Discovery and representation of human strategies for visual search

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Title: Discovery and representation of human strategies for visual search
Author: Tavassoli, Abtine, 1978-
Abstract: Visual search can simply be defined as the task of looking for an object of interest in a visual environment . Due to its foveated nature , the human visual system succeeds at such task by making many discrete fixations linked by rapid eye movements called saccades . However , very little is known about how saccadic targets (fixation loci ) are selected by the brain in such naturalistic tasks . Discoveries to be made are not only invaluable to the field of vision science but are very important in designing automated vision systems , which to this day lag in performance vis -vis human observers . What I have sought to accomplish in this dissertation has been to reveal previously unknown saccadic targeting and target selection strategies used by human observers in naturalistic visual search tasks . My driving goal has been to understand how the brain selects fixation loci and target candidates upon fixation , with the objective of using these findings for automated fixation selection algorithms employed for visual search . I have proposed a novel and efficient technique akin to psychophysical reverse correlation to study human observer strategies in locating low -contrast targets under a variety of experimental conditions . My technique has successfully been used to study saccadic programming and target selection in various experimental conditions , including visual searches for targets with known characteristics , targets whose orientation attributes are not known a priori , and targets containing multiple orientations . I have found visual guidance in saccadic targeting and target selection under all experimental conditions , revealed by observers' selectivity for spatial frequencies and /or orientations of stimuli close to that of the target . I have shown that under uncertainty , observers rely on known target characteristics to direct their saccades and to select target candidates upon foveal scrutiny . Moreover , I have demonstrated that multiple orientation characteristics of targets are represented in observer search strategies , modulated by their sensitivity / selectivity for each orientation . Some of my findings have been applied towards applications for automated visual search algorithms .
URI: http : / /hdl .handle .net /2152 /3702
Date: 2008-08-29


Discovery and representation of human strategies for visual search. Doctoral dissertation, The University of Texas at Austin. Available electronically from http : / /hdl .handle .net /2152 /3702 .

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