People with large pupils tend to be smarter

This eye trait would correspond, according to research, to a higher IQ level.

It is often said that the eyes are the mirror of the soul, and there is some truth to that. It has long been known that pupils not only dilate and contract in reaction to light, but also in reaction to mental processes occurring in our brains.

For example, when we see something or someone we are attracted to, they dilate more in order not to lose detail of what is in front of us. Similarly, in simple memorization tasks, it has been seen that the pupil expands as elements are retained in memory and contracts each time something previously memorized is recalled.

Thus, our gaze expresses more of our inner world than we might expect. However, recent research takes this idea further, providing new evidence about the relationship between pupil behavior and our psychological makeup: people with larger pupils tend to be more intelligent, statistically speaking..

The link between pupils and fluid intelligence

The results of this research, published in the journal Cognitive Psychology by a team of U.S. psychologists, show that pupil diameter is correlated with higher intelligence scores.. That is, groups of people who have larger pupils have a greater chance of being more intelligent than the rest, although this rule does not necessarily hold true for all individuals.

To conduct this research, a group of 331 volunteers was used and pupil size was measured at which pupils adopted their "default" size to ensure that brightness levels did not affect the results. In addition, the psychologists took into account variables such as age, sex or the consumption of certain substances such as nicotine. Once the influence of these variables was subtracted from the equation, the correlation between pupil size and intelligence appeared.

However, the measure of intelligence whose relationship to pupil diameter was recorded by this group of psychologists was not just any intelligence.

Specifically, it was fluid intelligence, one of the most important components of IQ. Basically, fluid intelligence refers to the mental agility with which we find solutions to unforeseen and novel problems.. Therefore, it is a type of intelligence that does not depend on our cultural level or on the knowledge we have acquired over the years.

How can this be explained?

What causes this relationship between pupil size and higher scores in fluid intelligence is, for the moment, a mystery. Of course, it could be a spurious correlation, it could be a spurious correlationIt could be the result of a curious coincidence, or it could reflect that there is a variable between the two that causes them both at the same time. For example, it could be that people with larger than normal pupils come from a line of ancestors with neuroanatomical characteristics that make them more intelligent.

Another rough explanation is proposed by Jason S. Tsukahara, one of the researchers responsible for the study. The answer could lie in a network of neurons sensitive to a substance called noradrenaline that are located in a part of the brain known as the locus coeruleus, located in the brainstem. He points out that other research has shown a relationship between the level of activity of this group of nerve cells and pupil size. At the same time, noradrenaline makes neurons more likely to communicate with each other, thereby creating new neural pathways that make it easier to find possible solutions and consider more options.

To clarify this, it will be necessary to repeat research of this type in various contexts and see if the correlation is present in each of them. In that way, from there, it will be possible to begin to develop a theory to explain the phenomenon..