Attentional selection and the representation of holes and objects.

We examine whether holes (two separate cutout rectangles in a surface) appearing as if on a homogeneous background produce object-based effects similar to those observed when the same regions appear as separate items in front of that surface (commonly called objects). We used a version of the two-rectangle design described by R. Egly, J. Driver, and R. D. Rafal (1994). Viewing modified patterns through stereoscopic goggles created the perception of the rectangles as either part of the background or as foreground objects. In Experiment 1, we replicated Egly et al. when the regions were perceived as objects but not when they were perceived as holes. In Experiment 2, we included a condition where the background was split: The rectangles in the holes condition were perceived as part of two separate background regions. In this case, the object-based effects were the same as when the rectangles were foreground objects. The findings of Experiment 2 demonstrate that those of Experiment 1 were not due to depth per se, but rather to the background being treated as a single region. More importantly, these results demonstrate that identically shaped regions in the stimulus engage object-based attention differently, depending on how the regions are perceptually organized.