Abstract
If attention is cued to one part of an object, it is commonly found that reaction time is faster to a target stimulus appearing at an uncued location on the same object, than to a target at an equidistant location on a different object (Egly, Driver, & Rafal, 1994). This finding has been central to theories of “object-based attention” which postulate that objects, not simply locations in space, are the focus of visual attention. As such, it is inherently easier to switch attention between parts of one object than between parts of two different objects. However, Shomstein and colleagues (e.g., Shomstein & Yantis, 2002; Drummond & Shomstein, 2010) have argued that this within-object superiority is simply due to a strategic prioritization of same-object locations for visual search. In principle, within-object superiority should disappear in the absence of location uncertainty. We tested this prediction by presenting targets requiring an E/F discrimination at either an uncued location in the cued object, or an uncued location in a different object, in separate blocks. Contrary to the prediction of the prioritization hypothesis, within-object superiority was as large for separately blocked within- and between-object presentations, as for the more usual randomized conditions. The results favor an inherent advantage for within-object shifting of attention, rather than (or in addition to) strategic prioritization.