My question seems to be a bit bizarre to say the least, but two new studies do shed some new light on what influences IQ.
The first study looks at parental influences on the development of verbal intelligence, and does this by looking at children who have been adopted to control for genetic confounding. And what’s the verdict? Parenting has a marginal and inconsistent influence on offspring IQ
In short they conducted 3 studies:
- Study 1 examined academic numeracy tasks and prefrontal cortex activation among 8–19 year-olds.
- Study 2 examined variable exposure to schooling and cognitive executive functioning among subsistence-level farmers.
- Study 3 examined the cognitive demand of primary school mathematics textbooks over the 20th century.
Their findings suggest that mass education is one cause of the Flynn Effect.
From the press release:
School enrollment in the United States reached almost 90 percent by 1960. However, the researchers, who report their findings in the current issue of Intelligence, suggest that it is not just increasing attendance, but also the more challenging learning environment that are reasons behind the IQ score rise.
“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,” said 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. This is what our neurological and cognitive research shows.”
He added that over the century, as as a higher percentage of children from each new generation went to school and attended for more years, this produced rising IQ scores.
“Even after full enrollments were achieved in the U.S. by about the 1960s, school continued to intensify its influence on thinking,” said Baker.
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, Baker said.
“Many like to think that schooling has become ‘dumbed down,’ but this is not true,” said Baker. “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, he added, 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,” said Baker. “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, according to Baker.
The researchers conducted three studies, from neurological, cognitive and demographic perspectives, according to Baker.
He said that genetics alone could not explain the Flynn Effect. Natural selection happens too slowly to be the sole reason for rising IQ scores. This suggests that intelligence is a combination of both genetics and environment.
(Note by me: so this nuances also a bit the first study I mentioned)
“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,” said Baker. “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.”
In the first study, the researchers used functional Magnetic Resonance Imaging to measure brain activity in children solving certain math problems. They 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, the 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.
Abstract of the first study by Beaver et al.:
The association between family/parenting and offspring IQ remains the matter of debate because of threats related to genetic confounding. The current study is designed to shed some light on this association by examining the influence of parenting influences on adolescent and young adult IQ scores. To do so, a nationally representative sample of youth is analyzed along with a sample of adoptees. The sample of adoptees is able to more fully control for genetic confounding. The results of the study revealed that there is only a marginal and inconsistent influence of parenting on offspring IQ in adolescence and young adulthood. These weak associations were detected in both the nationally representative sample and the adoptee subsample. Sensitivity analyses that focused only on monozygotic twins also revealed no consistent associations between parenting/family measures and verbal intelligence. Taken together, the results of these statistical models indicate that family and parenting characteristics are not significant contributors to variation in IQ scores. The implications of this study are discussed in relation to research examining the effects of family/parenting on offspring IQ scores.
Abstract of the second study by Barker et al.:
The phenomenon of rising IQ scores in high-income nations over the 20th century, known as the Flynn Effect, indicates historical increase in mental abilities related to planning, organization, working memory, integration of experience, spatial reasoning, unique problem-solving, and skills for goal-directed behaviors. Given prior research on the impact of formal education on IQ, a three-tiered hypothesis positing that schooling, and its expansion and intensification over the education revolution, is one likely cause of the Flynn Effect is tested in three studies. First, a neuroimaging experiment with children finds that neuromaturation is shaped by common activities in school, such as numeracy, and share a common neural substrate with fluid IQ abilities. Second, a field study with adults from insolated agrarian communities finds that variable exposure to schooling is associated with related variation in the mental abilities. Third, a historical–institutional analysis of the cognitive requirements of American mathematics curriculum finds a growing cognitive demand for birth cohorts from later in the 20th century. These findings suggest a consilience of evidence about the impact of mass education on the Flynn Effect and are discussed in light of the g-factor paradigm, cognition, and the Bell Curve debate.