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Characteristics of the central performance drop


Characteristics of the central performance drop

Potechin, Cindy J (2006) Characteristics of the central performance drop. PhD thesis, Concordia University.

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The present experiments examine texture discrimination as a function of eccentricity. Before 1985, several studies showed that sensitivity to texture differences decreased with eccentricity. Kehrer (1987) found that the detection of a small patch of oblique lines oriented at ±45 deg from vertical embedded in a background of orthogonal lines improved as the texture was moved away from the fovea. Kehrer (1989) attributed this so called "Central Performance Drop" (CPD) to a difference in processing speed of spatial-frequency selective filters across the visual field. Gurnsey et al. (1996) proposed a spatial account for the CPD, asserting that the CPD represents a mismatch between the texture scale and the spatial frequency selectivity of the texture detection mechanism. It has been argued that a backward mask is critical to the emergence of a CPD. We show that the CPD can be elicited without a backward mask when performance is limited by manipulating the orientation variability within the foreground and background textures. (Potechin & Gurnsey, 2003). Texture discrimination is often asymmetrical; i.e. Texture A embedded in Texture B may be easier to detect than vice versa. We examined texture discrimination as a function of eccentricity using four textures that were previously reported to elicit discrimination asymmetries. Three different patterns emerged in which the discrimination asymmetries were not necessarily constant across eccentricity and not all textures elicited a CPD. The results show that "discriminability" of two textures depends upon the eccentricity of the target texture and on the arrangement of the two textures within the display (Potechin & Gurnsey, in press). Both the spatial and temporal explanations for the CPD assume that lower spatial frequencies are not as efficiently processed in the fovea compared to higher spatial frequencies. It has been suggested that cross-frequency inhibition (CFI) or the preference given to high spatial frequency information at the fovea may underlie the CPD. We observed that high frequency attenuation of a stimulus by a Gaussian filter can improve discrimination performance at the fovea, suggesting that the CPD may be influenced by CFI

Divisions:Concordia University > Faculty of Arts and Science > Psychology
Item Type:Thesis (PhD)
Authors:Potechin, Cindy J
Pagination:xiii, 141 leaves. : ill. ; 29 cm.
Institution:Concordia University
Degree Name:Ph. D.
Thesis Supervisor(s):Gurnsey, Rick
Identification Number:LE 3 C66P79P 2006 P68
ID Code:9185
Deposited By: Concordia University Library
Deposited On:18 Aug 2011 18:46
Last Modified:13 Jul 2020 20:06
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