August 2009
Volume 9, Issue 8
Free
Vision Sciences Society Annual Meeting Abstract  |   August 2009
Attentional tracking of spatially extended objects: evidence for object-based competition between lateralized attentional systems
Author Affiliations
  • Jonathan Gill
    Department of Psychology, Harvard University
  • George Alvarez
    Department of Psychology, Harvard University
Journal of Vision August 2009, Vol.9, 147. doi:10.1167/9.8.147
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      Jonathan Gill, George Alvarez; Attentional tracking of spatially extended objects: evidence for object-based competition between lateralized attentional systems. Journal of Vision 2009;9(8):147. doi: 10.1167/9.8.147.

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Abstract

Previous studies have demonstrated that observers can select and track objects independently in the left and right visual field, as if separate attentional systems were engaged in each hemifield (Alvarez & Cavanagh, 2005). Like most attentional tracking experiments, this previous work required observers to track small objects, which always were contained completely within one half of the visual field. However, in real world viewing conditions, objects are often spatially extended, and some parts of an object will appear simultaneously in each hemifield. We tested how attention selects and tracks such spatially extended objects using lines that spread between the left and right hemifields (the bilateral condition) versus lines that spread across the top and bottom of either the left or right visual field (the unilateral condition). On each trial 4 bilateral lines or 4 unilateral lines were briefly presented, and 2 of them were highlighted as targets for tracking. Then all of the lines began to move. At the end of the trial, all of the lines stopped, and observers clicked on the target lines. We measured the proportion of trials on which both targets were accurately tracked. Observers tracked targets less accurately in the bilateral condition (64%) than in the unilateral condition (76%, p [[lt]].01). The number of target lines, and the spatial extent of the lines were equal in the two conditions. Thus, these results suggest that the critical factor is whether the targets were contained within one half of the visual field, or extended across the left and right hemifields. The difficulty of tracking objects that extend across the left and right hemifields could reflect object-based competition between the attentional systems engaged in the left and right hemifields.

Gill, J. Alvarez, G. (2009). Attentional tracking of spatially extended objects: evidence for object-based competition between lateralized attentional systems [Abstract]. Journal of Vision, 9(8):147, 147a, http://journalofvision.org/9/8/147/, doi:10.1167/9.8.147. [CrossRef]
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