Nature vs Nurture: How Our Genes and Environment Shape Our IQ

Human intelligence is a complex thing and researchers try to understand it. Psychologists investigated it considering two principal perspectives - nature and nurture - and learned that both influenced our intelligence.

Nature vs. Nurture in Determining IQ

Intelligence can be defined in a variety of ways, which makes it difficult to assess. The intelligence quotient (IQ) is a commonly used intelligence metric in research. According to studies, both nature and nurture contribute to our intelligence. Nature includes all genetic factors influencing our intelligence, while nurture refers to the environmental factors.

Numerous studies have examined IQ parallels and variances within families, emphasizing twins and adopted children in particular. In order to ascertain whether any particular regions of the genome are connected to IQ, other research has looked at variances throughout the full genomes of numerous individuals (a technique known as genome-wide association studies, or GWAS).

Research has indicated a hereditary component to IQ, but no single gene has been definitively linked to significant variations in intellect. It is possible that a person's intellect is influenced by a large number of genes, each of which has a negligible effect. Additional genetic factors play a role in other aspects of intelligence, such as verbal ability and memory.

The environment also has a significant impact on intelligence. Throughout a child's growth, their upbringing and family environment, their schooling and access to resources, their health and diet, and their education all have a role in determining their intelligence.

Indeed, genes and environment impact an individual. While it's not easy to determine which factors are from the genes or the environment, it is evident that intelligence is influenced by a combination of both.

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Genes and Environment on IQ

Other studies followed identical, fraternal twins and triplets who had been separated at an early age. The research considered their strikingly different environment in assessing their intelligence.

"A strict dichotomy between genes and environment is no longer relevant; they work in concert," said Nancy Segal, a psychologist at California State University, Fullerton. Segal, herself is a fraternal twin, and she has made a career in studying twins. She also penned the 2012 book "Born Together - Reared Apart: The Landmark Minnesota Twins Study."

Numerous studies involving thousands of identical and fraternal twin pairs, raised separately and together, have allowed researchers to evaluate the relative contributions of environment and genes to a wide range of traits.

According to Dr. Segal, "it's trait-specific," with varying ratios depending on the attribute in question. While they can't estimate the contribution of genes and environment in an individual, they can do so on a population basis.

Based on the reared-apart twins studies, on average, half of the variances in personality and religion are inherited; yet, for a feature like intelligence quotient, roughly 75% of the variation is inherited, with just 25% from the environment.