Eye pupil changes may reflect attention shifts in children with ADHD, study suggests

Research indicates that fluctuations in pupil size during visual tasks could provide new insights into attention regulation in children with ADHD, with medication potentially stabilising eye responses.

Researchers are increasingly looking beyond behaviour alone for clues to attention disorders, and the eye may offer one such clue. A study published in Scientific Reports found that small changes in pupil size during a visual memory task differed between children with attention-deficit/hyperactivity disorder and children without the condition, suggesting that the pupil may reflect fluctuations in mental effort rather than simply where a child is looking. The work was reported by ScienceAlert and discussed by Entekhab.

The study examined 50 children in Chile aged 10 to 12, including 28 with combined-type ADHD and 22 who did not have ADHD or another neurodevelopmental disorder. While the children played a memory game that required them to remember the position of dots after a distracting image appeared, eye-tracking equipment recorded pupil changes 1,000 times a second. The researchers found that children with ADHD who were not taking medication showed greater variation in pupil size from trial to trial than the control group, which they said may point to more unstable levels of attention or engagement during the task.

The results became more striking when the researchers looked at 17 children with ADHD who completed the task both after a 24-hour break from methylphenidate and again while taking their usual medication. On medication, the children’s pupil responses were stronger during the task and less variable across trials, making their pattern look more like that of the control group. The Scientific Reports paper said the pupil changes also tracked performance and reaction-time variability, though the authors stopped short of claiming that the drug had simply normalised attention.

That caution matters. The researchers noted that methylphenidate can affect the body’s systems that influence pupil size, which means the changes could reflect a direct drug effect, an improvement in attention, or both. The study was also small and carried out in a tightly controlled laboratory setting, not in a classroom or other real-world environment. For now, the findings do not offer a diagnostic test for ADHD. But they do add to growing evidence that eye-tracking may help scientists measure how attention shifts over time and how children respond to treatment.