A well-studied phenomenon known as the Flynn effect suggests that IQ scores have been rising for decades.
But a recent study of 30,000 Americans found that their vocabulary, a key component of intelligence, has not shown such an increase.
That’s an odd development. After all, more students are graduating from high school today than in the 1970s.

And more of these high school graduates go on to college. If more education leads to greater verbal skills, then vocabulary should increase.
The new study was based on the General Social Survey (GSS), a demographically representative sample of Americans over the age of 18.
The GSS was introduced in 1972 and is still running today. It collects information about the attitudes, behaviors, and concerns of people living in the United States.
The number of GSS respondents included in the current study was almost 30,000.
More graduates, but poorer knowledge of vocabulary
Part of the GSS is a 10 – Vocabulary test question. Respondents are also asked to indicate their highest level of education.
Researchers found that educational attainment has increased over the decades, as expected, from an average of 11.83 years in 1974 to 13.68 years per year 2016.
And, also as expected, years of education correlated strongly (0.47) with vocabulary, implying that people with higher levels of education generally have better vocabulary skills.
But Americans’ scores on the GSS vocabulary test didn’t change much between 1974 and 2016. And this despite the fact that many more people are graduating from high school and college.
When the researchers accounted for years of education, vocabulary scores actually decreased.
In particular, those with a bachelor’s or college degree have had the largest declines: the vocabulary of American college graduates has decreased by more than half a standard deviation over those four decades.
Likewise, vocabulary also declined among people who did not go to college.
The Average American Vocabulary is Declining
The vocabulary gap between educational levels has narrowed significantly.
The gap between early school leavers and university graduates has narrowed the most.
From 1974 to 1979, the difference between these two groups on the GSS vocabulary test was approximately 3.4 correct answers (out of a possible 10).
But by 2016, this difference had decreased to 2.9 correct answers.
The authors propose several reasons to explain this decrease.
One is that over the decades, high school students have spent less and less time reading.
Correspondingly, the verbal SAT scores in the SAT also decreased in the same period (PDF).
Another possibility is that some of the words in the test have gone out of fashion and are now less well known.
Or, more generally, perhaps American culture itself has “become less intellectual, either because of or in response to a reduction in verbal ability among those who read books.”
In everyone Case In this case, “a higher level of education did not result in improved verbal ability,” the authors write.
And as a result, “The average vocabulary of an American college grad is now lower than it was in the past.”
A 2016 study estimated that the average vocabulary of an American is about 100% is 42,000 words by age 20.
Research:“Declining Vocabulary Among American Adults Within Educational Levels, 1974-2016” (Link)Authors: Jean M. Twenge, W. Keith Campbell and Ryne A. ShermanPublished in: Intelligence, Volume 76, September-October 2019 DOI: https:// doi.org/10.1016/j.intell.2019.101377Photo:by Yaroslav Shuraev from Pexels
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