Abstract
In a recent study we demonstrated that the consequences of object-based attention (OBA) extended beyond the boundaries of the attended object into its surround. RTs to detect targets in the surround were found to vary as a function of distance from the center of mass of attended object even when distance from the cued location was held constant. The current study investigated the effect of an unattended object on the pattern of attentional facilitation across the visual scene. Participants were presented with two objects and then cued to attend to a location within one of them. Shortly after the cue, a target appeared either at the cued location (valid) or in one of four equidistant invalid locations: at a different location within the cued object (within-object), within the uncued object (between-objects), or in one of two locations outside of both objects which differed only in their average distance from the cued object (near-object, far-object). In the first two experiments the unattended object was either the same as the attended object (identical) or differed along one dimension: color, geometry, or category (non-identical). In all three experiments, between-objects targets which appeared in an identical uncued object were detected faster than those presented in a non-identical uncued object. We replicated our previous finding as RTs to the near-object targets were faster than those to the far-objects targets. Finally, we found that identical uncued objects had a far greater impact on the pattern of facilitation in the surround than non-identical objects. Taken together, this pattern of results suggests that far from being an all or none mechanism, OBA interacts with many different perceptual dimensions to give rise to a graded pattern of facilitation across a visual scene.