Imagine being able to study attention not only by asking someone to complete a test, but also by observing something as subtle as the movement of their pupils. That is the idea behind emerging ADHD research using eye-tracking and pupillometry.
A new Indian study from IIIT-Delhi, published in Scientific Reports in September 2026, explored whether trial-by-trial pupil changes could provide physiological clues about attention and task performance in children with ADHD. The study included 50 children—28 with ADHD and 22 controls—with an average age of 10.6 years.
Importantly, pupil measurements are being investigated as a research tool, not as a standalone ADHD diagnostic test.
What Is ADHD?
ADHD, or attention-deficit/hyperactivity disorder, is a neurodevelopmental condition associated with difficulties involving attention, impulsivity and hyperactivity.
Attention can fluctuate throughout a task, making it difficult to capture with a single behavioural measurement. Researchers are therefore exploring physiological signals that may complement traditional assessments.
Why Study the Pupils?
The pupils respond to changes in arousal and cognitive activity, making them a potential indirect window into brain processes related to attention.
Earlier research has shown that pupil size can track attentional performance during working-memory tasks, while newer studies are examining more detailed pupil dynamics rather than simply measuring pupil size.
What Did the New Indian Study Examine?
The 2026 study from IIIT-Delhi’s Human-Machine Interaction Lab used eye-tracking while children completed a visuospatial working-memory task.
Researchers examined:
- Differences in pupil variability between trials
- Changes within individual trials
- Task-related pupil responses
- Links between pupil patterns and task accuracy
- Differences between ADHD participants on and off stimulant medication
The researchers found approximately 23% greater residual inter-trial pupil variance in the off-medication ADHD group compared with controls, although this difference did not remain statistically significant after false-discovery-rate correction.
What Does Pupil Variability Tell Us?
Pupil variability may provide additional information about fluctuations in attention and task performance, but it is not specific enough to diagnose ADHD on its own.
In the study, greater inter-trial variability was associated with lower task accuracy in the off-medication ADHD condition. The researchers described pupil dynamics as complementary physiological information rather than a definitive measure of attention.
Does ADHD Change Pupil Responses?
Research suggests that pupil responses can differ between people with ADHD and controls during certain cognitive tasks.
A 2025 study involving **76 adults—34 with ADHD and 42 controls—**found reduced low-frequency pupil oscillations in participants with ADHD. The researchers suggested that pupillary measurements could potentially contribute to future ADHD evaluation and classification research.
However, these findings should not be interpreted as meaning that a particular pupil pattern proves someone has ADHD.
Could Medication Affect Pupil Measurements?
Yes. Medication status may influence pupil responses, which is one reason researchers must carefully control experimental conditions.
In the 2026 Indian study, the on-medication ADHD condition showed an increased relative pupil response during the probe window and reduced inter-trial variance. However, the authors noted that medication effects could not be separated completely from other session-related factors. (Nature)
Pupils and the Brain’s Attention System
Pupil responses are connected with brain systems involved in arousal and attention, including pathways involving norepinephrine and the locus coeruleus.
This helps explain why researchers are interested in pupillometry: it may offer a relatively simple physiological signal that can be studied alongside behavioural performance.
Still, pupil changes can be influenced by many factors, including lighting, emotional state, medication and cognitive workload.
Can an Eye Test Diagnose ADHD?
Not currently. Pupil or eye-tracking measurements should not be used alone to diagnose ADHD.
ADHD assessment involves clinical evaluation and consideration of symptoms, developmental history and functioning across relevant settings. Pupillometry remains an area of research that could potentially complement existing assessment methods in the future.
Why This Research Matters in India
Research from IIIT-Delhi, New Delhi, adds an important Indian contribution to the growing international literature on ADHD, attention and eye-tracking.
The study is particularly interesting because it moves beyond simply asking whether pupils are larger or smaller. It examines how pupil responses vary from trial to trial, potentially providing more detailed information about fluctuations in cognitive performance. (Nature)
What Could Happen Next?
Future studies may investigate larger and more diverse populations, different age groups, longer follow-up periods and how pupil measurements perform alongside established clinical assessments.
The goal would not necessarily be to replace clinical diagnosis, but potentially to develop objective, complementary measures that help researchers better understand attention and treatment-related changes.
Key Takeaway
Your pupils cannot currently diagnose ADHD, but they may provide researchers with valuable clues about attention and brain activity.
The new Indian study suggests that trial-level pupil dynamics can provide complementary information about attention-related variability and task performance in children with ADHD. More research is needed before such measurements can become part of routine clinical assessment.
ADHD and the Brain: Frequently Asked Questions
Can pupil size indicate ADHD?
Pupil responses may differ in ADHD research, but pupil size alone cannot diagnose ADHD.
What is pupillometry?
Pupillometry is the measurement of pupil size and movement, often using specialised eye-tracking equipment.
What did the Indian ADHD study find?
The 2026 IIIT-Delhi study found that trial-level pupil dynamics provided complementary information about variability and task performance in children with ADHD.
Can eye tracking replace an ADHD assessment?
No. Eye tracking and pupillometry are research tools and should not replace a comprehensive clinical ADHD evaluation.
Does ADHD medication affect pupil responses?
The 2026 study found differences in pupil dynamics between on- and off-medication conditions, although the researchers noted that medication effects could not be fully separated from other session effects.
