August 2012
Volume 12, Issue 9
Free
Vision Sciences Society Annual Meeting Abstract  |   August 2012
Judgment of angular declination, but not of vertical angular size, is accurate
Author Affiliations
  • Ruohai Wang
    University of Louisville, USA
  • Brendan McHugh
    University of Louisville, USA
  • Teng Leng Ooi
    Pennsylvania College of Optometry at Salus University, USA
  • Zijiang He
    University of Louisville, USA
Journal of Vision August 2012, Vol.12, 906. doi:10.1167/12.9.906
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      Ruohai Wang, Brendan McHugh, Teng Leng Ooi, Zijiang He; Judgment of angular declination, but not of vertical angular size, is accurate. Journal of Vision 2012;12(9):906. doi: 10.1167/12.9.906.

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

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Abstract

Phenomenological visual space provides a basis for perceptual judgments of spatial relationships. The latter, in turn, allows us to reveal the intricacies of space perception. However, not all spatial judgments are reliable. One reason could be due to an inadequate gauging rather than to inaccurate sensory information. We compared the judgments of angular declination (direction) and angular size over a range of 8o-35o in a full cue environment. In Experiment 1, observers instructed the experimenter to adjust the height (angular declination) of a sphere (0.84o) placed at 1.5 m to match that of a test target (0.69o sphere) at 0.5 m. We found a linear matching function of angular declination specified by, y=0.9746x-2.0324, where y and x are, respectively, the matched and test angular declination (R2=0.997). Remarkably, the finding of a slope approaching unity is similar to the previous finding by Ooi et al (2001) who used a blind walking-gesturing task in the dark. They showed that while an observer’s walked distance and gestured height of a previously viewed dimly-lit target were inaccurate, the estimated angular declination was veridical. Experiment 2 measured angular size. Two vertically aligned test spheres (0.65o) were placed at 0.5 m. We found the matching functions are non-veridical and significantly affected by the distance and configuration of the matching targets. (i) The matching function of angular size is y=0.714x+4.784 (R2=0.998) when the two matching targets (0.84o spheres) were vertically aligned and placed at 1.5 m. (ii) The matching function is y=0.770x+1.037 (R2=1.000) when the two matching targets were vertically misaligned, wherein one was placed at 1.5 m (0.84o sphere) and the other at 5.63 m (0.39o sphere at the eye level). Altogether, our findings reveal that the visual system accurately gauges angular declination but not angular size.

Meeting abstract presented at VSS 2012

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