Abstract
In the double-rectangle cueing paradigm of Egly, Driver, Rafal (1994), one of the two oblong rectangles is cued and subsequently a target appears. Reaction time benefit is observed when the target appears on the same object as the cue, compared to when it appears on a different object (i.e., the same object effect). In this study, we manipulate the cue display and the display(s) afterwards to demonstrate that the target display rather than the cue display is crucial for object-based selection. The display was modified from that of Egly et al. by using four small rectangles during the cue presentation and introducing an occluder at different times after the cue display or concurrently with it. The occluder was presented to induce amodal completion among the four rectangles to form two oblong rectangles as in Egly et al. Our results show that the same-object effect was obtained when the occluder was presented 100 ms before the target presentation, and when the target appeared together with the occluder. The observation that there is a same-object effect when an object representation is changed, but not when an occluder is not presented, points to the importance of an on-line updating process during object-based selection. The results are discussed in the context of the three hypotheses of the mechanism of object-based attention: the spreading, prioritization, and shift hypothesis.
This study is supported by National Science Council of Taiwan (NSC94-2752-H-002-008-PAE).