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Dina Popovkina, John Palmer, Cathleen Moore, Geoffrey Boynton; Hemifield effects on divided attention for dual tasks with visual objects. Journal of Vision 2021;21(9):2172. doi: https://doi.org/10.1167/jov.21.9.2172.
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© ARVO (1962-2015); The Authors (2016-present)
Recent studies have shown a surprising hemifield effect in multiple object tracking: one can track twice as many objects in different hemifields as in a single hemifield. No such effect occurs in typical visual search tasks, but it has been reported in "multifocal" visual search, in which only some areas of the visual field are relevant. One hypothesis is that hemifield effects are specific to tasks requiring multifocal spatial attention (Alvarez, Gill, & Cavanagh, 2012, JOV). To test this hypothesis, we conducted a dual-task experiment in which observers made semantic categorizations of nameable objects. This divided attention paradigm requires multifocal spatial attention because there are separate foci for the two tasks. For each task, one must attend the task-relevant stimulus and ignore the other stimuli. Previous studies using a dual-task paradigm have shown large divided attention effects for object judgments, measured as the dual-task deficit (the difference in performance in single- and dual-task trials). In our experiment, 4 objects were presented simultaneously in separate quadrants, and participants made judgments about 1 of 4 objects (single-task trials) or 2 of 4 objects (dual-task trials). As in previous studies, there was a large dual-task deficit for object judgments. To address hemifield effects, the dual-task deficit for a unilateral condition with relevant objects within the same hemifield was compared to the dual-task deficit for a bilateral condition with relevant objects in separate hemifields. Preliminary results showed no difference in the dual-task deficits for unilateral and bilateral conditions. Unlike multiple object tracking, dual tasks revealed little or no hemifield effects for divided attention to multiple objects. These findings are not consistent with the hypothesis that such effects are specific to tasks with multifocal spatial attention.
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