A high IQ is often associated with a large brain, but a recent metastudy suggests that this correlation is greatly overestimated. While several studies have indicated that a person’s intelligence quotient (IQ) tends to be related to their brain volume, various animals with relatively large brains do not come close to matching human cognitive abilities. Researchers at the University of Vienna have published a study in the journal Royal Society Open Science, which suggests that the relationship between intelligence and brain size is often overestimated. The team analyzed 86 studies with over 26,000 participants for their metastudy.
For over 200 years, the correlation between intelligence and brain size has been debated in the medical field. Some scientists believe that a larger brain can process information faster and more complexly, thereby enabling higher cognitive performance. Additionally, there are theories that suggest a higher brain volume allows seniors to better compensate for cognitive decline. However, the researchers note that a combination of brain measurement using magnetic resonance imaging (MRI) and validated intelligence tests is necessary to investigate these theories in detail. While there have been studies that have analyzed this data, their results often differ greatly due to various study designs, statistical analysis of data, and different assumptions that can distort the results.
Previous overview studies that summarized multiple investigations found that IQ differences in humans were influenced by brain size between six and eleven percent. However, the metastudy published by Pietschnig and his team, which included significantly more participants, found that a larger brain can only explain differences in intelligence by six to eight percent. The researchers conclude that while this effect is remarkably robust, it only has a small to moderate impact.
In conclusion, the correlation between intelligence and brain size is often overestimated, and a larger brain can only explain a small portion of IQ differences. While the debate on this topic continues, the researchers suggest that a combination of brain measurement and validated intelligence tests is necessary to investigate the relationship between intelligence and brain size in detail.
