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  Phase noise and the classification of natural images

Wichmann, F., Braun, D., & Gegenfurtner, K. (2006). Phase noise and the classification of natural images. Vision Research, 46(8-9), 1520-1529. doi:10.1016/j.visres.2005.11.008.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0013-D22B-9 Version Permalink: http://hdl.handle.net/21.11116/0000-0004-8685-E
Genre: Journal Article

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 Creators:
Wichmann, FA1, 2, Author              
Braun, DI, Author
Gegenfurtner, KR, Author              
Affiliations:
1Department Empirical Inference, Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497795              
2Max Planck Institute for Biological Cybernetics, Max Planck Society, Spemannstrasse 38, 72076 Tübingen, DE, ou_1497794              

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 Abstract: We measured the effect of global phase manipulations on a rapid animal categorization task. The Fourier spectra of our images of natural scenes were manipulated by adding zero-mean random phase noise at all spatial frequencies. The phase noise was the independent variable, uniformly and symmetrically distributed between 0 degree and ±180 degrees. Subjects were remarkably resistant to phase noise. Even with ±120 degree phase noise subjects were still performing at 75 correct. The high resistance of the subjects’ animal categorization rate to phase noise suggests that the visual system is highly robust to such random image changes. The proportion of correct answers closely followed the correlation between original and the phase noise-distorted images. Animal detection rate was higher when the same task was performed with contrast reduced versions of the same natural images, at contrasts where the contrast reduction mimicked that resulting from our phase randomization. Since the subjects’ categorization rate was better in the contrast experiment, reduction of local contrast alone cannot explain the performance in the phase noise experiment. This result obtained with natural images differs from those obtained for simple sinusoidal stimuli were performance changes due to phase changes are attributed to local contrast changes only. Thus the global phasechange accompanying disruption of image structure such as edges and object boundaries at different spatial scales reduces object classification over and above the performance deficit resulting from reducing contrast. Additional colour information improves the categorization performance by 2 .

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 Dates: 2006-04
 Publication Status: Published in print
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 Table of Contents: -
 Rev. Type: -
 Identifiers: DOI: 10.1016/j.visres.2005.11.008
BibTex Citekey: 3551
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Title: Vision Research
  Other : Vision Res.
Source Genre: Journal
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Publ. Info: Amsterdam : Pergamon
Pages: - Volume / Issue: 46 (8-9) Sequence Number: - Start / End Page: 1520 - 1529 Identifier: ISSN: 0042-6989
CoNE: https://pure.mpg.de/cone/journals/resource/954925451842