Boucart M, Delord S, Giersch A, 1994, "The computation of contour information in complex objects" Perception 23(4) 399 – 409
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The computation of contour information in complex objects
Muriel Boucart, Sandrine Delord, Anne Giersch
Received 28 June 1993, in revised form 19 September 1993
Abstract. Perceptual organisation, and especially the computation of contour information, has been the object of considerable interest in the last few years. In the first part of the paper we review recent accounts on the mechanisms involved in the processing of contour. In. the second part we report an experiment designed to examine (1) how physical parameters such as spatial proximity and collinearity of elements affect the integration of global contour in objects and (2) whether the activation of stored representations of object facilitates the computation of contour. Incomplete forms varying in she spacing and the alignment of line segments on their contour were used as stimuli in a matching task. Subjects were asked to decide which of two laterally displayed figures matched a reference form presented previously. The matching target and the distract or were physically identical but differed in their orientation. In one condition the reference object was always an outline drawing of an object. In a second condition the reference object was either a complete object or a more or less identifiable incomplete form. Little variation in performance was found for forms having continous and discontinous contour up to a spacing of 5 pixels (10.8 min) between elements. Response times and errors increased abruptly beyond this limit. This effect occurred in the two conditions of reference stimulus, suggesting that the computation of contour information is more affected by physical constraints at early processes than by high-level processes involving activation of stored structural representations of objects.
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