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Proceedings Paper

Modeling cognitive effects on visual search for targets in cluttered backgrounds
Author(s): Magnus Snorrason; Harald Ruda; James Hoffman
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Paper Abstract

To understand how a human operator performs visual search in complex scenes, it is necessary to take into account top- down cognitive biases in addition to bottom-up visual saliency effects. We constructed a model to elucidate the relationship between saliency and cognitive effects in the domain of visual search for distant targets in photo- realistic images of cluttered scenes. In this domain, detecting targets is difficult and requires high visual acuity. Sufficient acuity is only available near the fixation point, i.e. in the fovea. Hence, the choice of fixation points is the most important determinant of whether targets get detected. We developed a model that predicts the 2D distribution of fixation probabilities directly from an image. Fixation probabilities were computed as a function of local contrast (saliency effect) and proximity to the horizon (cognitive effect: distant targets are more likely to be found c close to the horizon). For validation, the model's predictions were compared to ensemble statistics of subjects' actual fixation locations, collected with an eye- tracker. The model's predictions correlated well with the observed data. Disabling the horizon-proximity functionality of the model significantly degraded prediction accuracy, demonstrating that cognitive effects must be accounted for when modeling visual search.

Paper Details

Date Published: 7 July 1998
PDF: 12 pages
Proc. SPIE 3375, Targets and Backgrounds: Characterization and Representation IV, (7 July 1998); doi: 10.1117/12.327144
Show Author Affiliations
Magnus Snorrason, Charles River Analytics (United States)
Harald Ruda, Charles River Analytics (United States)
James Hoffman, Univ. of Delaware (United States)

Published in SPIE Proceedings Vol. 3375:
Targets and Backgrounds: Characterization and Representation IV
Wendell R. Watkins; Dieter Clement, Editor(s)

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