Intelligent Brain
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Intelligence and the heritability problem


One of the most questionable developments that I have seen in recent years is that scientific research gets constantly dismissed as being insignificant if it doesn’t support one’s world view. Many uncomfortable scientific findings just get dismissed by society or mainstream media as false. One of them is the question of whether intelligence is inheritable or not.

I was enraged when I saw an article by the reputable German newspaper “Süddeutsche” which claims in its introduction that:

“Intelligenz ist nicht Angeboren: Forscher behaupten immer wieder das Gegenteil. Richtig aber ist: Die Gene haben kaum einen Effekt – es kommt auf die Förderung an.”

“Intelligence is not innate: Researchers claim the opposite again and again. But the truth is: The genes have hardly any effect – it depends on social support.”

So if the majority of researchers claim that intelligence is highly heritable, why must it be wrong then? Just because the psychologist who wrote this article thinks that it discourages less gifted people from achieving success in academia, that doesn’t mean we should ignore the problem and not talk about it.

What is intelligence?

Intelligence is indeed a complex trait that is influenced by both genetic and environmental factors. Most often intelligence is defined as the ability to learn from experiences and to adapt to changing environments. Intelligence has nothing to with how well we are able to reproduce facts.

intelligence depends on many disciplines.
Intelligence is multifactorial.

Being intelligent means to have the ability to:

  • reason
  • plan
  • solve problems
  • think abstractly
  • understand complex ideas

The scientific consensus nowadays is that genetic factors underlie about 50 percent of the difference in intelligence among individuals. The other 50 percent is due to environmental factors like, for example:

  • child’s home environment and parenting
  • education
  • availability of learning resources
  • nutrition

Scientists distinguish two types of intelligence: crystallized and fluid intelligence.

Fluid intelligence is the ability to solve new problems, use logic in new situations, and to identify patterns. Crystallized intelligence, on the other hand, is the ability to use learned knowledge and experience.

While crystallized intelligence can grow over the entire course of life, fluid intelligence is highly heritable and starts to decline in 20-year-olds already.

Both types of intelligence are evenly important. Our crystallized intelligence grows through education and academia. It is also possible to improve our fluid intelligence, although that is a much harder task because you cannot “learn” fluid intelligence by repetition and experience. Fluid intelligence is about solving new and unknown problems with novel thinking patterns. This is something that our education system has a hard time conveying.

Our education system focuses on improving crystallized intelligence

Our approach to education is: Learn and improve by experience and exposure. You learn in school and academia to solve new problems by relying on previous experiences and extensive background knowledge. Needless to say, experts are often not the best people to solve problems in their niche. They tend to overthink problems and rely too heavily on their experience.

boy in school studying a book
In school, we typically learn through exposure to improve our crystalline intelligence.

Sometimes, a person completely unfamiliar with a topic can solve a problem better than the experts. Because the person unfamiliar with the topic has no experience to rely on. Therefore, this person thinks openly without prejudice and bias about the topic and isn’t afraid to suggest unconventional solutions. To have this ability to solve completely unfamiliar problems is a sign that this person has high fluid intelligence which can make up for a lack of experience.

An overdose of crystallized knowledge is often harmful. Because the more knowledge we have to rely on, the less we tend to think in unconventional ways. We don’t seek out new or unconventional solutions if someone has previously shown us how to solve a problem efficiently.

Yet, our school system favors the growth of crystallized intelligence because it is mainly determined by the environment and thus can be trained. Students with low fluid intelligence get trained in solving problems through experience rather than through logical and innovative thinking.

But the success of our society heavily relies on innovative and unconventional thinkers. People who can solve complex problems without relying on experience. People who have visions of things that can’t exist. These are the people that will invent new technologies and solve scientific problems.

A controversial theory

The Stanford developmental biologist Gerald Crabtree suggests that humanity is getting dumber every year. In his eyes, an average citizen of ancient Greece was probably smarter than the average person nowadays.

According to Crabtree, intelligence was reduced as we began to live in supportive societies. Community life reduced the selective pressure placed on every individual so that there was suddenly a chance for anyone to survive. Nowadays, you don’t have to die young if you get born disabled or dumb.

Ancient greek people statue
It’s a controversial theory that the ancient Greeks were, on average, smarter than we are today.

However, this lack of natural selection also accelerates the accumulation of genetic mutations that have a deleterious effect on intellect and emotional stability. If two parents with low intelligence have a child, then that child has a high probability of being dumb too. It will be able to acquire a large amount of crystallized knowledge, however, it will probably lack highly inheritable fluid intelligence.

The genes are a limiting factor. No matter how much crystallized knowledge the child acquires in life, it will still pass on his deleterious genes to its children.

This is not necessarily a bad thing. I am happy to live in a society where there is no selective pressure based on intelligence to survive. However, we should be aware that not everyone gets born as a little Einstein.

The German school system is developing in the wrong direction

Nevertheless, the German state ministers of education continue to push forward their agenda of integrated comprehensive schools. For a long time, Germany used to have a successful education system where students were divided after 4th grade among 3 types of secondary schools depending on their intelligence and performance.

However, nowadays, the most advanced type of secondary school has been massively downgraded to become the school of the masses. Besides that, many new integrated comprehensive schools have been founded, although they only receive little tolerance from the masses. Nowadays, whoever wants a solid secondary education for his kids needs to send them to the most advanced secondary school.

However, no one profits from such a system. Not only are teachers overstretched if they have to cater to very intelligent and not so intelligent students at once. Intelligent students will also not receive the opportunity to sharpen and develop their fluid intelligence. The not-so-intelligent students, on the other hand, become frustrated over time because they are always the worst at anything.

school boy bored in school
Not all students are gifted evenly.

Way too often we assume that anyone has the same potential, the same abilities and that everyone can achieve anything by pure willpower and discipline. But that is not the case. There will always be kids who are naturally more gifted than others. You cannot deny that and offer the same level of education to anyone. In such a system, everyone loses.

We need more specialized offers that focus on specific target groups. The goal cannot be to collectively treat everyone the same. Yet that is what many pedagogues dream of. We need to let go of idealistic thought processes and start to look at things from a realistic point of view. Even if it hurts from a humane point of view.


Intelligenz ist nicht angeboren

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