Pupil dilation and microsaccades provide complementary insights into the dynamics of arousal and instantaneous attention during effortful listening

Abstract

Listening in noisy environments requires effort - the active engagement of attention and other cognitive abilities, as well as increased arousal. The ability to separately quantify the contribution of these components is key to understanding the dynamics of effort and how it may change across listening situations and in certain populations. We concurrently measured two types of ocular data in young participants (both sexes) - Pupil dilation (PD) (thought to index arousal aspects of effort) and Microsaccades (MS) (hypothesized to reflect automatic visual exploratory sampling) whilst listeners were performing a speech-in-noise task under high- (HL) and low- (LL) perceptual load conditions. Sentences were manipulated so that the behaviourally relevant information (keywords) appeared at the end (Exp1) or beginning (Exp2) of the sentence, resulting in different temporal demands on focused attention. In line with previous reports, PD effects were associated with increased dilation under load. We observed a sustained difference between HL and LL conditions, consistent with increased phasic and tonic arousal. Importantly we show that MS rate was also modulated by perceptual load, manifested as a reduced MS rate in HL relative to LL. Critically, in contrast to the sustained difference seen for PD, MS effects were localised in time, specifically during periods when demands on auditory attention were greatest. These results demonstrate that auditory selective attention interfaces with the mechanisms controlling MS-generation, establishing MS as an informative measure, complementary to PD, with which to quantify the temporal dynamics of auditory attentional processing under effortful listening conditions.

Pupil size and eye movements differently index effort in both younger and older adults

“…Eye movements reflect listening challenges differently than the pupil size Recent works suggest that reductions in eye movements may index effort. Eye movements decrease when individuals perform a high-load compared to a low-load memory task (Lipton et al, 1980;Hutton and Tegally, 2005;Kosch et al, 2018;Walter and Bex, 2021) and when speech masking increases (Contadini-Wright et al, 2023;Cui and Herrmann, 2023). We also found that gaze dispersion decreased with decreasing SNR (Figures 2, 4, and 5), and extend this previous work by showing that the sensitivity of eye movements to changes in speech masking does not differ between younger and older adults.…”

“…Gaze dispersion is a broad measure that captures any eye movements. Analyses of saccades (including microsaccades) require setting a velocity threshold to determine what counts as a saccade (Engbert and Kliegl, 2003;Engbert, 2006;Widmann et al, 2014;Kadem et al, 2020;Contadini-Wright et al, 2023;Cui and Herrmann, 2023), but the threshold can influence whether or not effects of cognition on saccades can be observed (Cui and Herrmann, 2023). Nonetheless, we explored the sensitivity of saccades to changes in SNR and results were very similar to the results for gaze dispersion.…”

“…Recent work suggests that the quantification of eye movements may provide an alternative effort metric. Eye movements decrease during periods of high compared to low memory load (Kosch et al, 2018;Walter and Bex, 2021) and with increasing speech masking (Contadini-Wright et al, 2023;Cui and Herrmann, 2023). This research has focused mainly on increases in effort as task demands increase.…”

Effort cost of harvest affects decisions and movement vigor of marmosets during foraging

“…Some of these neurons show a transient change in their activity when acquisition of reward requires expenditure of physical effort (Bornert and Bouret, 2021). However, the link between effort costs and pupil size appears to go beyond motor control, as a recent paper found that pupil size increases during effortful speech perception (Contadini-Wright et al, 2023). Thus, although in our work increases in pupil size were always associated with increased movement vigor, the results from other studies suggest that economic variables such as cognitive effort in tasks in which there is no concomitant movement also drive an increase in pupil size.…”

Cross-modal interactions between auditory attention and oculomotor control

“…Gradual changes in sustained MS incidence have been consistently associated with the attentional load experienced by individuals (Pastukhov and Braun, 2010; Benedetto et al, 2011; Siegenthaler et al, 2014; Widmann et al, 2014; Dalmaso et al, 2017; Lange et al, 2017; Yablonski et al, 2017; Abeles et al, 2020; Badde et al, 2020; Contadini-Wright et al, 2023). For instance, MS rate gradually reduces in anticipation, and during the processing of predictable behavioural targets (Abeles et al, 2020; Contadini-Wright et al, 2023).…”