Is Intelligence Inherited? The Heritability of IQ Explained

The heritability of IQ has always been a much-debated topic among psychologists, who couldn’t settle on whether intelligence is inherited or acquired. Some schools of thought prioritize genetics, while others advocate for environmental factors playing a more significant role.

However, the latest research demonstrates that both are true—a variety of factors work together to determine intelligence. In this article, we will delve deeper into them, with an emphasis on genetics.

So, let’s dive in.

Key Takeaways

• A large part of intelligence is inherited from parents. However, that doesn’t mean children will have exactly the same IQs as their mothers and fathers.
• Intelligence is too complex to be influenced by only one factor: thousands of genes, the environment, education, and nutrition all play an important role.
• Even if you’re born into a low-IQ family, you can inherit a combination of genes that results in a high IQ.
• Chromosomal and genetic mutations are frequently the cause of intellectual disabilities, although brain damage and malnutrition can also impair cognition.

Genetic Intelligence: Definition

Is intelligence inherited from genetics?

Genetic intelligence is intellectual potential that stems from the genetic makeup inherited from our parents. In other words, it’s our natural, innate cognitive potential that is present even before environmental factors come into play.

Although scientists have been trying to isolate specific genes responsible for intelligence, that has proved to be a difficult task. In fact, the largest studies indicate that intelligence is a highly polygenic trait, with over 1,000 genes associated with cognitive ability.

On their own, most of these genes have a very small effect on overall intelligence. However, their joint effect during various stages of brain development can have significant implications for cognition and mental ability.

Is Intelligence Inherited?

Intelligence is largely inherited—according to numerous studies conducted on twins, 50–80% of a child’s IQ depends on the parents’ intelligence level.

However, there is some debate on which parent’s genes play a more significant role in determining the child’s IQ.

Many online sources claim intelligence is inherited from the mothers, as the so-called “intelligence genes” are carried over on the X chromosome. Since women have two of those, while men have only one, this conclusion may not seem entirely far-fetched.

But even if we accept the premise that intelligence genes come exclusively from the X chromosome, that would only mean that boys inherit IQ from their mothers. Girls get one X chromosome from each parent, so their intelligence would still depend on both parents.

That said, intelligence isn’t as straightforward as that. As mentioned before, there are thousands of genes that determine intelligence in addition to non-negligible environmental factors. Therefore, it’s impossible to make sweeping statements about the heritability of intelligence without further research.

Key Factors That Influence Intelligence

Key factors that influence intelligence aside from genetics include the environment, education, and nutrition, particularly during the developmental years.

Below, we explore their role in determining intelligence in more detail.

#1. Environment

Windmills in the nature

Even if a child has enormous IQ potential, they may not be able to realize it without the environment’s support. In other words, if parents and relatives do nothing to nurture their intelligence, their IQ will likely stagnate.

On the other hand, the case of Judit Polgar, a Hungarian chess grandmaster, proves that intelligence can be nurtured from a young age. Polgar might have been gifted from the start, but she likely wouldn’t have reached the same heights if her father hadn’t set out to create a genius.

For a deeper dive into the relationship between chess and IQ, check out our article on whether chess can actually increase IQ.

#2. Education

Is intelligence inherited in education?

Proper education boosts both fundamental aspects of general intelligence—fluid and crystallized intelligence—and develops IQ in the process.

This phenomenon was observed and dubbed the Flynn effect, which refers to the steady increase in IQ since testing first began. Experts believe compulsory education is the largest contributor to this phenomenon, as it develops students’ innate abilities and teaches them how to think and solve problems.

#3. Nutrition

Healthy vegetables and fruits

Like any other organ, your brain needs nutrients to develop and function properly. When it doesn’t have enough, it focuses on survival rather than cognition and its various aspects. As a result, lower average IQs have been observed in countries that struggle with food shortages and poverty.

Does Low IQ Run in Families?

Low IQ does run in families since genetics play a significant role in determining intelligence.

However, as we’ve seen above, biological factors don’t affect intelligence alone. Even a child from a family with low IQ can develop their intelligence by getting a proper education, being raised to value intellectual pursuits, and receiving enough support from their environment.

Moreover, considering the number of genes that determine intelligence, it’s possible to inherit a combination that results in an average or relatively high IQ. This would explain why geniuses are sometimes born into seemingly regular families.

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What Is a Genetic IQ Disability?

A genetic IQ disability is a condition described as having an IQ under 70. This can significantly impair a person’s ability to learn, communicate, and perform everyday tasks.

Usually, this type of disability stems from genetic mutations or chromosomal abnormalities, like in the case of Down’s syndrome, which is caused by an extra copy of chromosome 21.

However, intellectual disabilities can result from various other factors, such as the child’s exposure to alcohol in the womb, premature birth, and other problems during pregnancy and childbirth.

Check out our article on alcohol and IQ to dive deeper into this topic.

In addition, IQ can still experience drops even after birth. Brain injuries, iodine deficiency, malnutrition, and infectious diseases can affect IQ, especially during the developmental period.

Final Thoughts

So, is intelligence genetic or environmental? Science suggests that it’s a bit of both, as environmental factors play almost as crucial a role in its development as genetic ones.

In other words, although your genetic makeup will largely determine how much your cognitive abilities can develop, your environment and lifestyle will determine whether you will reach your full potential.

So, seek opportunities for self-development and watch your intelligence improve!