May 2008
Volume 8, Issue 6
Vision Sciences Society Annual Meeting Abstract  |   May 2008
Sensitivity to spatial distortion in natural scenes
Author Affiliations
  • Peter Bex
    Schepens Eye Research Institute, Harvard Medical School
Journal of Vision May 2008, Vol.8, 688. doi:
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      Peter Bex; Sensitivity to spatial distortion in natural scenes. Journal of Vision 2008;8(6):688.

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      © ARVO (1962-2015); The Authors (2016-present)

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Objective: The visual field generally appears veridical and undistorted in spite of variations in retinal projection and our poor sensitivity to spatial form in crowded peripheral vision. Here I measure sensitivity to spatial distortion to examine the accuracy of visual representation. Methods: Spatial distortions were generated within one quadrant of large natural scenes, pink noise or phase-randomized natural scenes. The transition from undistorted to distorted regions was smoothed with a Gaussian window. The period of distortion was varied between 0.25–16 c/deg using band-pass filtered noise, newly generated each trial, to control the spatial displacement of remapped pixels. The magnitude of distortion was under the control of a staircase to generate distortion Modulation Transfer Functions (dMTFs). The observer was required to indicate which quadrant contained the distortion in a 4AFC task with feedback. Results: Sensitivity to spatial distortion decreased with eccentricity (measured out to 8 deg) and required deformations as high as 2 deg. For natural scenes, dMTFs were band-pass with a peak for distortions over 1 c/deg. Sensitivity to distortions within pink noise or phase-randomized natural scenes was much higher and dMTFs for these stimuli were low-pass. Conclusions: The fact that sensitivity is higher for random phase images suggests surprisingly that the presence of edges and contours in real scenes masks the presence of distortions. The 1 c/deg peak in dMTFs suggests that contour-finding processes prefer orientation changes within around 1 deg. Overall, humans are extremely insensitive to spatial distortions in natural scenes, suggesting that, like the perception of blur, the appearance of veridical visual space is entirely an illusion.

Bex, P. (2008). Sensitivity to spatial distortion in natural scenes [Abstract]. Journal of Vision, 8(6):688, 688a,, doi:10.1167/8.6.688. [CrossRef]
 The Wellcome Trust.

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