Oct 16, 2018 | Updated: 04:34 PM EDT

America Getting Smarter: Why Have IQ Scores Risen in the US Over the Last Century?

Mar 26, 2015 11:41 PM EDT

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A continual increase in intelligence quotient (IQ) scores over the past century seems to indicate that most Americans are smarter than their grandparents were. Is this really true? And if so, why?

The dramatic rise in IQ scores over the past century has been termed the Flynn effect, after psychologist James Flynn who discovered this trend in the 1980s. Flynn states that if a person living a century ago would have taken an IQ test and scored it against today's standards, he or she would have received an average score of 70. Meanwhile, if a person from the current generation were to take a test in accordance with prior generations' norms, he or she would score an IQ of 130.

Hypotheses pointing toward the role of genetics and nutrition have generally not satisfied the academic community, while the notion that we're geniuses and that our grandparents were mentally retarded is also regarded as illogical and improbable.  

Researchers such as David Baker, professor of sociology and education at Penn State, have tried to come up with other explanations related to a confluence of environmental factors.

"If you look at a chart of the Flynn Effect over the 20th century in the United States, for example, you notice that the proportion of children and youth attending school and how long they attend lines up nicely with the gains in IQ scores," Baker said in an interview with Futurity.

Over the last centuries, as school enrollment rates increased, so did students' exposure to activities that had a profound influence on brain development and thinking skills. Although today there is the widespread perception that the quality of school education is waning, in reality, the shift from memorization-focused learning to problem solving and abstract thinking skills has increased what he refers to as our liquid intelligence. The latter refers to the flexible thinking and abstract problem solving that scores high on IQ tests.

To measure how challenging lessons were by comparing those given at the start of the century to now, researchers analyzed more than 28,000 pages of content in textbooks published from 1930 to 2000. They measured, for example, whether students were required to learn multiple strategies to find solutions or needed other mental skills to solve problems. Additionally, a separate study was conducted in rural communities in Peru where formal education is a recent development. The results indicated that there was a dramatic spike in cognitive reasoning after student began attending school. 

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