Is Intelligence Hereditary?

Is intelligence hereditary?

Check out this answer from Consensus:

Intelligence is a highly heritable trait influenced by a complex interplay of genetic and environmental factors. While genetic research has made significant strides in identifying the heritable components of intelligence, environmental influences and gene-environment interactions remain crucial in shaping cognitive abilities. Understanding the genetic basis of intelligence and its interaction with the environment holds promise for enhancing educational and social outcomes.

The question of whether intelligence is hereditary has intrigued scientists for decades. Intelligence, defined as the ability to learn, reason, and solve problems, is a complex trait influenced by both genetic and environmental factors. Recent advancements in genetic research have provided significant insights into the heritability of intelligence, revealing the intricate interplay between genes and the environment.

Genetic Basis of Intelligence

Numerous studies have established that intelligence is highly heritable. For instance, genome-wide association studies (GWAS) have identified inherited genome sequence differences that account for approximately 20% of the 50% heritability of intelligence1. This suggests that a substantial portion of intelligence can be attributed to genetic factors.

Twin studies have been instrumental in understanding the heritability of intelligence. Research indicates that the heritability of intelligence increases from about 20% in infancy to as much as 80% in later adulthood3. This increase in heritability over the lifespan underscores the significant role of genetics in shaping cognitive abilities.

Environmental Influences and Gene-Environment Interactions

While genetics play a crucial role, environmental factors also significantly impact intelligence. The interaction between genes and the environment, known as Gene × Socioeconomic Status (SES) interaction, has been a focal point of research. Studies have shown that genetic influences on intelligence are more fully realized under conditions of socioeconomic advantage, whereas they are suppressed under conditions of socioeconomic privation4. This highlights the importance of providing supportive environments to maximize genetic potential.

Maternal Effects and Shared Environments

The role of maternal effects and shared environments in the heritability of intelligence has also been explored. A meta-analysis of 212 studies revealed that maternal effects account for 20% of the covariance between twins and 5% between siblings, suggesting that the shared maternal environment significantly influences intelligence2. This finding challenges the traditional view that family environments are the primary shared environmental factor affecting intelligence.

Genetic Correlations with Other Traits

Intelligence is not only heritable but also genetically correlated with other traits. For example, genetic studies have shown that intelligence captures genetic effects on diverse cognitive and learning abilities, which correlate phenotypically and genetically3. Additionally, there is evidence of genetic correlations between intelligence and brain structure, indicating that genetic influences on brain morphology partly mediate cognitive abilities10.

Advances in Genetic Research

The advent of the Human Genome Project and subsequent advancements in genomic technologies have revolutionized the study of intelligence. Researchers are now able to identify specific genes responsible for the heritability of intelligence and understand the brain pathways between genes and cognitive functions6. These developments have paved the way for functional genomics, which aims to elucidate the biological mechanisms underlying intelligence.

Is intelligence hereditary?

Dimitri van der Linden has answered Near Certain

An expert from Erasmus University Rotterdam in Psychology

There is a tremendous amount of empirical research clearly showing that intelligence is hereditary. The estimates range somewhere between .50 to .80 (and are likely closer towards the latter). Obviously, each line of research on this topic (e.g., twin studies, adoption studies, GWAS) has its own specific limitations. Yet, despite such limitations, the different lines of research converge on the conclusion that intelligence is heritable.

The type of evidence comes from many directions. Just to name a few prominent ones:

1) Twin studies that distinguish between genetic and environmental aspects show a substantial heritable component.

2) Adoption studies show that the intelligence of the adopted child more strongly resembles the intelligence of the biological parents than the adoption parents.

3) The heriability coefficient of intelligence actually increases with increasing age. Which would not be expected if it is mainly the environment that would have the strongest influence.

There still may be some debate about the exact estimate of the heritability coefficient (for example, whether it is more closely to 60 or to 80%). But, based on the available evidence that has been collected during the last hundred fifty year or so, I don’t think that there can be much doubt that intelligence is quite strongly heritable.

Is intelligence hereditary?

Thomas J Bouchard Jr has answered Near Certain

An expert from University of Minnesota in Psychology, Neuropsychology

The term hereditary in this context is ambiguous. A more precise question with regard to intelligence is; “Is variation in intelligence influenced by genes?” The answer is yes, but the degree of influence (heritability) depends on age.

Genetic influence on intelligence in young children is much less than in adults. In the past genetic influence had been confirmed using twin and adoption studies (kinship studies). Current research using methods that analyze DNA (Genome Wide Association Studies or GWAS) also confirm genetic influence on intelligence. These new studies have not yet demonstrated as high a degree of genetic influence as the kinship studies. This is true for other traits such as height as well. This is work in progress. The heritability of IQ in adulthood estimated by kinship studies is in the range .70 to .80.

Bouchard, T. J., Jr. (2013). The Wilson Effect: The increase in heritability of IQ with age. Twin Research and Human Genetics, 16, 923-930. doi:10.1017/thg.2013.54

Is intelligence hereditary?

Nicholas J Grahame has answered Near Certain

An expert from Indiana University ? Purdue University Indianapolis in Psychology, Genetics

Intelligence is heritable, even more so than features like height and weight. Adoption and twin studies offer the best evidence of this. Children adopted at very young ages resemble their adoptive parents in terms of IQ test scores when they are children (i.e., age 5 and younger). As they grow older, though, they increasingly resemble their biological parents. By the time these children are 16 or so, about 70 to 80% of the differences among individuals can be chalked up to their biological parents’ genes, rather than the environment in which they were raised. In other words, if you want to know what a person’s IQ will be, look to the IQ of the biological parents rather than the adoptive parents. These kinds of studies show compellingly how important our genes are in determining our intelligence.

Is intelligence hereditary?

Michelle Luciano has answered Near Certain

An expert from Edinburgh University in Psychology

Twin studies and genome wide studies show that intelligence as measured by psychometric tests is around 50% heritable.