Emphasis on peripheral vision is accompanied by pupil dilation

Abstract

Previous studies have suggested that pupil size increases with covert shifts of attention to the peripheral as compared to the (para)foveal visual field, i.e., with increasing attentional breadth. This finding is crucial because it matches the theoretical prediction that (para)foveal vision benefits more from the visual acuity provided by small pupils than peripheral vision does. However, no study has investigated this question while controlling for all possible confounds (e.g., task difficulty). Throughout three experiments (N=100) we tested whether pupil size increases with increasing attentional breadth, and if this effect depends on the shape of attention, that is, whether attention is broadly (Annulus Attention) or narrowly (Spotlight Attention) distributed. We found that pupil size increases with covert shifts of attention to the peripheral visual field, i.e., increasing attentional breadth, with no clear difference between the two shapes of attention. We further found a correlation with performance, suggesting a functional benefit of the link between attentional breadth and pupil size. Finally, we propose that cognitively driven pupil dilation is not merely a convenient marker of activity in brain areas such as the Locus Coeruleus, but rather is an adaptive response that reflects an emphasis on peripheral vision over foveal vision.

Functional benefits of cognitively driven pupil‐size changes

“…Pupil size not only reveals whether an attended stimulus is bright or dark, as discussed in Section 2.1, but also whether the attended stimulus is in central or peripheral vision (attentional breadth; Brocher et al, 2018; Daniels et al, 2012; Klatt et al, 2021; Kolnes et al, 2022; Vilotijević & Mathôt, 2023). In our recent study (Vilotijević & Mathôt, 2023), we measured pupil size while attention was directed to concentric annuli of varying eccentricity (distance from fixation; Figure 1c). Specifically, we cued participants' covert attention to the annulus where the upcoming target would most likely (but not always) appear.…”

“…We then discuss the advantages and disadvantages associated with small and large pupils, specifically in terms of visual acuity and visual sensitivity, and how the relative weights of these (dis)advantages depend on contextual factors, such as the task and whether stimuli are presented in central or peripheral vision (Section 3). We then move on to we discuss potential functional explanations for cognitively driven pupil‐size changes, and suggest that they reflect sensory tuning: a subtle optimization of visual‐information intake that is tailored to the demands of the current situation and the immediate future (Franke et al, 2022; Mathôt, 2020; Vilotijević & Mathôt, 2023) (Section 4). Finally, we highlight open questions, notably the question of how pupil dilation as a result of mental effort is explained by sensory tuning, as well as the related question of whether sensory tuning is based on more‐or‐less fixed heuristics or rather is flexible and susceptible to top‐down control (Section 5).…”

Methods in cognitive pupillometry: Design, preprocessing, and statistical analysis

“…Throughout this paper, we will refer to an experiment that we have recently conducted as an example. The theoretical motivation and methodological details for this experiment are described in Vilotijević and Mathôt (2022) and the associated preregistration (https:// osf. io/ ma4u9).…”

Methods in Cognitive Pupillometry: Design, Preprocessing, and Statistical Analysis

“…in Vilotijević and Mathôt (2022) and the associated preregistration (https://osf.io/ma4u9). Here, we will limit ourselves to those aspects of the experiment that generalize to many other experiments.…”

“…Throughout this paper, we will refer to an experiment that we have recently conducted as an example. The theoretical motivation and methodological details for this experiment are described in Vilotijević and Mathôt (2022) and the associated preregistration (https://osf.io/ma4u9). Here, we will limit ourselves to those aspects of the experiment that generalize to many other experiments.…”