The effects of task difficulty on visual search strategy in virtual 3D displays

Analyzing the factors that determine our choice of visual search strategy may shed light on visual behavior in everyday situations. Previous results suggest that increasing task difficulty leads to more systematic search paths. Here we analyze observers' eye movements in an ''easy'' conjunction search task and a ''difficult'' shape search task to study visual search strategies in stereoscopic search displays with virtual depth induced by binocular disparity. Standard eye-movement variables, such as fixation duration and initial saccade latency, as well as new measures proposed here, such as saccadic step size, relative saccadic selectivity, and xÀy target distance, revealed systematic effects on search dynamics in the horizontal-vertical plane throughout the search process. We found that in the ''easy'' task, observers start with the processing of display items in the display center immediately after stimulus onset and subsequently move their gaze outwards, guided by extrafoveally perceived stimulus color. In contrast, the ''difficult'' task induced an initial gaze shift to the upperleft display corner, followed by a systematic left-right and top-down search process. The only consistent depth effect was a trend of initial saccades in the easy task with smallest displays to the items closest to the observer. The results demonstrate the utility of eyemovement analysis for understanding search strategies and provide a first step toward studying search strategies in actual 3D scenarios

Elementary Motion Analysis Using a Retina-Inspired Neural Network

The processing that occurs in an animal’s retina is much more complex than once believed. In addition to highlighting highcontrast areas, the retina also performs a simple motion analysis of the visual field. Moreover, a full understanding of the neural functioning that occurs within the retina is not likely to take place anytime soon. Nevertheless, our present knowledge of the organization of retinal neurons and their responses to stimulation is enough to model meaningful and effective visual processing systems after. In this paper, following a very general, high-level overview of retinal organization and functioning, we demonstrate a neural system that mimics the simple motion analysis that occurs within the retina. The neural system described is modeled after a subset of the connections that are present in most vertebrate retinas

Inspection time and visual–perceptual processing

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