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Title:The Role of a "Limited Retinal Search Region" in the Perception of a Visually Stable World
Author(s):Currie, Christopher Byron
Doctoral Committee Chair(s):George McConkie
Department / Program:Psychology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Psychology, Experimental
Abstract:The proximal stimulus shifts position on our retinae with each saccade, but we perceive our world as stable and continuous, a phenomenon known as visual stability. An intra-saccadic stimulus shift paradigm was used to study this phenomenon. Most theories of visual stability implicitly assume the existence of a mechanism that spatially adjusts perceived locations associated with the retinal array by using, as a parameter, "extra-retinal eye position information" (EEPI), a signal that encodes the size and direction of the saccade. With regard to the detection of intra-saccadic stimulus shifts, this theory predicts that when the size of the intra-saccadic stimulus shift is large enough to overcome the level of noise in the extra-retinal signal (which is a function of the saccade length), the perceptual system will perceive the stimulus to be in a new location after the saccade. Thus, the prediction is that everything else being equal, the size of the saccade will determine the likelihood of detecting a stimulus shift. The results from the experiment reported in this paper challenge this idea. Participants were shown pictures that varied in terms of visual complexity. During a saccade to a pre-determined target object, the entire scene shifted 1.5°. Controlling for saccade length, picture shifts during saccades to large target object were detected less frequently than the same shifts during saccades to small target objects. Moreover, the direction of displacement relative to the saccade also affected detectability. Current extra-retinal based models of visual stability do not predict these results. However, the overall pattern of results is consistent with a new theory of visual stability, the Saccade Target Theory (McConkie & Currie, 1996). Finally, the pattern of results is consistent across scenes that varied in terms of visual complexity. Thus, the Saccade Target Theory is able to account for the detection of intra-saccadic stimulus shifts when the stimulus is both visually simple and visually complex.
Issue Date:2000
Description:104 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2000.
Other Identifier(s):(MiAaPQ)AAI9955602
Date Available in IDEALS:2015-09-25
Date Deposited:2000

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