A study in 2004 found that IQ is related to the amount of gray matter in the brain, which is distributed in every corner of the brain. More importantly, the study found that the existence of a large amount of gray matter in some parts has a great relationship with IQ. Researchers at the University of California scanned the brains of 47 adults with magnetic resonance imaging (MRI) and gave them a standard IQ test. The researchers divided the brain into several regions and then scanned the gray matter in each region. There is gray matter in all parts of the brain, forming a network to process information. The results of scanning and testing show that people with higher IQ scores have higher gray matter levels in 24 brain regions. These 24 regions are located in various parts of the brain, most of which are related to memory, attention and language. Researchers speculate that people's intelligence in different aspects may depend on the content of gray matter in different areas of the brain, which makes nerve cells process information more effectively.
Richard Hale of the University of California, Irvine, who led the study, said: "This is why a person who is good at math is not good at spelling, while another person with the same IQ is just the opposite." Another survey led by Haier shows that men think more about gray matter, while women rely more on white matter (another type of basic brain tissue). This study found that only 6% of the gray matter in the human brain is related to IQ. However, it provides the first evidence that brain matter content is related to intelligence.