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Björn Herrmann
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Journal Articles
Publisher: Journals Gateway
Journal of Cognitive Neuroscience (2024) 36 (7): 1325–1340.
Published: 01 June 2024
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The assessment of mental effort is increasingly relevant in neurocognitive and life span domains. Pupillometry, the measure of the pupil size, is often used to assess effort but has disadvantages. Analysis of eye movements may provide an alternative, but research has been limited to easy and difficult task demands in younger adults. An effort measure must be sensitive to the whole effort profile, including “giving up” effort investment, and capture effort in different age groups. The current study comprised three experiments in which younger ( n = 66) and older ( n = 44) adults listened to speech masked by background babble at different signal-to-noise ratios associated with easy, difficult, and impossible speech comprehension. We expected individuals to invest little effort for easy and impossible speech (giving up) but to exert effort for difficult speech. Indeed, pupil size was largest for difficult but lower for easy and impossible speech. In contrast, gaze dispersion decreased with increasing speech masking in both age groups. Critically, gaze dispersion during difficult speech returned to levels similar to easy speech after sentence offset, when acoustic stimulation was similar across conditions, whereas gaze dispersion during impossible speech continued to be reduced. These findings show that a reduction in eye movements is not a byproduct of acoustic factors, but instead suggest that neurocognitive processes, different from arousal-related systems regulating the pupil size, drive reduced eye movements during high task demands. The current data thus show that effort in one sensory domain (audition) differentially impacts distinct functional properties in another sensory domain (vision).
Journal Articles
Publisher: Journals Gateway
Journal of Cognitive Neuroscience (2022) 34 (6): 933–950.
Published: 02 May 2022
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Older people with hearing problems often experience difficulties understanding speech in the presence of background sound. As a result, they may disengage in social situations, which has been associated with negative psychosocial health outcomes. Measuring listening (dis)engagement during challenging listening situations has received little attention thus far. We recruit young, normal-hearing human adults (both sexes) and investigate how speech intelligibility and engagement during naturalistic story listening is affected by the level of acoustic masking (12-talker babble) at different signal-to-noise ratios (SNRs). In , we observed that word-report scores were above 80% for all but the lowest SNR (−3 dB SNR) we tested, at which performance dropped to 54%. In , we calculated intersubject correlation (ISC) using EEG data to identify dynamic spatial patterns of shared neural activity evoked by the stories. ISC has been used as a neural measure of participants' engagement with naturalistic materials. Our results show that ISC was stable across all but the lowest SNRs, despite reduced speech intelligibility. Comparing ISC and intelligibility demonstrated that word-report performance declined more strongly with decreasing SNR compared to ISC. Our measure of neural engagement suggests that individuals remain engaged in story listening despite missing words because of background noise. Our work provides a potentially fruitful approach to investigate listener engagement with naturalistic, spoken stories that may be used to investigate (dis)engagement in older adults with hearing impairment.