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Modeling eye movements in visual agnosia with a saliency map approach: Bottom-up guidance or top-down strategy?

Foulsham, T and Barton, JJS and Kingstone, A and Dewhurst, R and Underwood, G (2011) 'Modeling eye movements in visual agnosia with a saliency map approach: Bottom-up guidance or top-down strategy?' Neural Networks, 24 (6). 665 - 677. ISSN 0893-6080

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Abstract

Two recent papers (Foulsham, Barton, Kingstone, Dewhurst, & Underwood, 2009; Mannan, Kennard, & Husain, 2009) report that neuropsychological patients with a profound object recognition problem (visual agnosic subjects) show differences from healthy observers in the way their eye movements are controlled when looking at images. The interpretation of these papers is that eye movements can be modeled as the selection of points on a saliency map, and that agnosic subjects show an increased reliance on visual saliency, i.e., brightness and contrast in low-level stimulus features. Here we review this approach and present new data from our own experiments with an agnosic patient that quantifies the relationship between saliency and fixation location. In addition, we consider whether the perceptual difficulties of individual patients might be modeled by selectively weighting the different features involved in a saliency map. Our data indicate that saliency is not always a good predictor of fixation in agnosia: even for our agnosic subject, as for normal observers, the saliency-fixation relationship varied as a function of the task. This means that top-down processes still have a significant effect on the earliest stages of scanning in the setting of visual agnosia, indicating severe limitations for the saliency map model. Top-down, active strategies-which are the hallmark of our human visual system-play a vital role in eye movement control, whether we know what we are looking at or not. © 2011 Elsevier Ltd.

Item Type: Article
Subjects: B Philosophy. Psychology. Religion > BF Psychology
Divisions: Faculty of Science and Health > Psychology, Department of
Depositing User: Jim Jamieson
Date Deposited: 14 Nov 2011 12:08
Last Modified: 05 Feb 2019 15:15
URI: http://repository.essex.ac.uk/id/eprint/1491

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