Genetic and Environmental Influences on Intelligence

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What role do genetic and environmental influences play in determining intelligence? This question has been one of the most controversial topics throughout the history of psychology and remains a hot topic of debate to this day.

In addition to disagreements about the basic nature of intelligence, psychologists have spent a great amount of time and energy debating the various influences on individual intelligence. The debate focuses on one of the major questions in psychology: Which is more important—nature or nurture?

What is intelligence?

Do Genetics or Intelligence Play a Bigger Role in Determining Intelligence?

Today, psychologists recognize that both genetics and the environment play a role in determining intelligence.

It now becomes a matter of determining exactly how much of an influence each factor has.

Twin studies suggest that the variance in IQ is linked to genetics. This research suggests that genetics may play a larger role than environmental factors in determining individual IQ.

A child may be born with genes for exceptional brightness, but if that child grows up in a deprived environment where they are malnourished and lack access to educational opportunities, they may not score well onmeasures of IQ.

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Evidence of Genetic Influences on Intelligence

All traits are heritable, with intelligence being one of the most researched. If genetics were the only factor to consider when predicting intelligence, we would expect identical twins to have identical IQ scores. The research shows:

In addition to inherited characteristics, other biological factors such as maternal age, prenatal exposure to harmful substances, and prenatal malnutrition may also influence intelligence.

Evidence of Environmental Influences on Intelligence

Historically, some theorists believed humans are born with ablank slate, and capable of becoming any type of person with any type of career, influence, and social status.The research shows:

In one example, studies have found that first-born children tend to have higher IQs than later-born siblings.Why? Many experts believe that this is because first-born children receive moreattentionfrom their parents. Research also suggests that parentsexpectolder children to perform better on a variety of tasks, whereas later-born siblings face less task-focused expectations.

What’s the Average IQ?

Take Away

Today, scientists agree that both genetics and environment impact the physical development of the brain and the cognitive development of the mind which ultimately determines intelligence. Our genetics may provide us with an intellectual capacity but our environment determines if we reach our potential. That being the case, both would appear to beequallyimportant.

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9 SourcesVerywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Plomin R, von Stumm S.The new genetics of intelligence.Nat Rev Genet. 2018;19(3):148-159. doi:10.1038/nrg.2017.104Zheng Y, Rijsdijk F, Arden R.Differential environmental influences on the development of cognitive abilities during childhood.Intelligence. 2018;66:72-78. doi:10.1016/j.intell.2017.11.005Plomin R, Deary IJ.Genetics and intelligence differences: Five special findings.Mol Psychiatry. 2015;20(1):98-108. doi:10.1038/mp.2014.105Pinker S.The Blank Slate: The Modern Denial of Human Nature. Penguin; 2003.Oommen A.Factors influencing intelligence quotient.JNSK. 2014;1(4). doi:10.15406/jnsk.2014.01.00023Ritchie SJ, Tucker-Drob EM.How much does education improve intelligence? A meta-analysis.Psychol Sci. 2018;29(8):1358-1369. doi:10.1177/0956797618774253Horta BL, Hartwig FP, Victora CG.Breastfeeding and intelligence in adulthood: Due to genetic confounding?The Lancet Global Health. 2018;6(12):e1276-e1277. doi:10.1016/S2214-109X(18)30371-1Isaacs EB, Gadian DG, Sabatini S, et al.The effect of early human diet on caudate volumes and IQ.Pediatr Res.2008;63(3):308-314. doi:10.1203/PDR.0b013e318163a271Lehmann J-YK, Nuevo-Chiquero A, Vidal-Fernandez M.The early origins of birth order differences in children’s outcomes and parental behavior.J Human Resources. 2018;53(1):123-156. doi:10.3368/jhr.53.1.0816-8177

