Switching attention within and between objects: The role of subjective organization

An object effect refers to faster and/or more accurate responses to targets when they are part of a single object than when they are parts of two different objects (Duncan, 1984). Egly, Driver, and Rafal (1994) recently showed that switching attention within an object is faster than switching attention between objects. In the experiments reported here, an object effect was found if a stimulus pattern was subjectively organized into two objects, but disappeared if the same pattern was seen as a single object. The study provides converging evidence to the existence of multiple levels of visual representations. It suggests that attention selects the internal representation of both space and object, and that subjective organization is an important factor in the manifestation of the object effect.