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Intelligence: Nature or Nurture?

You must have a friend who seems to never study hard but always gets good grades. While you are wondering how they do that, you must have thought maybe they were born intelligent, or maybe they have ‘genius genes’. But, is that true? Is intelligence inherited from genes? Or does the environment have something to do with intelligence? This topic has been a hot debate in psychology from time to time.

According to twin studies, genetics is  the main factor of individual differences in cognitive abilities, followed by shared environment (factors that cause family members to be similar) and non-shared environment (factors that distinguish family members).

Twins who are identical have more similar IQ than fraternal twins, and siblings who were raised together in the same house have more similar IQ than adopted children who grew up in the same household. These are proof that IQ is affected by genetics. But, the IQ of identical twins who were raised apart are less similar than those who were raised in the same environment, proving that the environment also affects IQ.

Furthermore, pregnancy and childhood are the most crucial time to the development of one’s intelligence. Nutrition needed during pregnancy and early childhood development together with exposure to pollutants can affect intelligence. There is a possibility for the environment to affect our brain’s development when we were children because at that time our brain is still growing. However, our brain will reach its peak by the time we become adults, so the environment can no longer influence it significantly.

To conclude, both nature and nurture influence human intelligence. Even though genetics is the major factor of an individual IQ, environmental factors such as prenatal condition, nutrition, surrounding environment, and disease can also affect it.

So, those explanations will answer your curiosity about your friend who always gets good grades even though they don’t seem to study hard. Well, they might have been born with good genes, or they may also have grown up in a good environment and consumed adequate nutrition when they were younger. If not, they are secretly studying when you don’t see them.


Cherry, Kendra. “Genetic and Environmental Influences on Intelligence.” Verywell Mind, 26 August 2021, Accessed 7 March 2022.

Oommen, Arun. “Factors Influencing Intelligence Quotient.” MedCrave, 25 August 2014, Accessed 7 March 2022.

Zhang, Yao, et al. “Differential environmental influences on the development of cognitive abilities during childhood.” Intelligence, vol. 66, 2018, pp. 72-78. Differential environmental influences on the development of cognitive abilities during childhood,

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