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Alex White, Brian Scholl; Inattentional blindness, object persistence, and Foveal inhibition. Journal of Vision 2007;7(9):540. doi: 10.1167/7.9.540.
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© ARVO (1962-2015); The Authors (2016-present)
The importance of attention for conscious perception is especially clear in inattentional blindness (IB) — the failure to consciously perceive salient unexpected objects (UOs) when attention is otherwise engaged. Surprisingly, IB is especially severe for UOs that appear at fixation — literally right in front of your eyes — compared to peripheral UOs. This effect has been explained by especially strong foveal inhibition when observers' attention is directed to the periphery. Because these experiments included a fixation mark, however, the visual system may instead have interpreted the UO not as a new object, but as a sudden change to the features of the fixation mark itself. Such interpretations may be automatically computed in mid-level vision, where object persistence is driven primarily by spatiotemporal factors rather than surface features. Observers in our tests of these explanations fixated centrally and had to judge which arm of a briefly presented (and masked) peripheral cross was longer. After three trials, a salient UO at fixation was presented along with the cross. The key manipulation involved the fixation mark, which was either a small cross (which was then completely replaced by the UO), or a much larger cross formed by two diagonal lines that spanned the entire display. If enhanced IB at fixation is due to the representation of persisting objects despite featural change, then less IB should be observed with the global fixation mark. In fact, however, IB in both conditions was dramatic (though not at ceiling) and did not differ — even with twice as many observers as in other studies. We conclude that parafoveal attention may indeed require especially strong foveal inhibition, with severe consequences for conscious awareness. However, the existence of foveal inhibition does not rule out independent effects of object persistence on IB, as explored in additional studies of appearance vs. disocclusion.
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