dworak said there is no shortage of theories in the scientific community, including poor nutrition, worsening health, media exposures, and changes to education.

“There’s debate about what’s causing it, but not every domain is going down; one of them is going up,” Dworak said. “If all the scores were going in the same direction, you could make a nice little narrative about it, but that’s not the case. We need to do more to dig into it.”

To that end, Dworak and her colleagues are currently trying to access a dataset that contains 40 years of data to conduct a follow-up study.

A shift in perceived values in society also might have affected scores, Dworak said.

“If you’re thinking about what society cares about and what it’s emphasizing and reinforcing every day, there’s a possibility of that being reflected in performance on an ability test,” Dworak said.

She gave the example that there’s been more emphasis on STEM education in recent decades, but does that mean other areas, like abstract reasoning, are receiving less attention in schools?

Another factor could be due to a decline in motivation, Dworak said. Because the SAPA Project is advertised as a personality survey, individuals seeking out the test may be more engaged with sections related to measuring temperament and less engaged with sections that are seemingly unrelated to personality.

Reference: “Looking for Flynn effects in a recent online U.S. adult sample: Examining shifts within the SAPA Project” by Elizabeth M. Dworak, William Revelle and David M. Condon, 2 March 2023, Intelligence.
DOI: 10.1016/j.intell.2023.101734

The study was funded by the National Science Foundation.

11 Comments on "Are Americans Getting Less Intelligent? Study Reveals Concerning Trend in IQ Scores"

  1. This trend has been very evident just by observation. My theory is a combination of factors..the massive amounts of pollution and heavy metals (neurotoxins exposure is quite high) and electronics use (certain activities and man made emf exposures in general). Our societies move to more convenience and easier lifestyles is probably fostering a lazier mentality in general as well. People just don’t seem to have much intellectual drive or curiosity, but that could be a secondary result from the former.

  2. stephen schaffer | April 11, 2023 at 9:35 am | Reply

    As in the above comment, simple observation is frightening when you listen to the inability to speak proper English and think logically. Does devoting one’s life to staring at a screen develop IQ? Naw.

  3. “… letter and number series (computational/mathematical) dropped during the study period …”
    It has long and often been said that mathematics is the language of science. Science is the basis of the technologies that support modern societies. The decline does not bode well for the future.

  4. Sterling hook | April 11, 2023 at 1:11 pm | Reply

    6th paragraph (single sentence) text duplication- journal. Decline in verbal reasoning domain?

  5. Maybe Darwinism can explain the results. When the environment is tough, competition for survival is intense, and only the fittest survive, thus improving a species. Conversely, when the environment is forgiving, a reasonable life can be led without much stress, and most people can survive, thus reducing the average ability.

    It seems that studies should be done in different geographies (provided they have the historical data).

  6. Maybe it’s a sign that the IQ test is outdated. Society isn’t foolish enough to want to be brainwashed into being workers. We are seeing that calculus doesn’t help you buy a home or feed your family. Maybe it’s time we start measuring things that matter like how someone treats others, or how prepared for real life students are, maybe emotional intelligence should be looked at. Maybe then we’d have a better way to do things like predict mass shooters instead of the next of millions of engineers (who muck up everything in real world application). Let’s stop worrying about they’re, their, and there and start worrying about what that electronic device is teaching your children, like to have a 2 second attention span.

    • Desmond obanor | April 12, 2023 at 1:54 pm | Reply

      Your own term of saying that the IQ test is outdated is a way of mocking the glory of knowledge, you say that calculus will not help you buy a home neither will it help you feed your family, but you have forgotten so soon that it is because of the curiosity of knowledge and the undying desire for science as a whole that have brought the whole world into a more conduscive and a stress free life. In the 18th or 19th century if humans had just sat down and said is best we think of how to get a home and how to feed the family and not how to study calculus or how to find solutions to scientific problems, i bet you that life would had not been so conduscive for living, so my advice is that the americans and nation wide should step up their IQ level and we should not be so comfortable on the position we find ourselves now.

    • You say that you have seen that Calculus doesn’t help you buy a home.
      Calculus based science and technology careers generally lead to more renumerative and more stable careers. So it does seem that knowledge of Calculus and home ownership would be highly correlated.

  7. Has no one considered the millions of immigrants from historically low-IQ nations into the US? You can also see a decline in IQ in Scandinavian countries and when the decline started. There’s a strong correlation in mass immigration.

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