Listening Effort Is Not the Same as Speech Intelligibility Score.
Matthew B Winn, Katherine H Teece
PMID 34261392WHAT IT FOUND
Nearly perfect intelligibility scores can hide effortful mental correction.
When words were distorted, listeners' pupils dilated more despite 99.2% correct responses. In cochlear implant users, pupil dilation tracked nonsense responses more than error count.
Key findings
01Experiment 1 listeners repeated sentences with 99.2% word accuracy, yet pupil dilation was larger when a target word was distorted by noise or mispronunciation than when it was intact.
02In Experiment 2, the number of errors within a sentence did not reliably increase pupil dilation; responses that were linguistically incoherent did.
03Errors among words earlier in the sentence led to a much larger change in pupil dilation, and when an early error had already occurred, an additional error on the final word was associated with reduced pupil dilation.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The samples were small: 20 normal-hearing listeners and 19 cochlear implant users, and the task was laboratory sentence repetition, not everyday conversation. Experiment 1 participants were not evaluated for visual acuity, although lighting was kept constant to reduce pupillary light reflex effects. Experiment 2 was a post hoc reanalysis with many comparisons and unbalanced error types, so the patterns should be read as exploratory. It cannot be known whether correct responses were truly perceived correctly or were mentally corrected, especially in Experiment 2. Pupil dilation is an indirect measure of effort; the paper does not show that it can be used as a clinical assessment or that reducing effort improves function. Two-thirds of Experiment 1 stimuli required correction, which may have raised overall engagement.
Declared interests
The authors declared no potential conflicts of interest. The supplied metadata lists NIH extramural research support.
The easy way to misread this
Do not conclude that speech intelligibility scores are clinically useless or that pupil dilation can diagnose listening effort. The study was a small laboratory task, and Experiment 2 was exploratory; it shows that effort and word accuracy scores can diverge, not that standard tests should be abandoned.