Pupil Size Sensitivity to Listening Demand Depends on Motivational State

Abstract

Motivation plays a role when a listener needs to understand speech under acoustically demanding conditions. Previous work has demonstrated pupil-linked arousal being sensitive to both listening demands and motivational state during listening. It is less clear how motivational state affects the temporal evolution of the pupil size and its relation to subsequent behavior. We used an auditory gap detection task (N = 33) to study the joint impact of listening demand and motivational state on the pupil size response and examine its temporal evolution. Task difficulty and a listener’s motivational state were orthogonally manipulated through changes in gap duration and monetary reward prospect. We show that participants’ performance decreased with task difficulty, but that reward prospect enhanced performance under hard listening conditions. Pupil size increased with both increased task difficulty and higher reward prospect, and this reward prospect effect was largest under difficult listening conditions. Moreover, pupil size time courses differed between detected and missed gaps, suggesting that the pupil response indicates upcoming behavior. Larger pre-gap pupil size was further associated with faster response times on a trial-by-trial within-participant level. Our results reiterate the utility of pupil size as an objective and temporally sensitive measure in audiology. However, such assessments of cognitive resource recruitment need to consider the individual’s motivational state.

Neurophysiology of effortful listening: Decoupling motivational modulation from task demands

“…Moreover, pupil size dynamics during high listening demands are now known to be modulated by an individual's motivational state (Bijleveld et al, 2009;Zhang et al, 2019); recently confirmed by us using highly-controlled noise stimuli (Kraus et al, 2023a) as in the present study's experimental paradigm. This motivation-driven additional cognitive investment indexed by pupil dilation predicted better behavioral outcomes (Kraus et al, 2023a).…”

“…Similar to our previous approach (Kraus et al, 2023a), we investigated whether a smaller pupil size is associated with an increased probability that a participant misses a gap or responds slower to the gap.…”

“…The motivational state of a person influences whether they are willing to invest cognitively in demanding listening contexts (Brehm & Self, 1989; Kraus et al, 2023a; Richter et al, 2016). That is, a person who sees no intrinsic (e.g., enjoyment) or extrinsic (e.g., financial) value in listening, and is thus in a low motivational state, may be more likely to disengage from listening than someone who is highly motivated, especially under highly demanding conditions (Brehm & Self, 1989; Herrmann & Johnsrude, 2020; Pichora-Fuller et al, 2016; Richter et al, 2016).…”

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

“…However, pupil size can vary due to factors unrelated to task demands, such as changes in light (Knapen et al, 2016;Suzuki et al, 2019;Thurman et al, 2021) or in the angle of the eye relative to the eye-tracking camera (Brisson et al, 2013;Hayes and Petrov, 2016;Fink et al, 2021). To address the latter, individuals typically maintain fixation on a point on a computer monitor (Zekveld et al, 2018;Winn and Teece, 2021;Kraus et al, 2023a), but restriction of gaze can reduce memory and mental imagery (Johansson et al, 2012).…”

“…However, pupil size can vary due to factors unrelated to task demands, such as changes in light (Knapen et al, 2016; Suzuki, Minami, Laeng, & Nakauchi, 2019; Thurman et al, 2021) or in the angle of the eye relative to the eye-tracking camera (Brisson et al, 2013; Fink et al, 2023; Hayes & Petrov, 2016). To address the latter, individuals typically maintain fixation on a point on a computer monitor (Kraus, Obleser, & Herrmann, 2023; Matthew B. Winn & Teece, 2021; Adriana A.…”