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Irene Reppa, Daryl Fougnie; How does attention spread across the surface of an object oriented in depth?. Journal of Vision 2007;7(9):1075. doi: 10.1167/7.9.1075.
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Previous evidence suggests that exogenous spatial attention spreads in perceived three-dimensional (3D) space as determined by binocular disparity and occlusion. In this study we asked whether spatial attention spreads across the surface of a 3D object that is oriented in depth in terms of actual or perceived space.
To examine this question, we employed a spatial cueing paradigm in which one of four corners along the front plane of a 3D object was exogenously cued with 75% validity. On invalid trials, the target would appear in a corner adjacent to the cued corner. Importantly, on some trials we manipulated the perceived depth of the object by rotating it 45° to either the left or right. Rotation affected the actual distance (i.e. the distance between corners as drawn in 2D space) but did not affect the perceived distance. We examined whether invalid RT costs were affected by depth rotation. If attention spreads across the perceived length of a 3D object surface than invalid RT costs may be independent of the object's orientation in depth. Otherwise, invalid costs may reflect the actual distance between the cued and target locations. Depth rotation would produce smaller costs for horizontal shifts while vertical shift RTs would depend on whether the shift occurred in the close or far depth plane.
In two experiments (one with static images and a second with objects that appeared to rotate), there was no significant difference in RTs between front and rotated views for vertical or horizontal shifts. In the rotated condition, invalid RT costs were smaller in the horizontal far-to-close condition compared with the horizontal close-to-far condition, replicating previous findings. The results show that (a) attention spreads across the perceived surface space and (b) the orientation of the object in depth affects the way attention spreads across its surface.
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