Broadening of Attention Dilates the Pupil

Abstract

Inconclusive evidence suggests that the pupil is more dilated when the breadth of attention is broad compared to narrow. To further investigate this relationship, we recorded pupil size from healthy volunteers while inducing trial-wise changes in breadth of attention. Specifically, we used a shape discrimination task to induce a narrow or broad breadth of attention by asking participants to remember the location of a gap in a small or a large circle. A visual search task with targets presented at different distances from the centre of the screen was used to behaviourally assess the success of the manipulation of breadth of attention. Data were analysed using a generalized additive mixed model to test the experimental effects on pupil size after controlling for the effects of gaze location and eye vergence. The results showed that the pupil was more dilated in the broad-breadth-of-attention condition than in the narrow-breadth-of-attention condition. However, the effect of attentional breadth on visual search performance was not mediated by pupil size, suggesting that more research is needed to understand the functional role of pupil dilation in relation to breadth of attention.

Emphasis on peripheral vision is accompanied by pupil dilation

“…We measured pupil size in anticipation of the target. In doing so, we made sure that task difficulty (reflected both in accuracy and RTs), gaze position, and visual input (including luminance and contrast)—factors that are known to influence pupil size—were kept constant across conditions, which is a crucial improvement over previous studies that addressed this question (Brocher et al, 2018; Daniels et al, 2012; Klatt et al, 2021; Kolnes et al, 2022).…”

“…This question has been addressed already in a number of studies (Brocher et al, 2018; Daniels et al, 2012; Klatt et al, 2021; Kolnes et al, 2022); for example, in a series of experiments conducted by Brocher and colleagues (2018; Klatt et al, 2021), participants were exposed to a varying number of target stimuli presented laterally at various levels of eccentricity (12.5°, 27.5°, and 42.5°) relative to a central fixation dot. Prior to the presentation of the targets, participants received a cue that informed them of the eccentricity of the upcoming targets; this served as a manipulation of attentional breadth.…”

“…Even though their results suggested that pupil size increased with increasing attentional breadth, it was not mentioned if the cues were counterbalanced, which is important in order to disentangle the effect of visual stimulation on pupil responses from the effect of attentional breadth per se. Finally, in a very recent study, Kolnes and colleagues (2022) manipulated attentional breadth by cueing participants’ attention either to a small or a large circular rim at different eccentricities (near and far), and asked them to remember the location of a gap in the cued rim. Following this task, a visual search task was used to behaviorally assess the manipulation of attentional breadth; the task consisted of stimuli spread over various eccentricities, and participants searched for a target stimulus that was oriented differently from the other stimuli.…”

“…Consistent with the above-mentioned studies, they found that pupil size increased with increasing attentional breadth (i.e., when the large rim was cued). Even though Kolnes and colleagues (2022) aimed to carefully control for common confounds (visual input and gaze position), it remained unclear if auditory cues, used to induce different levels of attentional breadth, were counterbalanced; again this is crucial because not only visual, but also auditory, stimuli have an effect on the pupil (Gingras et al, 2015). In addition, task difficulty was not controlled between conditions, although in this case the task was easier, rather than more difficult, for the far eccentricity as compared to the near eccentricity (i.e., opposite to the paradigm used by Brocher et al, 2018; Klatt et al 2021).…”

Emphasis on peripheral vision is accompanied by pupil dilation

“…Several studies have examined the relationship between attentional breadth and pupil size (Brocher et al, 2018;Daniels et al, 2012;Klatt et al, 2021;Kolnes et al, 2022). Brocher et al (2018) and Klatt et al (2021) presented stimuli at varying levels of eccentricity (distance from fixation), with a cue indicating the eccentricity of an upcoming target as a manipulation of attentional breadth.…”