How do twin studies support the view that intelligence is inherited?
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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. Show
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
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
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. 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.
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Kendra Cherry Thanks for your feedback! What do twin studies say about intelligence?Early twin studies of adult individuals have found a heritability of IQ between 57% and 73%, with some recent studies showing heritability for IQ as high as 80%. IQ goes from being weakly correlated with genetics for children, to being strongly correlated with genetics for late teens and adults.
Why are twin studies helpful in studying intelligence?Twin studies allow disentanglement of the shared genetic and environmental factors for the trait of interest. Researchers can estimate the proportion of variance in a trait attributable to genetic variation versus the proportion that is due to shared environment or unshared environment.
What can twin studies tell us about heritability?Researchers use this method, and variations on it, to estimate the heritability of traits: The percentage of variance in a population due to genes. Modern twin studies also try to quantify the effect of a person's shared environment (family) and unique environment (the individual events that shape a life) on a trait.
What role does genetics play in twin intelligence studies?Numerous studies on twins suggest that between 40 and 80 percent of the variance in IQ is linked to genetics, suggesting that genetics may play a larger role than environmental factors in determining an individual's IQ.
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