One way of perceptually organizing a complex visual scene is to attend selectively to information in a particular physical location. Another way of reducing the complexity in the input is to attend selectively to an individual object in the scene and to process its elements preferentially. This latter, object-based attention process was examined, and the predicted superiority for reporting features from 1 relative to 2 objects was replicated in a series of experiments. This object-based process was robust even under conditions of occlusion, although there were some boundary conditions on its operation. Finally, an account of the data is provided via simulations of the findings in a computational model. The claim is that object-based attention arises from a mechanism that groups together those features based on internal representations developed over perceptual experience and then preferentially gates these features for later, selective processing. Humans are exceptionally good at recognizing objects in natural visual scenes despite the fact that such scenes usually contain multiple, overlapping objects. One way in which individuals organize this complex input to minimize the processing load is to divide the field on the basis of spatial location and then to attend selectively to particular physical regions. This selective attentional spotlight "illuminates" areas of interest and facilitates preferential processing of information from those chosen areas (e.g., Broadbent, 1982 ;B. A. Eriksen & Eriksen, 1974 ;C. W. Eriksen & Yeh, 1985 ;Posner, 1980 ). There is now much evidence supporting this location-based selection, all of which shows that information from selected regions is processed faster and more accurately than equivalent information from unattended regions ( Posner, 1980 ;Posner, Snyder, & Davidson, 1980 ). The idea that location-based selection plays an exclusive role in organizing visual information, however, has been increasingly challenged in recent years. Studies have shown, for example, that humans can select one of two superimposed figures even when there is no spatial basis for selection ( Rock & Gutman, 1981 ) and can allocate attention to perceptual groups independent of the spatial proximity and contiguity of the component elements (e.g., Behrmann, Vecera, & McGoldrick, 1998 ;Driver & Baylis, 1989 ;Duncan, 1984 ;Kramer & Jacobson, 1991 ;Kramer & Watson, 1995 ;Lavie & Driver, 1996 ;Prinzmetal, 1981 ;Vecera & Farah, 1994 ). To account for these findings, an alternative selection process, in which attention is directed to objects, rather than to locations or unsegmented regions of space, has been proposed. This object-based mechanism, in which complex visual input is parsed into discrete units for further processing, has received considerable empirical, neuropsychological, and computational support in recent years.
Object-Based Visual AttentionAn early but compelling empirical illustration of the view that attention can be directed to objects, rather than to spatial locations per se, comes...