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Light level, SNR, and the pupil response (Baldock et al., 2024)

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posted on 2024-05-01, 13:23 authored by Jennifer Baldock, Sarosh Kapadia, Willem van Steenbrugge, Jason McCarley

Purpose: There is increasing interest in the measurement of cognitive effort during listening tasks, for both research and clinical purposes. Quantification of task-evoked pupil responses (TEPRs) is a psychophysiological method that can be used to study cognitive effort. However, light level during cognitively demanding listening tasks may affect TEPRs, complicating interpretation of listening-related changes. The objective of this study was to examine the effects of light level on TEPRs during effortful listening across a range of signal-to-noise ratios (SNRs).

Method: Thirty-six adults without hearing loss were asked to repeat target sentences presented in background babble noise while their pupil diameter was recorded. Light level and SNRs were manipulated in a 4 × 4 repeated-measures design. Repeated-measures analyses of variance were used to measure the effects.

Results: Peak and mean dilation were typically larger in more adverse SNR conditions (except for SNR −6 dB) and smaller in higher light levels. Differences in mean and peak dilation between SNR conditions were larger in dim light than in brighter light.

Conclusions: Brighter light conditions make TEPRs less sensitive to variations in listening effort across levels of SNR. Therefore, light level must be considered and reported in detail to ensure sensitivity of TEPRs and for comparisons of findings across different studies. It is recommended that TEPR testing be conducted in relatively low light conditions, considering both background illumination and screen luminance.

Supplemental Material S1. Example sentence list and scoring sheet.

Supplemental Material S2. Linear mixed-effects model to account for the influence of baseline.

Supplemental Material S3. Post hoc simple effects analyses for peak dilation – light level as grouping variable.

Supplemental Material S4. Post hoc simple effects analyses for peak dilation – SNR as grouping variable.

Baldock, J., Kapadia, S., van Steenbrugge, W., & McCarley, J. (2024). The effects of light level and signal-to-noise ratio on the task-evoked pupil response in a speech-in-noise task. Journal of Speech, Language, and Hearing Research. Advance online publication.


This research was supported by the Australian Government Research Training Program Scholarship, The Ember Venning Scholarship, and Research Student Maintenance Funding through Flinders University.