Effect of Speech-to-Noise Ratio and Luminance on a Range of Current and Potential Pupil Response Measures to Assess Listening Effort.
Patrycja Książek, Adriana A Zekveld, Dorothea Wendt and 3 others
PMID 33926329WHAT IT FOUND
Pupil size changes track listening effort, but light levels interfere with most measures.
Peak and mean dilation responded to noise difficulty, yet brightness still affected them. A newer frequency-based index failed to track difficulty and was also disrupted by light, so it cannot currently separate effort from lighting.
Key findings
01Peak and mean pupil dilation increased with listening difficulty (lower signal-to-noise ratio) but were also significantly affected by luminance.
02The Index of Pupillary Activity (IPA), designed to isolate cognitive effort from light reflexes, showed no effect of listening difficulty and was significantly affected by luminance.
03Time-course analyses (GCA and PCA) detected effects of both listening difficulty and luminance across multiple stages of the pupil response.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study used pre-existing data from two different studies, which differed in quality and number of responses. Pupil data was recorded at a relatively low sampling frequency (60 Hz) and with short recordings. The interaction between SNR and luminance was not systematically manipulated, making it difficult to compare their effects directly. The study did not test whether pupil differences occurred specifically during listening, rehearsal, or response phases.
Declared interests
The authors declared no conflicts of interest. The research was supported by non-U.S. government funding.
The easy way to misread this
Do not assume that pupil dilation measures can currently be used to assess listening effort in uncontrolled environments. The study found that luminance significantly affected almost all measures, including those previously thought to be immune to light, meaning that a patient's pupil size may reflect the room brightness rather than their cognitive load.