9 Sources

Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Plomin R, von Stumm S.The new genetics of intelligence.Nat Rev Genet. 2018;19(3):148-159. doi:10.1038/nrg.2017.104Zheng Y, Rijsdijk F, Arden R.Differential environmental influences on the development of cognitive abilities during childhood.Intelligence. 2018;66:72-78. doi:10.1016/j.intell.2017.11.005Plomin R, Deary IJ.Genetics and intelligence differences: Five special findings.Mol Psychiatry. 2015;20(1):98-108. doi:10.1038/mp.2014.105Pinker S.The Blank Slate: The Modern Denial of Human Nature. Penguin; 2003.Oommen A.Factors influencing intelligence quotient.JNSK. 2014;1(4). doi:10.15406/jnsk.2014.01.00023Ritchie SJ, Tucker-Drob EM.How much does education improve intelligence? A meta-analysis.Psychol Sci. 2018;29(8):1358-1369. doi:10.1177/0956797618774253Horta BL, Hartwig FP, Victora CG.Breastfeeding and intelligence in adulthood: Due to genetic confounding?The Lancet Global Health. 2018;6(12):e1276-e1277. doi:10.1016/S2214-109X(18)30371-1Isaacs EB, Gadian DG, Sabatini S, et al.The effect of early human diet on caudate volumes and IQ.Pediatr Res.2008;63(3):308-314. doi:10.1203/PDR.0b013e318163a271Lehmann J-YK, Nuevo-Chiquero A, Vidal-Fernandez M.The early origins of birth order differences in children’s outcomes and parental behavior.J Human Resources. 2018;53(1):123-156. doi:10.3368/jhr.53.1.0816-8177

Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Plomin R, von Stumm S.The new genetics of intelligence.Nat Rev Genet. 2018;19(3):148-159. doi:10.1038/nrg.2017.104Zheng Y, Rijsdijk F, Arden R.Differential environmental influences on the development of cognitive abilities during childhood.Intelligence. 2018;66:72-78. doi:10.1016/j.intell.2017.11.005Plomin R, Deary IJ.Genetics and intelligence differences: Five special findings.Mol Psychiatry. 2015;20(1):98-108. doi:10.1038/mp.2014.105Pinker S.The Blank Slate: The Modern Denial of Human Nature. Penguin; 2003.Oommen A.Factors influencing intelligence quotient.JNSK. 2014;1(4). doi:10.15406/jnsk.2014.01.00023Ritchie SJ, Tucker-Drob EM.How much does education improve intelligence? A meta-analysis.Psychol Sci. 2018;29(8):1358-1369. doi:10.1177/0956797618774253Horta BL, Hartwig FP, Victora CG.Breastfeeding and intelligence in adulthood: Due to genetic confounding?The Lancet Global Health. 2018;6(12):e1276-e1277. doi:10.1016/S2214-109X(18)30371-1Isaacs EB, Gadian DG, Sabatini S, et al.The effect of early human diet on caudate volumes and IQ.Pediatr Res.2008;63(3):308-314. doi:10.1203/PDR.0b013e318163a271Lehmann J-YK, Nuevo-Chiquero A, Vidal-Fernandez M.The early origins of birth order differences in children’s outcomes and parental behavior.J Human Resources. 2018;53(1):123-156. doi:10.3368/jhr.53.1.0816-8177

Plomin R, von Stumm S.The new genetics of intelligence.Nat Rev Genet. 2018;19(3):148-159. doi:10.1038/nrg.2017.104

Zheng Y, Rijsdijk F, Arden R.Differential environmental influences on the development of cognitive abilities during childhood.Intelligence. 2018;66:72-78. doi:10.1016/j.intell.2017.11.005

Plomin R, Deary IJ.Genetics and intelligence differences: Five special findings.Mol Psychiatry. 2015;20(1):98-108. doi:10.1038/mp.2014.105

Pinker S.The Blank Slate: The Modern Denial of Human Nature. Penguin; 2003.

Oommen A.Factors influencing intelligence quotient.JNSK. 2014;1(4). doi:10.15406/jnsk.2014.01.00023

Ritchie SJ, Tucker-Drob EM.How much does education improve intelligence? A meta-analysis.Psychol Sci. 2018;29(8):1358-1369. doi:10.1177/0956797618774253

Horta BL, Hartwig FP, Victora CG.Breastfeeding and intelligence in adulthood: Due to genetic confounding?The Lancet Global Health. 2018;6(12):e1276-e1277. doi:10.1016/S2214-109X(18)30371-1

Isaacs EB, Gadian DG, Sabatini S, et al.The effect of early human diet on caudate volumes and IQ.Pediatr Res.2008;63(3):308-314. doi:10.1203/PDR.0b013e318163a271

Lehmann J-YK, Nuevo-Chiquero A, Vidal-Fernandez M.The early origins of birth order differences in children’s outcomes and parental behavior.J Human Resources. 2018;53(1):123-156. doi:10.3368/jhr.53.1.0816-8177

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