Scientists link pupil dilation to the brain’s all-important 'working memory' levels

Two things often happen at the same time in a busy kitchen: plates clatter into the dishwasher and a mental note pops up that the soap dispenser is running low. The brain keeps both thoughts alive for a few seconds, steers the hands, and updates the grocery list.

Scientists call this swift juggle “working memory,” yet most people know it simply as keeping track of what matters right now.

Researchers have spent decades mapping this mental scratchpad, but its quirks still surprise. The latest clue comes from the eyes.

A fresh study suggests that the way a person’s pupils change while they concentrate hints at how well that mental scratchpad is working.

Why working memory matters

Working memory does more than hold stray reminders; it stitches together phone digits until they are dialed, keeps track of a spoken sentence until the meaning lands, and buffers half-finished ideas during problem-solving.

Unlike long-term memory, it works on a tight clock measured in seconds. Because the capacity is finite – typically three to seven items at once – small differences in efficiency can ripple through reading, mathematics, and decision-making.

Psychologists often compare working-memory scores among people of similar age, finding wide gaps. Some differences trace back to genetics, sleep quality, and stress.

Others appear linked to how sharply someone focuses in the moment. Pinning down those fleeting attentional shifts has been tough, so a team at the University of Texas at Arlington turned to a simple, involuntary signal from the eye.

Eyes signal focus level

Assistant professor of psychology Matthew Robison and doctoral student Lauren D. Garner, both from UTA’s CAM Lab, recruited 179 undergraduate volunteers for a set of memory challenges designed to last only a few heartbeats.

An eye-tracking camera, like the one an optometrist uses, recorded pupil size while each participant tried to remember colors, shapes, or letters flashed on a screen. The pupils were expected to widen in the dimly lit lab, yet they also fluctuated with mental effort.

“What we found was that the lowest performers on the tasks showed less pupil dilation,” Robison explained.

“For the highest-performing participants, pupil dilations were larger overall, and they were more discerning about the information they were asked to recall.”

Working memory and larger pupils

Pupil dilation is controlled by the autonomic nervous system, the same circuitry that speeds the heartbeat under stress.

Earlier research showed the pupils twitch in sync with challenges such as mental arithmetic, signaling rising cognitive load.

This new work links that physical reaction directly to the accuracy of working memory: bigger, more precisely timed dilations tracked with sharper recall across the entire group.

The study appears in Attention, Perception & Psychophysics, and its key takeaway has immediate practical value.

Teachers, coaches, and clinicians could someday use a non-invasive gaze sensor to see whether a student’s attention slips long before test scores reveal a problem.

Attention and cognitive load

The eye-memory link lines up with a well-known theory called “resource allocation,” which proposes that the brain funnels more energy – oxygen, glucose, and electrical activity – toward information flagged as important.

The dilating pupil mirrors that surge. When the surge is weak or mistimed, fewer details make it onto the mental scratchpad.

Everyday distractions, from buzzing phones to background chatter, can sap that resource.

On the flip side, practice with activities that demand steady focus, such as playing certain musical instruments or fast-paced video games, has been shown to nudge working-memory scores upward.

Those lifestyle influences mesh neatly with the new pupil data, suggesting the eyes could become a quick biofeedback tool for attention training.

Classroom and clinic uses

Individualized instruction often starts with trial and error. A live readout of pupil patterns could speed the process by showing when a student is overwhelmed or under-engaged in real time.

That information might guide a teacher to slow the pace, rephrase directions, or add a break exactly when it counts.

“We found that people who more intensely and consistently paid attention, as measured by their pupils being dilated more, performed better on the memory tasks,” Robison enthused.

“Importantly, we found high performers also showed more pupil sensitivity compared to low-performing participants. This is exciting research because it adds another valuable piece of the puzzle to our understanding of why working memory varies between individuals.”

Keeping working memory in shape

While future gadgets may monitor focus automatically, old-school habits still help. Brief pauses during dense reading let fresh material settle before more arrives.

Organizing tidbits into tiny clusters – phone numbers into three short chunks, for example – reduces the load.

Mindfulness exercises that train sustained attention have gained traction, and emerging evidence suggests they may slightly enlarge working-memory capacity over weeks of practice.

Even aerobic movement matters. Studies tracking middle-aged adults find that brisk walking improves blood flow to brain regions involved in executive control, indirectly supporting the memory buffer.

The take-home message echoes common sense: whatever boosts overall brain health tends to support the few precious slots on that internal notepad.

Pupils, working memory, and future study

The UT Arlington experiment adds a clear, measurable signpost to the study of working memory. By tying pupil behavior to test performance in 179 young adults, it builds a bridge between subjective focus and objective outcomes.

Larger studies spanning different ages and cultures are already in the planning stages, aiming to see whether the same patterns hold in childhood development, aging, and cognitive disorders.

If they do, tracking a tiny change in the eyes might soon guide personalized learning plans, aid early diagnoses of attention deficits, or help engineers design user interfaces that adapt to a person’s real-time mental load.

For now, the findings serve as a reminder that the eyes are broadcasting more than mood or alertness – they may be giving away the secrets of how we juggle the small but vital tasks that keep life running smoothly.

The full study was published in the journal Attention Perception & Psychophysics

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–