How Are Extremely Intelligent Kids at a Young Age Different from Others: Genetics or More?

From the moment of conception, we are subjected to a myriad of influences that shape who we become. Our brains, both physical and conceptual, play a significant role in determining our intelligence and other cognitive abilities. This article delves into the differences between extremely intelligent children, such as those who understand college-level subjects by age 10 or less, and their less gifted counterparts, exploring whether these differences are primarily genetic or if other factors come into play.

Genetics and Heritability

Intelligence is, indeed, primarily a product of our genes. Studies have shown that in adults, about 85% of the variance in IQ is attributed to genetic factors. However, this percentage is lower in young children, at around 40%, and increases as they grow older, reaching up to 85% by adulthood. This phenomenon is known as the Wilson effect, indicating a strong genetic influence on intelligence as cognitive development matures.

Researchers often use the notations A, C, and E to describe heritability:

A Additive Polygenic: Represents the influence of multiple genes. C Shared Environment: Factors shared within a family, such as parenting style. E Nonshared Environment: Unique experiences that make individuals different from each other.

While shared environmental factors (C) can play a role, the nonshared environment (E) becomes less significant as the genetic expression continues to increase, making genetic factors more dominant as children grow older.

Brain Differences Between Intelligent and Less Intelligent Children

Intelligent children often exhibit different brain structures and functions compared to those with average intelligence. A few key differences and their implications are discussed below:

Brain Volume and Cortex Size

Brain volume is positively correlated with IQ, with a correlation coefficient of around 0.40. This correlation has been attributed to having a lower neurite density, allowing neurons to form more efficient connections. The correlation increases when considering the sum of the 14 Brodmann Areas that relate to general intelligence (g), reaching up to 0.70 in some studies.

The cortex size also correlates positively with intelligence. The average thickness of the cortex, which estimates the length of cortical columns, is positively correlated with IQ. This measurement has even been patented as a method to estimate intelligence.

Cortical Surface Area and Myelination

The surface area of the cortex, used as a representation of the number of cortical columns in a given brain, also correlates positively with IQ. Demyelination, or the loss of the myelin sheath, can severely affect cognitive performance, as myelin significantly speeds up neurological signal transmission.

Brain Networks and Connectivity

The connectivity of brain networks, particularly those connecting to hubs known as "rich clubs," is positively correlated with IQ. Studies using diffusion tensor imaging and functional MRI have shown that a shorter mean path length in these networks is associated with higher intelligence. This structure is similar to the way data is transmitted on the internet.

Corpus Callosum and Tissue Integrity

The corpus callosum plays a crucial role in communication between the hemispheres. Curiously, a higher curvature of the corpus callosum is associated with higher IQ, a trait that females are more likely to have. Additionally, MRI-based measures of tissue integrity, such as fractional anisotropy (FA), correlate with intelligence levels. Higher FA suggests better tissue integrity and less diffusivity, indicating higher intelligence.

Glucose Uptake Efficiency

An early study by Richard Haier showed that bright brains consume less glucose while performing a task compared to duller brains. This finding suggests that higher efficiency is linked to higher intelligence.

Glial Cell Density

Glial cells, once thought of merely as glue, have recently been found to play a vital role in information transfer. Einstein's brain, for example, had a higher fraction of glial cells compared to the average brain. This further emphasizes the complexity of neurobiological factors contributing to intelligence.

Conclusion

While genetics undoubtedly play a substantial role in determining intelligence, the multifaceted nature of neurological intelligence indicates that a combination of genetic and environmental factors contribute to this trait. The intricate connections and unique structures of the brain in extremely intelligent individuals highlight the importance of understanding both genetic and experiential influences in cognitive development.

Further research and exploration in this field can provide valuable insights into the mechanisms of intelligence and help tailor educational and therapeutic interventions to enhance cognitive abilities.