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  Effects of parametric manipulation of inter-stimulus similarity on 3D object categorization

Edelman, S., Bülthoff, H., & Bülthoff, I. (1999). Effects of parametric manipulation of inter-stimulus similarity on 3D object categorization. Spatial Vision, 12(1), 107-123. doi:10.1163/156856899X00067.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0013-E70B-6 Version Permalink: http://hdl.handle.net/21.11116/0000-0006-47CE-3
Genre: Journal Article

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Edelman, S, Author              
Bülthoff, HH1, 2, Author              
Bülthoff, I1, 2, Author              
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1Department Human Perception, Cognition and Action, Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497797              
2Max Planck Institute for Biological Cybernetics, Max Planck Society, Spemannstrasse 38, 72076 Tübingen, DE, ou_1497794              

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 Abstract: To explore the nature of the representation space of 3D objects, we studied human performance in forced-choice categorization of objects composed of four geon-like parts emanating from a common center. Two categories were defined by prototypical objects, distinguished by qualitative properties of their parts (bulging vs waist-like limbs). Subjects were trained to discriminate between the two prototypes (shown briefly, from a number of viewpoints, in stereo) in a 1-interval forced-choice task, until they reached a 90 correct-response performance level. After training, in the first experiment, 11 subjects were tested on shapes obtained by varying the prototypical parameters both orthogonally (ORTHO) and in parallel (PARA) to the line connecting the prototypes in the parameter space. For the eight subjects who performed above chance, the error rate increased with the ORTHO parameter-space displacement between the stimulus and the corresponding prototype; the effect of the PARA displacement was weaker. Thus, the parameter-space location of the stimuli mattered more than the qualitative contrasts, which were always present. To find out whether both prototypes or just the nearest one to the test shape influenced the decision, in the second experiment we varied the similarity between the categories. Specifically, in the test stage trials the distance between the two prototypes could assume one of three values (FAR, INTERMEDIATE, and NEAR). For the 13 subjects who performed above chance, the error rate (on physically identical stimuli) in the NEAR condition was higher than in the other two conditions. The results of the two experiments contradict the prediction of theories that postulate exclusive reliance on qualitative contrasts, and support the notion of a representation space in which distances to more than one reference point or prototype are encoded (Edelman, 1998).

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 Dates: 1999-01
 Publication Status: Published in print
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 Identifiers: DOI: 10.1163/156856899X00067
BibTex Citekey: 184
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Title: Spatial Vision
  Other : Spatial Vis.
Source Genre: Journal
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Publ. Info: Utrecht, Netherlands : VNU Science Press
Pages: - Volume / Issue: 12 (1) Sequence Number: - Start / End Page: 107 - 123 Identifier: ISSN: 0169-1015
CoNE: https://pure.mpg.de/cone/journals/resource/954927621090