On the Relationship between Space- and Object-Based Attention

Visual attention research has suggested two distinct and complementary forms of selection: space- and object-based attention. Though attention can be allocated to regions of space as well as perceptual objects, the exact relationship between the two modes of selection is not fully understood yet. Egly, Driver, and Rafal (1994) first demonstrated spatial- and object-based effects within a single paradigm. However, the space- and object-based reference frames overlapped—targets appeared at the cued location inside the cued object on a large majority of trials. The present study dissociated object and location using a variant of the Egly paradigm. Participants performed a shape discrimination task (T- versus L-shaped stimuli) in which the target appeared at a cued or uncued location inside a cued or uncued object. The cue denoted object, but not spatial, validity. We found both spatial- and object-cueing effects, as well as an interaction between spatial and object validity—the object-based effect occurred at both uncued and cued locations, but was smaller when the spatial location was cued. The results suggest that selection is fundamentally location based, which occurs automatically even under conditions of high object validity.