New Insights on How Pupils May Reflect Attention Patterns in ADHD

It’s often said that our eyes are windows to the soul, but researchers are starting to think they might reveal another aspect: the rhythm of our attention.

Interestingly, the key might not be in what we look at, but rather in the minute changes in our pupils as our brains navigate memories, distractions, and decisions.

A recent study indicates that this attention rhythm could be subtly altered in children diagnosed with attention deficit hyperactivity disorder (ADHD).

ADHD, as many know, is a neurodevelopmental condition marked by ongoing issues with attention, impulsivity, and hyperactivity. It’s worth noting that attention isn’t some simple on-off switch; it can be steady one moment and then drift off the next.

As it stands, there’s no one definitive test for ADHD. Instead, the diagnosis involves a combination of medical evaluations, personal history, and behavioral observations across various settings.

Researchers at the Indraprastha Institute of Information Technology Delhi were curious if pupil responses could offer additional insights into this condition.

They reexamined existing eye-tracking data from 50 kids aged 10 to 12 in Chile, where 28 had been diagnosed with the combined type of ADHD, while the remaining 22 had no neurodevelopmental diagnoses.

During the study, the children engaged in a memory game where they watched dots appear on a grid and had to memorize their locations. After a distracting image flashed on the screen, they had to determine if a new dot was in a previously seen position.

Each child repeated this task 160 times, with their pupil sizes measured a thousand times per second using eye-tracking technology.

Pupil size does more than just respond to light—it also reacts to levels of effort, arousal, fatigue, and engagement.

While past studies often looked at average pupil size, this research sought to determine whether individual children’s pupils behaved consistently when faced with the same challenges.

As first author Saumya Yadav expressed, “Examining how pupil responses fluctuate across trials may uncover details that average measurements miss.”

The researchers found that after adjusting for age, IQ, and task difficulty, there was about a 23% greater variability in the pupil responses of unmedicated children with ADHD compared to their peers.

However, trends shifted based on how variability was gauged. While pupil reactions differed more across trials, they were less variable within individual trials for unmedicated children with ADHD. This hints that various measurements might reflect distinct aspects of pupil behavior.

Among the unmedicated ADHD group, those who exhibited greater pupil variability also tended to have less accuracy in their answers, suggesting that their pupils may reflect changes in attention or engagement.

But it’s important to remember that a wandering pupil doesn’t equate to a wandering mind. Various factors influence pupil size, making it an indirect reflection of attention.

Another interesting facet of the study was that 17 children with ADHD underwent the task twice: once after stopping methylphenidate for 24 hours and again after taking their regular medication.

When on medication, these children displayed stronger pupil responses during the task, with less fluctuation between trials. Their responses started to resemble those of the control group.

It might be tempting to suggest that medication “normalized” their attention, but the researchers caution against making that leap.

Methylphenidate could directly alter physiological reactions that affect pupil size. The research couldn’t definitively establish whether any differences were due to enhanced attention, the drug’s physiological effects, or a mixture of both.

Yadav pointed out, “We wouldn’t view this as evidence that medication ‘normalized’ attention.”

They were also unsure about exact dosages or formulations taken by the children, and the two tests were spaced by approximately six months, which might have introduced other developmental factors.

There’s another layer of caution here: although the variability metrics were strong, comparisons between individuals fell just shy of statistical significance after adjustments were made.

While greater pupil variability linked to lower accuracy was noted in the unmedicated ADHD group, this connection wasn’t significantly stronger than the same pattern observed in controls.

Yadav cautioned, “It’s still premature to think of pupil measurements as a clinical diagnostic tool.”

The study was relatively small and used existing data, tackling a controlled laboratory task, while real-life classroom dynamics are far messier.

To truly ascertain whether these pupil patterns hold across diverse individuals and everyday contexts, larger and more extensive studies will be necessary.

Should these findings prove reliable, pupil tracking wouldn’t replace traditional methods like doctor evaluations and interviews. Instead, it could provide valuable insights into how a person’s attention shifts over time or responds to treatment.

At present, though, pupils can’t diagnose ADHD. Yet, they might unveil something often obscured: the fluid nature of attention as it shifts, fades, and resurfaces moment to moment.

This research has appeared in Scientific Reports.