Genetic and Environmental Influences on Intelligence

Genetic and Environmental Influences on Intelligence Theories Cognitive Psychology Print 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 policy Kendra Cherry Updated on October 07, 2019 Michael H / Digital Vision / Getty Images More in Theories Cognitive Psychology Behavioral Psychology Developmental Psychology Personality Psychology Social Psychology Biological Psychology Psychosocial Psychology 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 importantâ€"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 between 40 and 80% of 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 IQs are more similar than those of fraternal twins (Plomin Spinath, 2004).Siblings reared together in the same home have IQs that are more similar than those of adopted children raised together in the same environment (McGue others, 1993). 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 Identical twins reared apart have IQs that are less similar than identical twins reared in the same environment (McGue others, 1993).School attendance has an impact on IQ scores (Ceci, 2001).Children who are breastfed during the first three to five months of life score higher on IQ tests at age 6 than same-age children who were not breastfed (Kramer others, 2008). So what are some of the environmental influences that can account for variances in intelligence? Factors such as family, education, enriched social environments, and peer groups have all been linked to differences in IQ. 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?