Baseline pupil size encodes task-related information and modulates the task-evoked response in a speech-in-noise task.
Helia Relaño-Iborra, Dorothea Wendt, Mihaela Beatrice Neagu and 3 others
PMID 36426573WHAT IT FOUND
Baseline pupil size reflects listening effort and task familiarity, not just resting state.
In a speech-in-noise task, baselines constricted as trials progressed and differed by noise type. Ignoring baseline changes distorts how we interpret pupil dilation as a measure of cognitive load.
Key findings
01Baseline pupil size significantly decreased across trials, blocks, and sessions, indicating that time-on-task affects the resting pupil diameter during listening tasks.
02Baseline pupil size was significantly lower for speech-shaped noise compared to four-talker babble, even though peak dilation did not differ between these noise types.
03Elevated baseline pupil size significantly reduced the slope, curvature, and delay of the task-evoked pupillary response, challenging the assumption that baseline and response are independent.
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 a block design where conditions were presented in fixed blocks, which may have influenced the observed time-on-task effects. The analysis was limited to speech-in-noise tasks in normal-hearing listeners, so findings may not generalize to other populations or tasks. The growth curve analysis model used assumes specific polynomial behaviors and may not capture all nuances of the pupillary response.
Declared interests
The authors declared no potential conflicts of interest. The work was supported by the William Demant Foundation.
The easy way to misread this
Do not assume baseline pupil size is a neutral starting point. It changes with time-on-task and noise type, and these changes directly influence the interpretation of task-evoked dilation. Treating baseline as independent can lead to incorrect conclusions about listening effort.