Look Me in the Eye: Proving Auditory Processing Disorder Is Physiologically Real (and Should Be Included in DHH)
One of the biggest challenges with auditory processing disorder (APD) is that we’re still stuck treating it like a behavioral or educational issue—not a medical one.
The standardized tests we use to diagnose APD are entirely behavioral. A child is asked to repeat words in noise, track tones, or follow verbal instructions. These are functional, yes—but they rely heavily on attention, language, and task performance. So when a child struggles, it’s easy for people to assume the issue is attention, motivation, or learning—not how their brain is actually processing sound.
And to make matters worse, there is no gold standard for APD testing.
The batteries vary wildly from clinic to clinic, subtracting even more credibility from the diagnosis in the eyes of schools, insurance companies, and even other clinicians.
Meanwhile, a swarm of adjacent professionals—SLPs, OTs, and psychologists—circle around the edges, each interpreting the symptoms through their own lens. And because APD has no firm physiological marker, these symptoms often get mislabeled as the cause, rather than being recognized as correlated effects of underlying auditory dysfunction.
Compare that to auditory neuropathy spectrum disorder (ANSD). ANSD affects the transmission of sound between the ear and the brain. And even though it sometimes presents with normal audiograms, it’s still recognized as a physiological condition.
We have objective tests—acoustic reflexes and auditory brainstem response (ABR)—that can often help confirm the diagnosis, at least when the auditory neuropathy is substantial enough to show up clearly.
And unlike APD, kids with ANSD are more likely to be treated with dignity. They qualify for Deaf and Hard of Hearing services. Because it is understood as a physiological issue, their access needs are often taken far more seriously.
But kids with APD? They’re often labeled as inattentive or academically struggling.
Instead of being seen as children with legitimate auditory access issues, they’re frequently routed into categories like Other Health Impairment (OHI), Speech-Language, or general education with no recognition of the sensory deprivation they’ve experienced.
Kids with APD often get blamed for poor behavior.
Instead of being seen as having a real auditory access issue, they’re labeled as inattentive, unmotivated, defiant, or learning disabled—when in fact, they’re missing critical parts of language and instruction due to how their brain processes sound.
And the only reason why? We don’t have electrophysiological testing that goes high enough into the brain to prove it’s real.
We can measure sound getting to the ear. We can measure it reaching the brainstem. But when it comes to the cortex—where sound turns into meaning, where language is built—we’re mostly guessing.
Without standardized tools to show what’s happening in those higher-level brain systems, APD keeps getting dismissed as effort, attitude, or learning style.
That’s not science. That’s a gap in tools.
It’s like watching a whitewater river and trying to understand its chaos just by looking at the surface. You can describe the spray, the noise, the churn—but until you look beneath the surface and see the rocks on the riverbed, you won’t really understand why the water moves the way it does. You’re just reacting to the symptoms.
If you could map those rocks—those neurological bottlenecks—you could start predicting the turbulence and maybe even clearing a better path.
But even if you smooth out that part of the river, you still have to watch for new obstacles downstream: a dam built by a teacher who won’t provide accommodations, a school that ignores the diagnosis, a system that dismisses the entire condition because it’s not visible on an audiogram.
So while understanding the brain is critical, it’s not the whole story.
We also need to recognize the barriers that appear after the diagnosis—the ones that aren’t neurological, but structural, cultural, and educational. And those can cause just as much damage.
That’s what pupillometry and physiological testing offer us: a chance to stop blaming the water and start examining the rocks—and hopefully, help clear the river ahead too.
We also need to start seriously including fatigue in our assessments of APD.
That means both subjective tools, like validated listening fatigue rating scales, and objective tools, like real-time pupillometry. The effort it takes to listen—especially in noise—can wear a child down over the course of the school day. When we fail to measure that, we miss the cumulative burden APD places on children, and we underestimate its true impact.
This is exactly why we need better tools—because behavior alone is not enough to understand what’s really happening in the brain. And that brings us to a parallel conversation that’s already gaining traction in a different but related space:
ADHD.
Just like APD, ADHD has long been treated primarily as a behavioral diagnosis, with symptoms interpreted through observation and checklists. But new research is starting to challenge that assumption—not by throwing away behavior, but by anchoring it to measurable physiology.
A study published in npj Digital Medicine (Choi et al., 2025) explored whether ADHD could be identified not just behaviorally, but physiologically—by analyzing retinal images.
