September 2011
Volume 11, Issue 11
Vision Sciences Society Annual Meeting Abstract  |   September 2011
The effect of viewing eccentricity on visual enumeration
Author Affiliations
  • Breana Carter
    Department of Psychology, University of South Carolina
  • Paul Smith
    Department of Psychology, University of South Carolina
  • Melanie Palomares
    Department of Psychology, University of South Carolina
Journal of Vision September 2011, Vol.11, 1208. doi:
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      Breana Carter, Paul Smith, Melanie Palomares; The effect of viewing eccentricity on visual enumeration. Journal of Vision 2011;11(11):1208.

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

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Visual acuity and contrast sensitivity progressively diminish with increasing viewing eccentricity. Here we evaluated how visual enumeration is affected by visual eccentricity, and whether subitizing capacity, the accurate enumeration of a small number (<3–4) of items, decreases with more eccentric viewing. Participants enumerated gratings (0–9) presented for 50 ms along an imaginary circle at eccentricities of 2.25, 4.5, 6.75, 9 and 11.25 deg. We found that enumeration accuracies (proportion correct) decreased with increasing eccentricity. However, the subitzing capacity was constant at 3 items across all eccentricities except at 11.25 deg, where subitizing capacity was decreased to 2 items. We also analyzed the distribution of the responses. Mean responses as a function of number deviated from the unit slope as the gratings were presented at larger eccentricities. The coefficient of variation, a normalized metric of enumeration precision defined as the standard deviation divided by the mean (Palomares & Egeth, 2010), plotted against number of patches resulted in log-log slopes ranging from −.39 to −.65. Our results show that increasing viewing eccentricity makes enumeration less accurate, but that the critical features of enumeration functions are generally resistant to the effects of viewing eccentricity.

Undergraduate Explorers Research Award. 

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