Children's pupils may reveal shifting attention in ADHD, especially when off medication

by Sanjukta Mondal, Medical Xpress

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The eyes are more than lenses to the outside world; they can also be windows that offer a glimpse into what's happening inside our bodies. What if the eyes could help us understand how attention shifts from one moment to the next? Scientists are now testing whether tiny changes in pupil size can serve as a physiological marker of these fluctuations in children with attention-deficit/hyperactivity disorder (ADHD).

Pupil diameter automatically shrinks and expands in response to brain systems that regulate alertness, arousal and attention. In a recent study published in Scientific Reports, researchers explored whether changes in pupil size during a memory task could tell them something useful about how well children performed and whether this changed depending on their ADHD medication. They tracked the eye movements of children with and without ADHD as they completed a visual memory task.

When children with ADHD were off medication, their pupil size fluctuated more from one trial to the next than in children without ADHD, even after accounting for differences in task difficulty, age and IQ. On medication, their pupils responded more strongly at key moments in the task, while trial-to-trial variability dropped compared with when they were off medication. Also, children with ADHD who were not taking medication responded more quickly to the memory tasks, but this speed came at the cost of lower accuracy.

Tracking the eyes of a wandering mind

Nobody's attention stays perfectly steady. It naturally drifts up and down, even during simple mental tasks. However, for people with ADHD, a common condition affecting 5–7% of people worldwide, these swings are much greater. Contrary to the popular notion, ADHD isn't just about being distracted; it's about attention that is genuinely less stable from moment to moment.

Conventional clinical and computer-based tests typically reduce a child's performance to an overall average, making it difficult to capture the rapid, second-by-second fluctuations that can occur in ADHD. Eye movements, including pupil dilation, respond quickly to changes in mental focus, making them promising physiological markers.

Previous eye-tracking research largely focused on average pupil size across an entire task rather than on how it changed from one question to the next. Researchers set out to harness these often-missed fluctuations, hoping to answer two key questions: Do they have a connection to memory performance, and does medication change that pattern?

To obtain the missing data, the researchers examined existing public eye-tracking data from 50 Chilean children ages 10–12—28 with ADHD and 22 without. Each child sat in front of a screen and played a 30-minute memory game while a high-tech eye tracker (the EyeLink 1000) monitored their pupils, capturing tiny changes 1,000 times per second. They compared three groups: children without ADHD (controls), children with ADHD off their medication for 24 hours, and children with ADHD tested 2–2.5 hours after taking their medication.

What the pupils revealed

They found that children with ADHD who were off medication showed pupil sizes that varied about 23% more from question to question than children without ADHD. The difference held up for the group as a whole but did not meet the threshold for statistical significance after individual results were corrected for statistical error.

Also, within a single test trial, pupil variability was lower in unmedicated children with ADHD (0.699) than in the control group (0.772). This contradicted the researchers' initial prediction that within-trial fluctuations among unmedicated children would be higher.

For the 17 children who were tested both on and off medication, taking methylphenidate made a clear difference. Their pupil size varied less from question to question, and their pupils expanded more during the task's decision-making moments. As a result, their overall pupil response pattern looked more like that of children without ADHD.

The results are compelling, but the researchers urge caution. Pupil variability doesn't come from a single source. It reflects a mix of different brain processes, not attention alone. So, rather than using pupil size as a standalone test for ADHD, it is better used alongside other cognitive and physiological tests for the condition.

Written for you by our author Sanjukta Mondal, edited by Gaby Clark, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.

Publication details

Saumya Yadav et al, Trial-level pupil dynamics reflect attention-related variability and medication-associated modulation in ADHD, Scientific Reports (2026). DOI: 10.1038/s41598-026-68871-2

Journal information: Scientific Reports

Key medical concepts

Attention Deficit Hyperactivity DisorderMethylphenidate

Clinical categories

PsychiatryChildren's healthNeurology Who's behind this story?

Sanjukta Mondal

Master's in Chemistry. Freelance science journalist and communicator. Published in Chemistry World, BioSpace, and The Hindu. Full profile →

Gaby Clark

MA in English, copy editor since 2021 with experience in higher education and health content. Dedicated to trustworthy science news. Full profile →

Robert Egan

Bachelor's in mathematical biology, Master's in creative writing. Well-traveled with unique perspectives on science and language. Full profile →

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