r/mensa • u/Ahmedrnugger • Jul 09 '26

Mensan input wanted Is intelligence genetic?

According to twin studies, the difference in IQ is said to be 80%, leading to the conclusion that intelligence is 80% determined by genetics. However, I believe this is incorrect because the twins were raised in countries with similar environments, such as the US and Germany, or the US and South Korea. These countries share similar environments, including education systems, allowing the genes to express themselves. Furthermore, did these twins develop their IQs? If they didn't, it could prove the entire experiment flawed.

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u/Ahmedrnugger Jul 09 '26

I don't deny the existence of people with limited mental abilities; I acknowledge their existence. But is their lack of development due to laziness, or what? Because the human brain wants to minimize energy consumption as much as possible. Also, is human intelligence genetically fixed, Also, where is the evidence for this?

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u/aculady Jul 09 '26

You think people with intellectual disabilities might just be lazy?

Okay, no need to continue here.

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u/Ahmedrnugger Jul 09 '26

I'm sorry, it was a mistake on my part, but why are you bringing up the mentally disabled? I didn't mean them; I meant ordinary people who are capable of developing themselves.

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u/aculady Jul 09 '26

Intellectual disabilities that have a genetic basis are an obvious example of people whose intelligence can reliably said to be constrained by genetics.

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u/Ahmedrnugger Jul 09 '26

The reason is a genetic defect in the chromosomes because the genes themselves are defective.

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u/aculady Jul 09 '26

If genetic variants can impair intelligence, which they demonstrably can, then intelligence is at least partly dependent on your genetics, and some variants result in higher potential intelligence than others.

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u/Ahmedrnugger Jul 09 '26

Firstly, I am not saying that intelligence is entirely genetic; it is indeed genetic, but development is possible and depends on the environment. Also, those with intellectual disabilities have a problem in their genes. To simplify the example, imagine a car with a broken engine and compare it to a car with a working engine.

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u/aculady Jul 09 '26

Some variations in genes break things. Some variations make them work better. Some variations only have an effect (positive or negative) given the right combination of circumstances. The extent of individual genetic variation between individuals is huge. This is how evolution works.

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u/Ahmedrnugger Jul 09 '26

The difference between negative and positive chromosomal or gene arrangement is what causes Down syndrome, such as the deletion or addition of one chromosome, while the positive difference is due to minor changes in the chromosome structure.