Salience-dependent disruption of sustained auditory attention can be inferred from evoked pupil responses and neural tracking of task-irrelevant sounds

Stimulus-driven attention allows us to react to relevant stimuli (and imminent danger!) outside our current focus of attention. But irrelevant stimuli can also disrupt attention; for example, during listening to speech. The degree to which sound captures attention is called salience, which can be estimated by existing, behaviorally validated, computational models (Huang & Elhilali, 2017). Here we examined whether neurophysiological responses to task-irrelevant sounds indicate the degree of distraction during a sustained-listening task and how much this depends on individual hearing thresholds. N = 47 Danish-speaking adults (28/19 female/male; mean age: 60.1, SD: 15.9 years) with heterogenous hearing thresholds (PTA; mean: 25.5, SD: 18.0 dbHL) listened to continuous speech while one-second-long, task-irrelevant natural sounds (distractors) of varying computed salience were presented at unpredictable times and locations. Eye tracking and electroencephalography were used to estimate pupil response and neural tracking, respectively. The task-irrelevant sounds evoked a consistent pupil response (PR), distractor-tracking (DT) and a drop of target-tracking (ΔTT), and statistical modelling of these three measures within subjects showed that all three are enhanced for sounds with higher computed salience. Participants with larger PR showed a stronger drop in target tracking (ΔTT) and performed worse in target speech comprehension. We conclude that distraction can be inferred from neurophysiological responses to task-irrelevant stimuli. These results are a first step towards neurophysiological assessment of attention dynamics during continuous listening, with potential applications in hearing-care diagnostics. Significance statement Successful speech-in-noise comprehension in daily life does not only depend on the acuity of the auditory input, but also cognitive factors like attentional control. Being able to measure distraction-dependent neurophysiological responses to peripheral, task-irrelevant stimuli would enable monitoring the extent to which the attentional focus is instantaneously captured away from a target under sustained attention. Here we show that especially pupil response and neural tracking of distractor sounds reflect the degree to which people with both normal and elevated hearing thresholds are distracted. Such a measure could be used to non-invasively track the focus of attention and thus could find application in hearing care diagnostics, where cognitive factors like attentional control are being increasingly recognized as important.