Is IQ reflected in the brain?
Is IQ reflected in the brain?
There are people with exceptionally high IQs, while others have low IQs. But can the difference also be seen in the brain, asks an eighth-grader?
The editor's answer is:
Answer from Dr. Erhan Genç, head of the MRI group in the Department of Psychology and Neurosciences at the TU Dortmund: That's exactly what people were asking themselves 100 years ago, which is why they weighed brains and measured their size. In fact, there is a fairly robust connection between brain mass and intelligence: more intelligent people have more brain mass, which is also shown by recent studies. Today, however, the mass of the brain is recorded using magnetic resonance imaging (also known as magnetic resonance imaging, MRI).
In addition, in recent years attempts have been made to localize places in the brain that are particularly important for intelligence. A network of areas was discovered that is particularly active when solving intelligence tasks. These areas primarily include the frontal and parietal lobes. If they are very pronounced in the brain mass, this speaks for high intelligence.
The next step in the research was to take a closer look at the networks between these important areas. Diffusion-weighted magnetic resonance imaging can be used to track how water flows in the brain. Because water molecules move along the nerve fibers, you can see how they are laid out. The result of these observations: In intelligent people, the flow of water is more directed, more directed. This means that the connections between the brain areas important for intelligence are very efficient in them.
If you no longer focus on the connections between brain areas when observing the flow of water, but on local networks, for example in the cerebral cortex, you discover another factor for intelligence: the density of dendrites. Dendrites are cell extensions in the brain with which a nerve cell makes contact with other nerve cells. They are found in the neuropil, a dense network of nerves. The result: The density of dendrites is lower in more intelligent people, so their brains are less networked and therefore more efficient - that was the result of a study that I published in 2018 with Christoph Fraenz and other colleagues.
We explain it like this: In order to solve a task, you have to separate the relevant from the irrelevant. Theoretically, there are two ways to do this: improve the signal or suppress the noise, i.e. irrelevant signals. We found the lower density of dendrites in intelligent people primarily in the parietal and frontal brain areas, where a lot of information arrives. Therefore, we assume that the lower dendrite density suppresses unimportant information. This enables intelligent people to solve tasks more efficiently.
Incidentally, the current research situation suggests that there are also certain areas of the brain in which, in contrast, a higher density of dendrites is a characteristic of intelligence - this is probably dependent on the respective task of the area.
In addition to these examinations of the brain structure, one can also observe the activity of the brain when solving tasks with the magnetic resonance tomograph or electroencephalography (EEG). This shows that smart people don't have to exert as much effort when it comes to very easy and moderately difficult tasks, and they only reach their full potential when it comes to difficult tasks. Average intelligent people, on the other hand, are most active on moderately difficult tasks. However, this only applies to tasks from the area of so-called fluid intelligence, which involves logical and abstract thinking. Tasks from the area of crystalline intelligence, on the other hand, relate to learned and cultural knowledge. The brain activity is always similar, regardless of the difficulty of the task and the subject.
In the future, my colleagues and I want to systematically examine brain activity when solving intelligence tasks in order to better understand which brain characteristics are really best for predicting intelligence.