Anatomy of intelligence - what a glance into our brain reveals about our cognitive skills

According to a new study, fluid intelligence - a major component of our intelligence - is dependent on the energy available to us and our brain size. 

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"Intelligence is what is measured by intelligence tests". This quotation sums up the biggest problem of the research about intelligence: and that's because intelligence is no absolute measurement but rather a human-made theoretical construct. As hard as it is to theoretically define the term of intelligence, in practice and in everyday life, it becomes quite clear what intelligence really is. And already in school is this evident: There are children who have no trouble learning and remembering new things, while others strugglee to keep up with their classmates. Differences like these continue throughout life.  

Does intelligence determine success at school?

What does intelligence depend on?Even in terms of a child's success at school, it is relatively complex to measure the influence of intelligence. Is it really a child's intelligence that determines their success or do other factors such as personality traits also have a say in it? To give an example, researchers were able to demonstrate the importance of self control for a child's success at school. But even though this shows that other factors are also important in determining success, it is still evident that intelligence is one of the very vital and influencing factors. 

Dichotomy of intelligence 

In order to study and measure intelligence more easily, scientists have divided the human intelligence into two components: 

Crystallized intelligence: Expresses the factual knowledge a person acquires throughout their life. 

Fluid intelligence: Describes the ability for deductive reasoning, the learning of new things and behaving appropriately and according to a situation. 

A new study examined the neurological influence factors on fluid intelligence. Are there elements in the brain that influence how distinctive and strong fluid intelligence is? Can we already get a sense of how well a person will solve certain tasks just by looking into their brain? 

NAA and brain size

Mapping of the brainThe researchers at the Beckman Institutes for Advanced Science and Technology were particularly interested in the effect of the substance NAA - a by-product of glucose - as well as the brain size. NAA is an indicator for how much energy our brain has left to use hence its importance for the researchers. The concentration of NAA was measured with the help of magnetic resonance spectroscopy, whereas the brain size was calculated with magnetic resonance tomography. 

Fluid intelligence tests

In the experiment, a person's fluid intelligence was detected based on two categories: Firstly, the deductive reasoning ability (e.g. continuing a series of numbers), and secondly, the ability of verbal and spatial conclusion (e.g. analogies). A total of 211 participants were examined. 

The results 

Patience determines successThe results paint quite a differentiated picture: It seems that the concentration of NAA and the brain size are resonsible for different abilities. The researchers found that there was a positive correlation between the brain size and the numerical deductive reasoning ability. Therefore, a person with a bigger brain size was able to achieve better results in the numerical deductive reasoning category. On the other hand, there was another correlation between the amount of NAA in the brain and the verbal deductive reasoning. The higher the amount of NAA in the brain, the better were a person's results in the verbal deductive reasoning category. 

Conclusion: Biological foundation of intelligence 

Our intelligence - however you want to define it - does of course, depend on a number of factors. But this study showed that biological and neuroanatomical aspects such as brain size and the amount of energy available to the brain do also play a significant role. 

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Sources:

Paul, E. J., Larsen, R. J., Nikolaidis, A., Ward, N., Hillman, C. H., Cohen, N. J., Kramer, A. F., & Barbey, A. K. (2016). Dissociable brain biomarkers of fluid intelligence. NeuroImage, 137, 201-211.

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