THE ASSESSMENT THROUGH BACKWARD MASKING OF COGNITIVE PROCESSING CHARACTERISTICS IN THE LEFT AND RIGHT VISUAL FIELDS.
Item
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Title
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THE ASSESSMENT THROUGH BACKWARD MASKING OF COGNITIVE PROCESSING CHARACTERISTICS IN THE LEFT AND RIGHT VISUAL FIELDS.
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Identifier
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AAI8112756
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identifier
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8112756
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Creator
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GREENBLATT, EDWARD ROBERT.
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Contributor
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Dr. Jeffrey Rosen
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Date
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1981
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Language
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English
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Publisher
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City University of New York.
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Subject
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Psychology, Experimental
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Abstract
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A central backward masking procedure was used to determine cognitive differences between the right visual field (RVF) and the left visual field (LVF). Briefly, this technique involves the successive presentation of two briefly exposed stimuli. The first is the target (T) configuration, in this case letters which the S must identify. The second stimulus is the mask (M) which is made up of straight lines. Both the T and M are lateralized to a VF and spatially encompasses the same location. This technique permits temporal pattern assessment in performance (the number of letters correctly identified) as a function of increasing time delays between the T and M for the LVF and RVF.;In experiment I, the RVF performance was significantly better than the LVF (p < .01). In addition, the 13 intervals used between the onset of the T and the onset of the M, called the stimulus onset Asynchrony (SOA), had a significant effect on the number of letter pairs that could be identified (p < .01). The SOA ranged from 0 to 120 msec in intervals of tens. Finally there was a marginal VF by SOA interaction (p < .067). The performance function for each VF contained significant linear, quadratic and cubic trend components. Maximum decrement in performance occurred sooner for LVF presented letters compared to the RVF presented letters. In addition, the decrement and improvement (or slope) in the quadratic component was found to be more gradual for the LVF. Thus vulnerability to the M encompassed a longer duration for LVF presented letters. These results suggest that the cognitive operations necessary in identifying letters are different for the two hemispheres. Although letter identification is superior for RVF presented letters, the initiation of a cognitive process commenced sooner for the LVF compared to the RVF.;Further assessment of processing differences between the hemispheres was thought possible by using a second M with a lower density level (or the ratio of darkened area encompassed by the lines, to the white background). If the processing characteristics were indeed different, then the second M should have a differential impact on the performance functions for the given hemisphere.;Results indicated that performance was significantly better for RVF presented letters, that SOA significantly affected performance and that there was a VF by SOA interaction, all replicating experiment I. In addition, the two masks had a differential affect on performance (p < .01). The three way interaction, M by VF by SOA, was also significant supporting the prediction that processing would be differentially affected by the change in M density.;Further analysis revealed that different trend components were significantly affected by the change in the M when the two VFs were compared. For both VFs the first half of the function was affected by the change in the M leaving the remaining half of the function primarily intact. Visual inspection suggests that the three way interaction was primarily the result of the change in the function for LVF presented letters. This was noted by a dramatic change in the period of vulnerability to the M. Decreasing the density decreased the vulnerability to the M as measured by performance.;Different models are discussed to account for the results in experiments I and II. They encompass issues related to interhemispheric transfer time as well as qualitative differences in processing for the separate hemispheres. Finally, further research is discussed in order to investigate these differences more thoroughly.;This includes increasing the number of letters in the array as well as using different stimuli.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Psychology
