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When we expect important stimuli at a particular spatial location, how does our perceptual sensitivity change over space? Subjects were cued to expect a target stimulus at one location and then required to perform one of the following tasks at that and three other locations: luminance detection, brightness discrimination, orientation discrimination, or form(More)
We argue that some aspects of human spatial vision, particularly for textured patterns and scenes, can be described in terms of demodulation and predictive coding. Such nonlinear processes encode a pattern into local phasors that represent it completely as a modulation, in phase and amplitude, of a prediction associated with the image structure in some(More)
The mechanism by which visual-spatial attention affects the detection of faint signals has been the subject of considerable debate. It is well known that spatial cuing speeds signal detection. This may imply that attentional cuing modulates the processing of sensory information during detection or, alternatively, that cuing acts to create decision bias(More)
We investigated the randomness and uniqueness of human iris patterns by mathematically comparing 2.3 million different pairs of eye images. The phase structure of each iris pattern was extracted by demodulation with quadrature wavelets spanning several scales of analysis. The resulting distribution of phase sequence variation among different eyes was(More)
We investigate three schemes for severe compression of iris images, in order to assess what their impact would be on recognition performance of the algorithms deployed today for identifying persons by this biometric feature. Currently, standard iris images are 600 times larger than the IrisCode templates computed from them for database storage and search;(More)
The recently published paper by Rankin et al. [1] ''Iris recognition failure over time: The effects of texture'' is paradoxical because in fact no changes over time were demonstrated, either in the iris patterns or in the system performance. The authors measured iris recognition performance using ''local and non-local dipole and tripole'' methods of iris(More)
The authors generated 316,250 entire distributions of IrisCode impostor scores, each distribution obtained by comparing one iris against hundreds of thousands of others in a database including persons spanning 152 nationalities. Altogether 100 billion iris comparisons were performed in this study. The purpose was to evaluate whether, in the tradition of(More)
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