Abstract
The abrupt appearance of a perceptually new object captures attention. It has been proposed that the large number of featural changes that accompany the onset of the new object are what draws attention (Thomas & Luck, 1999). In the limit, this proposal is indistinguishable from the suggestion that the ‘newness’ of the object is what captures attention (Yantis, 1993), because it is possible that the visual system treats a modified ‘old’ object as a new object when the changes to the object are too great to sustain object identity. Our first experiment assess the magnitude of featural change to a perceptually ‘old’ object (in this case, a change in luminance) required for the visual system to assume the presence of a new perceptual object rather than a change to an ‘old’ object. In the second experiment, we examine the minimum ‘object strength’ required for a new object to capture attention, which is comparatively much smaller than the magnitude of change required for the modification of an existing object to capture attention. In our third experiment, we show that ecologically implausible changes to an existing object (polarity change in conjunction with contrast change) lead to capture at a much smaller magnitude of change than do ecologically plausible changes. The final experiment examines the perceptual age at which changes to an existing object are either incorporated into the perceptual emergence of the object or are interpreted as changes to an already established object. The findings from our experiments have implications for nature of objecthood in the visual system.