Detecting a visual object in the presence of other objects : the flanker facilitation effect in contour integration

When an observer views a complex visual scene and tries to identify an object, his or her visual system must decide what regions of the visual field correspond to the object of interest and which do not. One aspect of this process involves the grouping of the local contrast information (e.g., orient...

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Main Author: Gillespie, Christopher
Other Authors: Vishwanath, Dhanraj ; Harris, Julie
Published: University of St Andrews 2015
Subjects:
Online Access:http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.694547
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spelling ndltd-bl.uk-oai-ethos.bl.uk-6945472018-04-04T03:28:02ZDetecting a visual object in the presence of other objects : the flanker facilitation effect in contour integrationGillespie, ChristopherVishwanath, Dhanraj ; Harris, Julie2015When an observer views a complex visual scene and tries to identify an object, his or her visual system must decide what regions of the visual field correspond to the object of interest and which do not. One aspect of this process involves the grouping of the local contrast information (e.g., orientation, position and frequency) into a smooth contour object. This thesis investigated whether the presence of other flanking objects affected this contour integration of a central target contour. To test this, a set of Gaborized contour shapes were embedded in a randomised Gabor noise field. The detectability of the contours was altered by adjusting the alignment of the Gabor patches in the contour (orientation jitter) until a participant was unable to distinguish between a field with and without a target shape (2-AFC procedure). By varying the magnitude of this jitter, detection thresholds were determined for target contours under various experimental conditions. These thresholds were used to investigate whether contour integration was sensitive to shared shape information between objects across the visual field. This thesis determined that the presence of flanking contours of a similar shape (as the target) facilitated the detection of a noisy target contour. The specific results suggest that this facilitation does not involve a simple template matching or shape priming but is associated with integration of shape level information in the detection of the most likely smooth closed contour. The magnitude of this flanker facilitation effect was sensitive to a number of factors (e.g., numerosity, relative position of the flankers, and perimeter complexity/compactness). The implication of these findings is that the processing of highly localised contrast and orientation information originating from a single object is subject to modulation from other sources of shape information across the whole of the visual field.152.14University of St Andrewshttp://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.694547http://hdl.handle.net/10023/9479Electronic Thesis or Dissertation
collection NDLTD
sources NDLTD
topic 152.14
spellingShingle 152.14
Gillespie, Christopher
Detecting a visual object in the presence of other objects : the flanker facilitation effect in contour integration
description When an observer views a complex visual scene and tries to identify an object, his or her visual system must decide what regions of the visual field correspond to the object of interest and which do not. One aspect of this process involves the grouping of the local contrast information (e.g., orientation, position and frequency) into a smooth contour object. This thesis investigated whether the presence of other flanking objects affected this contour integration of a central target contour. To test this, a set of Gaborized contour shapes were embedded in a randomised Gabor noise field. The detectability of the contours was altered by adjusting the alignment of the Gabor patches in the contour (orientation jitter) until a participant was unable to distinguish between a field with and without a target shape (2-AFC procedure). By varying the magnitude of this jitter, detection thresholds were determined for target contours under various experimental conditions. These thresholds were used to investigate whether contour integration was sensitive to shared shape information between objects across the visual field. This thesis determined that the presence of flanking contours of a similar shape (as the target) facilitated the detection of a noisy target contour. The specific results suggest that this facilitation does not involve a simple template matching or shape priming but is associated with integration of shape level information in the detection of the most likely smooth closed contour. The magnitude of this flanker facilitation effect was sensitive to a number of factors (e.g., numerosity, relative position of the flankers, and perimeter complexity/compactness). The implication of these findings is that the processing of highly localised contrast and orientation information originating from a single object is subject to modulation from other sources of shape information across the whole of the visual field.
author2 Vishwanath, Dhanraj ; Harris, Julie
author_facet Vishwanath, Dhanraj ; Harris, Julie
Gillespie, Christopher
author Gillespie, Christopher
author_sort Gillespie, Christopher
title Detecting a visual object in the presence of other objects : the flanker facilitation effect in contour integration
title_short Detecting a visual object in the presence of other objects : the flanker facilitation effect in contour integration
title_full Detecting a visual object in the presence of other objects : the flanker facilitation effect in contour integration
title_fullStr Detecting a visual object in the presence of other objects : the flanker facilitation effect in contour integration
title_full_unstemmed Detecting a visual object in the presence of other objects : the flanker facilitation effect in contour integration
title_sort detecting a visual object in the presence of other objects : the flanker facilitation effect in contour integration
publisher University of St Andrews
publishDate 2015
url http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.694547
work_keys_str_mv AT gillespiechristopher detectingavisualobjectinthepresenceofotherobjectstheflankerfacilitationeffectincontourintegration
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