What’s behind the spike in IQ scores?

It's not just increased attendance, but a more challenging learning environment that account for the IQ score rise, says David Baker. "As people went to school, what they did there likely had a profound influence on brain development and thinking skills, beyond just learning the three R's." (Credit: Jon Skilling/Flickr)

More schooling and harder problems may be the best explanation for the dramatic rise in IQ scores—often referred to as the Flynn Effect—during the past century, a new study reports.

The findings, which show that mean IQ scores of adults in the United States have increased by about 25 points, also suggest that environment may have a stronger influence on intelligence than once thought.

“There’ve been a lot of hypotheses put forward for the cause of the Flynn Effect, such as genetics and nutrition, but they generally fall flat,” says David Baker, professor of sociology and education at Penn State. “It really begged the question of whether an environmental factor, or factors, could cause these gains in IQ scores.”

Beyond the 3R’s

School enrollment in the United States reached almost 90 percent by 1960. However, it’s not just increased attendance, but a more challenging learning environment that is behind the IQ score rise, researchers say.

“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 says.

“As people went to school, what they did there likely had a profound influence on brain development and thinking skills, beyond just learning the three R’s. This is what our neurological and cognitive research shows.”

Also, over the century, as a higher percentage of children from each new generation went to school and attended for more years, IQ scores rose, Baker says. “Even after full enrollments were achieved in the US by about the 1960s, school continued to intensify its influence on thinking.”

No ‘dumbing down’

While even basic schooling activities can shape brain development, over the past century, schools have moved from learning focused on memorization to lessons that require problem solving and abstract thinking skills, which are often considered functions of fluid intelligence.

“Many like to think that schooling has become ‘dumbed down,’ but this is not true,” Baker says.  “This misperception has tended to lead cognitive scientists away from considering the impact of schooling and its spread over time as a main social environment in neurological development.”

Just as more physical exercise can improve sports performance for athletes, these more challenging mental workouts in schools may be building up students’ mental muscles, allowing them to perform better on certain types of problems that require flexible thinking and abstract problem solving, such as IQ tests.

“Certain kinds of activities—like solving problems, or reading—stimulate the parts of the brain that we know are responsible for fluid intelligence,” Baker says. “And these types of activities are done over and over in today’s schools, so that you would expect these students to have higher development than populations of people who had no access to schooling.”

Students must not only solve more challenging problems, they must use multiple strategies to find solutions, which adds to the mental workout in today’s schools.

Genetics and environment

For the paper, published in the journal Intelligence, researchers conducted studies from three perspectives: neurological, cognitive and demographic.

Genetics alone can’t explain the Flynn Effect, they say. Natural selection happens too slowly to be the sole reason for rising IQ scores, suggesting that intelligence is a combination of both genetics and environment.

“The best neuroscience is now arguing that brains of mammals, including, of course, humans, develop in this heavy genetic-environmental dependent way, so it’s not an either-or situation,” Baker says. “There’s a high genetic component, just like there is for athletic ability, but the environment can enhance people’s abilities up to unknown genetic limits.”


Researchers used functional Magnetic Resonance Imaging to measure brain activity in children solving certain math problems and found that problems typical of today’s schooling activated areas of the brain known as centers of fluid intelligence, for instance, mathematical problem solving.

A field study was also conducted in farming communities in Peru where education has only recently become fully accessible. The survey showed that schooling was a significant influence on improved cognitive functioning.

To measure the challenge level of lessons, 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.

Other researchers from Penn State; Ohio State University; Oregon Health & Science University, and Group for Analysis of Development of Lima, Peru contributed to the study.

The National Science Foundation supported this work.

Source: Penn State