The Relation Between Sustained Listening Effort and Fatigue

Abstract This study investigated whether sustained listening effort contributes to measurable changes in fatigue, understood here as a decline in performance and/or motivation to sustain effort over time, and to sleepiness, defined as a physiological state indexed by spontaneous pupil fluctuations. We further evaluated whether the Pupil Unrest Index (PUI) can serve as an objective marker of these processes. Twenty young adults with normal hearing completed a dual-task paradigm with speech-on-speech masking and a memory task, tested under four acoustic processing conditions. PUI increased from pre- to post-test in most participants, with the largest rise in the most difficult (unprocessed co-located) condition. Subjective fatigue ratings also increased across sessions, though without systematic differences between conditions. Behavioral results showed sequence effects: performance declined in intermediate conditions, whereas it remained stable in the easiest and hardest conditions, suggesting that both fatigue and motivational regulation shaped outcomes. Together, these findings demonstrate that sustained listening effort is associated with increased fatigue and sleepiness. They further support the PUI as a promising objective physiological measure of listening-related fatigue, complementing subjective and behavioral assessments.