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Wilson Geisler, Jeffrey Perry, Jiri Najemnik; Analysis of visual search using gaze contingent displays and ideal observers. Journal of Vision 2004;4(11):16. doi: https://doi.org/10.1167/4.11.16.
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© ARVO (1962-2015); The Authors (2016-present)
We have developed an algorithm and software for creating displays where either spatial resolution or chromatic content can be varied arbitrarily across the visual field, contingent on the current gaze direction (see http://svi.cps.utexas.edu/). We have been using this software to analyze the mechanisms of visual search. Search time and eye movements were measured while subjects searched for Gabor targets in 1/f noise. We varied, parametrically, target spatial frequency, noise contrast, and rate of fall-off in display resolution from the point of fixation. This experiment provides quantitative data on how information in the periphery contributes to search performance and to the pattern of eye movements. We find that the shape of the function describing search time (and number of fixations) versus degree of foveation is dependent upon target spatial frequency, but is independent of noise contrast. Interestingly, we find that human search performance in this complex task approaches that of an ideal observer (with the same spatial resolution as the human visual system), even though humans have very limited visual memory, and presumably cannot integrate information optimally across many fixations. Analysis of the ideal observer shows that, in fact, there is little benefit either from having detailed visual memories or from integrating information perfectly across fixations. Much more important is efficient parallel processing of the information on each fixation.
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