Theories Cognitive Psychology Genetic and Environmental Influences on Intelligence By Kendra Cherry facebook twitter Kendra Cherry, MS, is an author, educational consultant, and speaker focused on helping students learn about psychology. Learn about our editorial process Kendra Cherry Updated on September 17, 2020 Print Michael H / Digital Vision / Getty Images 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? 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. One important thing to note about the genetics of intelligence is that it is not controlled by a single "intelligence gene." Instead, it is the result of complex interactions between many genes. Next, it is important to note that genetics and the environment interact to determine exactly how inherited genes are expressed. For example, if a person has tall parents, it is likely that the individual will also grow to be tall. However, the exact height the person reaches can be influenced by environmental factors such as nutrition and disease. A child may be born with genes for brightness, but if that child grows up in a deprived environment where he is malnourished and lacks access to educational opportunities, he may not score well on measures of IQ. Evidence of Genetic Influences on Intelligence Twin studies suggest that identical twins IQ's are more similar than those of fraternal twins.Siblings reared together in the same home have IQ's that are more similar than those of adopted children raised together in the same environment. In addition to inherited characteristics, other biological factors such as maternal age, prenatal exposure to harmful substances, and prenatal malnutrition may also influence intelligence. Studies have found that people with lower intelligence are more likely to report criminal victimization, which can have serious consequences including physical injury, loss of property, and psychological and emotional trauma. Evidence of Environmental Influences on Intelligence Identical twins reared apart have IQ's that are less similar than identical twins reared in the same environment.School attendance has an impact on IQ scores Children who breastfed for 12 months or longer had a higher IQ (about 3.7 points) at age 30. So what are some of the environmental influences that can account for variances in intelligence? For 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 more attention from parents. Research also suggests that parents expect older children to perform better on a variety of tasks, whereas later-born siblings face lesser task-focused expectations. Is Your IQ Score Above Average? Was this page helpful? Thanks for your feedback! Ever wonder what your personality type means? Sign up to find out more in our Healthy Mind newsletter. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to 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.2017.104 Zheng Y, Rijsdijk F, Arden R. Differential environmental influences on the development of cognitive abilities during childhood. Lancet Infect Dis. 2020;20(7):e148. doi:10.1016/j.intell.2017.11.005 Haworth CM, Dale P, Plomin R. A Twin Study into the Genetic and Environmental Influences on Academic Performance in Science in nine-year-old Boys and Girls. Int J Sci Educ. 2008;30(8):1003. doi:10.1080/09500690701324190 Segal NL, Mcguire SA, Havlena J, Gill P, Hershberger SL. Intellectual similarity of virtual twin pairs: Developmental trends. Pers Individ Dif. 2007;42(7):1209-1219. doi:10.1016/j.paid.2006.09.028 Boutwell B, Connolly E, Barbaro N, et. al. On the genetic and environmental reasons why intelligence correlates with criminal victimization. Lancet Infect Dis. 2020;20(7):e148. doi:10.1016/j.intell.2017.04.003 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 B, Hartwig F, Victora C. Breastfeeding and intelligence in adulthood: due to genetic confounding? The Lancet. 6(12), 1276-1277. doi:10.1016/S2214-109X(18)30371-1 Lehmann J, Nuevo-Chiquero A, Vidal-Fernandez M. The Early Origins of Birth Order Differences in Children’s Outcomes and Parental Behavior. The Journal of Human Resources. 53(1), 123-156. doi:10.3368/jhr.53.1.0816-8177 Additional Reading Ceci, S. (2001). Intelligence: The Surprising Truth. Psychology Today, 34(4), 46. Kramer, M.S., About, F., Mironeva, E., Vanilovich, I., Platt, R.W., Matush, L., Shapiro, S. (2008). Archives of General Psychiatry, 65(5), 578-584. doi: 10.1001/archpsyc.65.5.578. Plomin, R., & Spinath, F. M. (2004). Intelligence: Genetics, Genes, and Genomics. Journal of Personality and Social Psychology, 86(1), 112–129. McGrue, M., Bouchard, T.J., Iacono, W.G., & Lykken, D.T. (1993). Behavioral Genetics of Cognitive Ability: A Life-Span Perspective. In R. Plomin & G.E. McClearn (Eds.), Nature, Nurture, and Psychology. Washington, DC: American Psychological Association.