Intelligence in the brain

Intelligence is one of the abstract concepts that throughout human existence has been debated by various generations of scientists, philosophers and psychologists. Above all, people have debated whether intelligence is a single ability that can be quantified or several individual intelligences, such as emotional, spatial, linguistic and logical-mathematical intelligence, among many others defended by various experts on the subject. Whether intelligence is one or many, and however many definitions it has been given, most agree on taking it as the capacity to adapt to the environment, to reason, plan and learn, in order to make sense of it and solve the problems it poses.

Where does intelligence reside?

The origin of intelligence is something even more complex, and for which no concrete answer has yet been found. A large number of neurological studies have tried to find what areas and what factors of the brain are those that determine intelligence in a person, but the results obtained have been varied. Studies have found that intelligence is correlated with the volume of gray matter in the different areas of the brain, which is due to the integrity of the white matter, which varies depending on sex, being related to the parietal and frontal regions in men and with the frontal lobe in women, which varies with age because the proportions of the brain are not the same in all stages of life, which is due to the efficiency of the distributed cortical areas, among many other relationships with the various parts of the brain; however, although each result is tied to the sample of the study that produced it, they do not yield concrete, generalizable conclusions, since the correlation coefficients are low, between 0.15 and 0.35.

The only thing concluded from the large number of results is that intelligence cannot be attributed to a single brain region, but on the contrary, it encompasses a whole network of brain regions distributed across higher-order cortices, also called the frontoparietal network, which covers most of the previously mentioned areas.

And likewise, human intelligence cannot be explained solely by its brain structure and by the activation areas that can be observed on an MRI scan. Because although the human being has an intelligence that stands out compared to other animals, its brain structure is not so different from that of other mammals; the size and number of neurons in the human brain are not an evolutionary advantage that could explain our intelligence, since there are species with larger brains and with more neurons than humans.

So, if intelligence is not due to the large-scale anatomy of the brain, we should analyze its most fundamental units and the connections between them, that is, the synapse: the relationship between neurons for the transfer of information.

It is not the quantity but the efficiency

When it comes to intelligence, less is more. It is not about the number of neurons, but how they work. There is evidence that, unlike what is usually imagined, it is not whoever uses the brain more, but who uses it less, referring to the energy required to carry out a cognitive process and the time it takes.

There is evidence, mainly for tasks of low to moderate difficulty, that intelligence is related to the efficiency with which the brain works, that is, it can be explained in simple terms such as the relationship between energy consumed and work produced. Therefore, smarter people tend to use less energy for their synaptic process, making them able to use their energy more efficiently.

And this efficiency is also related to the presence of thinner and scarcer neuronal connections, that is, those with fewer dendrites and lower density in the cerebral cortex are more intelligent, causing less neuronal activity.

However, people, regardless of their IQ, use their brain equally: it is a myth that some people use a higher percentage of their brain than others, since everyone uses 100% of their brain functions throughout the day.

Intelligence still holds several unknowns that science has not yet fully resolved, but if one can be sure of something, it is that intelligence is largely based on knowledge; that is why we invite you to continue enriching your knowledge with more scientific cookies, here at Science Cookies.