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Exploring Human Sensitivity to Contrast in Blackshot Texture Segregation

Discover the unexpected depth of human perception in analyzing textures with the Blackshot model. Research uncovers a novel nonlinearity in contrast perception.

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Exploring Human Sensitivity to Contrast in Blackshot Texture Segregation

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  1. Blackshot: An Unexpected Dimension of Human Sensitivity to Contrast Michael S. Landy New York University Charles Chubb University of California, Irvine John Econopouly

  2. Outline • Back pocket model of texture segregation • Investigating a nonlinearity: IID textures • Filling in the missing information • Result: Blackshot

  3. Texture Segregation Luminance Edge Texture Edge

  4. The Back Pocket Model

  5. Application of the Back Pocket Model Input Vertically filtered Squared 2nd-Order filtered

  6. The Back Pocket Model

  7. How to Measure the Nonlinearity • Simple case: Independent, Identically Distributed (IID) textures • Appearance indicates at least two channels or nonlinearities: perceived brightness and contrast • Technique: Histogram Contrast Analysis (Chubb, Econopouly & Landy, 1994) • Result: a third perceptual dimension

  8. IID Textures: The Uniform Histogram

  9. IID Textures: 1st-Order Modulator = Brightness

  10. IID Textures: 2nd-Order Modulator = Contrast

  11. Histogram Modulators

  12. Nth-Order, Orthogonal Histogram Modulators 1 2 3 4 5 6 7 Response Contrast

  13. Histogram Contrast Thresholds

  14. The Result (Chubb et al., 1994): fCEL fCEL: 3rd- through 7th-order components

  15. The New Technique: Tradeoff of 1 or 2 with fCEL 1 fCELAmplitude 0 or or -1 0 1 1 or 2Amplitude

  16. Experimental Details • 3 Subjects • Carefully linearized lookup table • 200 ms display

  17. Task: 4-AFC Shape Discrimination

  18. Results: Three Thresholds  

  19. Results: Reconstructed Nonlinearity

  20. Conclusions • Full measurement of a novel nonlinearity • Blackshot: Exquisite sensitivity to the darkest texels • Thus, 3 dimensions of IID texture appearance: brightness, contrast and blackshot • A striking precedent: Whittle (1986)

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