Abstract
This study explores the size of the attentional window, when attention is narrowly focused, with a measurement that is independent of performance - pupillary response to light. Previous studies demonstrated that when spatial covert attention is deployed to a bright area the pupil contracts relative to when attention is deployed to a dark area, even though display luminance levels are identical. We used these attentional modulations of the pupillary response to light to assess the spread of attention. Specifically, we examined how far light/dark task-irrelevant disks can be from the attended target and still lead to changes in pupil size. We presented a rotating T inside two squares, at an eccentricity of 6.75° to the right and left of fixation. Four task-irrelevant disks surrounded each square with varying inter-stimuli distances (1°, 4°, 7° and 11°). The luminance of the disks was bright on one side of the fixation and dark on the other. A central cue instructed observers to attend the right or left T and to count the number of times it assumed an upright orientation. With the three shorter distances, pupil size was smaller when the target was surrounded by bright than dark disks. Critically, this attentional effect on the pupillary response to light was eliminated at the largest distance. The results suggest that disks that were presented up to a distance of 7º fell within the attentional window. Moreover, the magnitude of the attentional modulation of the pupillary response to light decreased as the inter-stimuli distance increased suggesting that attention is not uniformly spread across the attentional window.
Meeting abstract presented at VSS 2017