A new study suggests that Americans" IQ scores have dropped recently, a finding that scientists are ... [+]
American IQ test scores have dropped during a recent 13-year period, a remarkable finding that runs counter to the well-established trend of increasing IQ scores throughout much of the 20th century.
That’s a main result reported in a new study published in the journal Intelligence, entitled 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.
The study found evidence of a reverse “Flynn effect” in a large U.S. sample of almost 400,000 individuals tested between 2006 and 2018 in several ability areas. The Flynn effect refers to the well-replicated finding that IQ scores increased consistently through much of the 20th century, with increases ranging from three to five IQ points per decade.
As part of the study, the authors analyzed data from the Synthetic Aperture Personality Assessment (SAPA) Project, an online test that taps 27 personality traits (e.g. adaptability, impulsivity, anxiety, humor) as well as several categories of cognitive abilities. SAPA responses were available from 394,378 Americans. In addition, a smaller subset of participants (303,540) recruited between 2011 and 2018 provided data on a measure of spatial reasoning ability.
Ability scores dropped in three areas:
- verbal reasoning (logic, vocabulary),
- matrix reasoning (visual problem solving, analogies),
- and letter and number series (computational/mathematical).
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Scores increased in one area: 3D rotation (spatial reasoning).
Composite ability scores that were derived from multiple pieces of information were also lower among more recent samples of tested adults. The differences in scores were found regardless of participants’ age, education or gender.
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Despite the declines, the senior author of the study, Northwestern University’s Elizabeth M. Dworak, cautioned against interpreting the findings as an indication that “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.”
Why The Decrease?
The study does not answer the question of why the decline in IQ scores was observed during this period. “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.”
Possible explanations for the downward direction include a shift in educational practices and emphases, a biased sample of adults who responded to the online SAPA instrument, differences in motivation among people taking this test versus those who are tested for different reasons, and differences between this instrument and the standard IQ tests used in other research.
More research will be needed to explore the possible explanations for the phenomenon. Dworak and her colleagues are currently trying to examine a dataset containing 40 years of information to conduct a follow-up study.
