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What Your Eyes Can Reveal About Your Intelligence

According to folk wisdom, the eyes are the window to the soul. Indeed, a glimpse at one’s eyes and gaze can reveal a great deal about a person’s emotional state: one’s hopes, interests, worries, or a sleepless night. But there’s one more surprising quality you can tell by looking at someone’s eyes - intelligence. Recent research drew a surprising link between pupil size and intelligence, claiming they can predict a person’s approximate IQ by simply measuring their pupils.

The intelligence and pupil size connection

The research was conducted at the Georgia Institute of Technology. Initially, the researchers intended to measure pupil dilations as a sign of mental effort in 500 people aged 18-35, but they soon noticed that the participants with a larger pupil diameter also performed better on memory tasks. This made them suspect that there’s more behind the story, so they started measuring the participants’ pupil diameter and had them do reasoning, memory, and attention tasks to see if there’s any correlation between pupil size and cognitive performance.
Pupil Size and Intelligence eye closeup
Interestingly, pupil diameters vary a lot from person to person, ranging from 2-8 millimeters. But how do you measure someone’s pupil, to begin with? To make sure that the pupils are in a relaxed state, participants are asked to stare at a blank screen for a couple of minutes. They wear eye trackers that are used in calculating the diameter of the pupil. The test results showed a clear connection between one’s intelligence and pupil size.
The authors of the study proceeded to observe the same relationship in two other experiments they conducted, and they state that the effect is so clear and easy to notice you could do it with the naked eye. “You should be able to tell who scored the highest or the lowest on the cognitive tests just by looking at them,” the researchers state.
The authors conclude that having a larger pupil means you also have higher fluid intelligence, which is the ability to reason and think in a flexible way, often when confronted with new tasks. Larger pupil diameter was also correlated with better focus and working memory.

How are pupil size and intelligence connected?

Pupil Size and Intelligence eye exam
Since this is the first study to establish the connection between pupil size and intelligence, it’s difficult to say how the two are connected. The study authors have a theory that the connection may lie in the brain. Previous studies have noticed that a larger pupil is associated with an improved function in an area of the brain that helps consolidate information.
This brain area is called the locus coeruleus, and its job is to make the hormone noradrenaline (norepinephrine in the brain). It is the same hormone that makes us jump into action and think more efficiently in stressful situations. Scientists know that the locus coeruleus influences our memory, attention, and learning, all of which are important measures of fluid intelligence. Moreover, it helps different parts of the brain work together, and the impaired functioning in the locus coeruleus is related to depression, Alzheimer's disease, Parkinson's, and attention deficit hyperactivity disorder (ADHD).
The researchers suggest that people with a larger pupil diameter may have a larger or better functioning locus coeruleus, and they will hopefully confirm that in future studies.
One last interesting observation of the study is that the pupil size and intelligence correlation holds even in older participants. This is important because pupil size tends to decrease with age, and older participants did have more constricted pupils than younger ones. Still, once the researchers looked at the pupil size correlation in the older age group, they still saw a correlation between cognitive prowess and pupil size.
Hopefully, the authors will explore the fascinating correlation between pupil size and cognitive abilities in future studies - we’ll definitely keep you posted.
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