The Pupil Dilation Response to Auditory Stimuli: Current State of Knowledge.
Adriana A Zekveld, Thomas Koelewijn, Sophia E Kramer
PMID 30249172WHAT IT FOUND
Pupil dilation grows when sound is louder, speech is harder to understand, language is more complex, or material is harder to remember.
It can shrink when the task becomes too difficult, so it is not a simple effort score.
Key findings
01Pupil dilation tends to increase when speech is less intelligible or more degraded.
02At very difficult listening or memory levels, pupil dilation can shrink rather than keep rising.
03The pupil response is not a pure measure of one process; it also changes with motivation, emotion, fatigue, and automatic attention.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The review did not combine the studies into a single statistical estimate, and the authors state that the evidence is not meant to be conclusive. Many studies used young, highly educated participants, so the results may not apply to older adults. Different studies used different pupil measures and analysis methods, so results are hard to compare directly. Effects of age, hearing status, and other listener factors were mixed or interacted with task conditions.
Declared interests
The supplied text lists research support from a Marie-Curie Actions funder and the Amsterdam Public Health research institute. It does not report author conflicts of interest.
The easy way to misread this
Do not read pupil dilation as a ready clinical test of listening effort. The review says the response is affected by many processes and that more research is needed before individual data can be validly interpreted.