The time course of cognitive effort during disrupted speech

Listeners often find themselves in scenarios where speech is disrupted, misperceived, or otherwise difficult to recognise. In these situations, many individuals report exerting additional effort to understand speech, even when repairing speech may be difficult or impossible. This investigation aimed to characterise cognitive efforts across time during both sentence listening and a post-sentence retention interval by observing the pupillary response of participants with normal to borderline-normal hearing in response to two interrupted speech conditions: sentences interrupted by gaps of silence or bursts of noise. The pupillary response serves as a measure of the cumulative resources devoted to task completion. Both interruption conditions resulted in significantly greater levels of pupil dilation than the uninterrupted speech condition. Just prior to the end of a sentence, trials periodically interrupted by bursts of noise elicited greater pupil dilation than the silent-interrupted condition. Compared to the uninterrupted condition, both interruption conditions resulted in increased dilation after sentence end but before repetition, possibly reflecting sustained processing demands. Understanding pupil dilation as a marker of cognitive effort is important for clinicians and researchers when assessing the additional effort exerted by listeners with hearing loss who may use cochlear implants or hearing aids. Even when successful perceptual repair is unlikely, listeners may continue to exert increased effort when processing misperceived speech, which could cause them to miss upcoming speech or may contribute to heightened listening fatigue.