What insights into pupil size during listening do various analysis techniques provide and how sensitive are they to task demands and luminance?

Listening effort is a specific form of mental effort that occurs when a task involves listening as defined in the Framework for Understanding Effortful Listening (FUEL). The pupil dilation response is sensitive to listening effort during listening to speech in noise, it is sensitive to task demands and monetary reward. Different analysis techniques of pupil data have been proposed in the literature to provide comprehensive indicators of effort.
In this study, we assessed and compared the sensitivity of several proposed analysis techniques to auditory task demands and luminance. The techniques were applied to two independent datasets containing pupil data from normal-hearing participants recorded during Speech Reception Threshold (SRT) tests. The first dataset was recorded during an SRT with stimuli at fixed Signal-to-Noise (SNR) ratios (Ohlenforst et al. 2017). The second dataset was based on an adaptive SRT test that was performed in two luminance levels (Wang et al. 2018). Data were analysed using several techniques, including calculation of the Index of Pupillary Activity measuring pupillary oscillations and Principal Component Analysis revealing independent time components in the signal.
The results indicate that applied analyses techniques provide parameters differentially sensitive to task demand and luminance.