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Shira Tkacz-Domb, Wolfgang Einhäuser, Yaffa Yeshurun; Pupillometric measurements reveal the characteristics of the attentional window. Journal of Vision 2020;20(11):1306. doi: https://doi.org/10.1167/jov.20.11.1306.
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© ARVO (1962-2015); The Authors (2016-present)
We examined whether the minimal size of the attentional window (i.e., its size when attention is narrowly focused) scales with eccentricity and whether it is affected by task difficulty, using attentional modulations of the pupillary light response (PLR) - pupillary constriction when covertly attending a bright area relative to attending a dark area. First, we presented rotating Ts to the right and left of fixation, surrounded by either bright or dark task-irrelevant disks with varying distances from each T. The Ts appeared at an eccentricity of 3.5° (distances: 0.5° and 1°) or 6.5° (distances: 1° and 2°). A precue indicated which T to attend, and the task was to count the number of times the T was upright. In Experiment 1, stimuli size increased with eccentricity. We found attentional modulation of the PLR with a larger target-disks distance at the far than near eccentricity, suggesting a smaller window at the near eccentricity. In Experiment 2, stimuli size was fixed, regardless of eccentricity. We found attentional modulations of the PLR with all distances. Taken together, the results suggest that the window does not scale with eccentricity, but rather depends on stimulus size. In Experiment 3, six letters appeared on a central disk of which one was the target. The task was to identify the target. In the easy condition, the non-target letters were homogenous (low load). In the hard condition, they were heterogeneous (high load). Peripheral distracting letters appeared to the right and left of fixation on disks whose luminance changed sinusoidally from bright to dark at a frequency of 1.2 Hz. The amplitude spectrum of the pupil signal shows a larger amplitude at the disk frequency of 1.2Hz in the easy as compared to the hard condition. This suggests that the attentional window was wider in the easy condition.
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