Larger Pupils are Correlated with Higher Fluid Intelligence and Attention Control

Article: Pupil Size Is a Marker of Intelligence
Source: Scientific American, via JCAHPO and AOA
Published: June 2, 2021

New research finds a possible link between baseline pupil size and individual difference in cognitive ability. Beyond reacting to light intensity, pupils also indicate arousal, interest, and mental effort. Curious about the connection between pupil dilations as an indicator of mental effort, the researchers wanted to investigate whether pupil size was also a measure of intelligence. The study involved 500 participants aged 18 to 35, whose pupils were measured with an eye tracker while they stared at a blank computer screen for up to four minutes. These participants then performed tests in fluid intelligence (the capacity to reason through new problems), working memory capacity (the ability to remember information over a period of time), and attention control (the ability to focus attention amid distractions and interference). After controlling for age-related decreases in pupil size, the researchers found that larger baseline pupil size was correlated with better performance in fluid intelligence and attention control and, to a lesser degree, working memory capacity in all but the brightest lighting conditions. They hypothesize that people with larger pupils at rest have greater regulation of activity by the locus coeruleus, a nucleus situated in the upper brain stem that is responsible for releasing norepinephrine as well as regulating a range of neural processes such as perception, attention, learning and memory. Though more research is needed to determine why larger pupils are correlated with higher fluid intelligence and attention control, studies such as this provide a better glimpse through that proverbial "window of the soul."

My rating of this study: ⭐⭐

Tsukahara JS and Engle RW. "Is baseline pupil size related to cognitive ability? Yes (under proper lighting conditions)." Cognition.  211:104643. June 2021. https://doi.org/10.1016/j.cognition.2021.104643