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Abstract:
Abstract: Visual attention alters perception in several
quantitative and qualitative ways. To characterize the different
perceptual consequences of attention, we compare "attentive vision"
with the "ambient vision" that remains with poor attention. Ambient
vision is surprisingly robust and supports discrimination
performance far above chance. Among the visual attributes that can
be discriminated with ambient vision are contrast, color,
orientation, and spatial frequency. Attention quantitatively
improves ambient vision in that it lowers various visual thresholds
by 20% to 70%. These changes are consistent with a computational
model, in which attention activates a winner-take-all competition
among visual filters. In addition, attention permits qualitatively
new kinds of discriminations that are not possible with ambient
vision. Among these are the discrimination of precise spatial
relationships and feature conjunctions. We propose that the various
perceptual consequences of attention reflect attentional
modulations at different levels of visual cortex.
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