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Miranda Scolari, Sean O'Bryan; Phasic pupillary response modulates object-based attentional prioritization. Journal of Vision 2020;20(11):1278. doi: https://doi.org/10.1167/jov.20.11.1278.
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Visual attention studies have demonstrated that the shape of space-based selection can be governed by salient object contours: when a portion of an enclosed space is cued, the selected region extends to the full enclosure. Although this form of object-based attention (OBA) is well-established, one continuing investigation focuses on whether this selection is automatic or under voluntary control. We attempt to dissociate between these alternatives by measuring phasic changes in pupil diameter—known to fluctuate with top-down attention—during a classic two-rectangle paradigm. An endogenous spatial pre-cue directed voluntary space-based attention (SBA) to one end of a rectangular frame. We manipulated the reliability of the cue, such that targets appearing at an uncued location within the frame occurred at low or moderate frequencies. OBA effects were only marginally observed when reliability of the spatial cue was low (and hence, uncued targets were moderate), and consistent with previous findings, attention selection was primarily driven by probabilistic prioritization. These results run counter to the predictions of an automatic spread account. Next, we examined pupil size time-locked to the cue display, which was expected to reflect top-down processing of the spatial cue. We reasoned that if OBA is controlled analogously to SBA, then object selection should emerge only when it is behaviorally expedient and when phasic pupil size reflects a high degree of top-down attention to the cue display. Our results bore this out. Thus, we conclude that OBA was voluntarily controlled, and furthermore show that pupil diameter may be used to interrogate attentional strategy.
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