Researchers suggest that subtle variations in pupil size could provide a novel method to monitor attention fluctuations in children with ADHD, with medication influencing pupil responses and attention stability.
Researchers say tiny changes in the pupil may offer a fresh way to track how attention rises and falls in children with ADHD, especially when medication is involved. A study in Scientific Reports looked at eye-tracking data from 50 children in Chile aged 10 to 12 and found that those with ADHD showed more trial-to-trial variation in pupil size than children without the condition. The findings add to a growing body of work suggesting that pupil behaviour could reflect moment-to-moment shifts in mental focus rather than only broad differences in performance.
The team examined children carrying out a visuospatial working-memory task while a high-speed eye tracker recorded pupil changes 1,000 times a second. Among children with ADHD who were tested after a washout period, pupil size varied more from one trial to the next, even after accounting for age, IQ and task difficulty. The study also found that, within a single trial, unmedicated children with ADHD showed lower pupil variability than controls, a result that ran counter to the researchers’ original expectation.
Medication appeared to alter the pattern. In the subgroup of 17 children tested both on and off methylphenidate, pupil responses became steadier and more closely resembled those of the control group when the children were on treatment. Their pupils also dilated more at key decision-making points in the task. The same children responded faster when off medication, but that speed came with reduced accuracy, underscoring the trade-off between quick responses and careful performance.
The latest work builds on earlier studies that linked pupil size to attention and working-memory performance in ADHD. Research published in 2017 also found that pupil size tracked reaction-time variability during a similar task, while other studies have shown that methylphenidate can change pupil diameter in children with ADHD. Taken together, the evidence suggests that pupil dynamics may one day help researchers measure attention-related instability more precisely. For now, the authors caution that pupil size is influenced by more than attention alone, so it is unlikely to become a stand-alone diagnostic test.
Disclaimer: This content is for informational purposes only and is not intended to be a substitute for professional medical judgment, advice, diagnosis, or treatment.
