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Alexandria C. Marino, Brian J. Scholl; The Role of Closure in Defining the ‘Objects’ of Object-Based Attention. Journal of Vision 2004;4(8):270. doi: 10.1167/4.8.270.
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© ARVO (1962-2015); The Authors (2016-present)
Many recent studies have concluded that the underlying units of visual attention are often discrete objects whose boundaries constrain the automatic spread of attention through a scene. However, relatively few studies have explored the particular stimulus cues that determine what counts as an ‘object’ of attention. Here we explore this issue in the context of the ‘two-rectangles’ stimuli previously used by many investigators. We first show, using both spatial cueing and divided-attention paradigms, that same-object advantages occur even when the ends of the two rectangles are not drawn. This is consistent with previous reports which have emphasized the importance of individual contours in guiding attention, and our study shows that such ‘line-tracing’ effects occur in these paradigms not only in uniform patterns, but also in displays which contain multiple grouping cues. In our divided-attention experiment, however, this contour-driven same-object advantage (without closure) was significantly weaker than that obtained with the standard two-rectangles stimulus (with closure) — demonstrating that contour-based processes do not account for all ‘object-based’ effects. Methodologically, our study is consistent with the idea that divided-attention paradigms are a more sensitive measure of object-based effects than spatial cueing. Theoretically, our results confirm and extend the observation that same-object advantages can be observed even without full-fledged ‘objects’. At the same time, however, these studies show that boundary closure — one of the most important cues to ‘objecthood’ per se — can directly influence attention. We conclude that object-based attention is not an all-or-nothing phenomenon: object-based effects can be independently strengthened or weakened by multiple cues to objecthood.
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