Researchers used AI to detect structural differences in the back of the eye—blood vessel patterns and optic disc changes—that were correlated with ADHD.
Their model achieved nearly 97% accuracy using nothing more than photos of the retina. These were kids already diagnosed with ADHD through conventional methods. The imaging didn’t replace behavior—it validated it with biology.
It’s a promising example of what might be possible for APD in the future—but it’s far from being standard practice.
And while it’s progress, ADHD is still mostly treated as a behavioral diagnosis.
Pediatricians are now diagnosing it during short office visits, often based on school behavior reports. Teachers may push for medication, and parents are left to navigate stigma, side effects, and treatment plans with little clarity.
It’s not that ADHD isn’t real—it’s that the lack of reliable, physiological data still leaves room for misunderstanding and over-labeling.
And we need the same kind of progress for APD—without falling into the same traps.
Pupillometry is one way forward.
When the brain is working harder—especially to make sense of sound in noise—the pupil dilates. That change in pupil size happens automatically and reliably, and it correlates with listening effort. You can literally watch the brain go into strain mode.
And this isn’t a brand-new idea.
Researchers have been exploring the use of pupil response as an indicator of effortful listening for over a decade.
A 2010 study by Zekveld and colleagues clearly showed that pupil dilation increases as sentence intelligibility decreases—indicating greater cognitive effort during degraded speech.
In other words, the harder it is to understand what you’re hearing, the bigger the physiological response.
This is the kind of data that could have huge implications for children with APD, who often appear “fine” on basic hearing tests but are working twice as hard to keep up.
More recent work (Winn & Teece, 2021) has confirmed that kids with auditory processing challenges show increased pupil response, especially in speech-in-noise conditions.
The beauty of pupillometry is that it doesn’t require sedation or expensive machines. It can be done with a standard camera, good lighting, and a well-designed listening task.
And it gives us real-time, noninvasive, objective data on listening effort—even when behavioral scores are inconclusive.
Some researchers have also explored the P300 auditory evoked potential, a long-latency brainwave that reflects the brain’s reaction to a stimulus that is unexpected or different—a kind of “oddball” response.
In theory, it shows whether the brain detected a meaningful change in sound, like a pitch shift or a rare tone among many.
But that’s also its limitation.
The P300 doesn’t measure understanding. It just shows that the brain noticed a change. It tells us the person heard something different, but not how clearly they understood it or how much effort it took to process.
Consider this: if APD were just a behavioral or motivational issue, why would pupillometry consistently show increased listening effort in harder-to-discern auditory conditions?
The brain doesn’t dilate the pupil for no reason.
These children are working harder because their neurological systems are working differently.
The struggle is real—and it’s physiological.
We just haven’t been measuring it properly.
That’s why pupillometry matters.
The pupil tells us how hard the brain is working in real time. It shows processing load, not just sensory detection.
And that distinction matters.
Because performance doesn’t always reflect effort. A child might ace a test but be completely drained—and no one notices.
When combined with behavioral testing, pupillometry offers a way to bridge the gap.
It helps us move APD from a misunderstood behavioral diagnosis into the same physiological category where ANSD and hearing loss already live.
And when schools and clinicians can see objective evidence of effort and strain, they’re far more likely to treat the diagnosis seriously—and provide the accommodations these kids deserve.
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References
Choi, H., Hong, J., Kang, H. G., Park, M.-H., Ha, S., Lee, J., Yoon, S., Kim, D., Park, Y. R., & Cheon, K.-A. (2025). Retinal fundus imaging as biomarker for ADHD using machine learning for screening and visual attention stratification. npj Digital Medicine, 8, Article 164.
Winn, M. B., & Teece, K. H. (2021). Pupillary response to listening effort during a concurrent memory task. Journal of Speech, Language, and Hearing Research, 64(2), 399–411.
Zekveld, A. A., Kramer, S. E., & Festen, J. M. (2010). Pupil response as an indication of effortful listening: The influence of sentence intelligibility. Ear and Hearing, 31(4), 480–490.
Duarte, J. L., Alvarenga, K. F., Banhara, M. R., & Costa Filho, O. A. (2009). P300 long-latency auditory evoked potential in normal hearing subjects: Simultaneous recording value in Fz and Cz. Brazilian Journal of Otorhinolaryngology, 75(1), 35–40.
