MONOCULAR RECOGNITION OF VERTICALLY-ORIENTED WORDS AND LANDOLT CS IN THE VISUAL HALF-FIELDS.
Item
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Title
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MONOCULAR RECOGNITION OF VERTICALLY-ORIENTED WORDS AND LANDOLT CS IN THE VISUAL HALF-FIELDS.
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Identifier
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AAI8119652
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identifier
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8119652
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Creator
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D'AMICO, THEODORE FORTUNATO.
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Contributor
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William S. Battersby
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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, Physiological
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Abstract
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All past tachistoscopic studies that have been conducted to investigate hemispheric asymmetries for the processing of alphabetical material can be criticized for using a verbal response indicator and/or failing to control simultaneously for directional reading habits and the influence of peripheral factors. In addition, many of these studies can be criticized for (a) their reliance on group data, (b) their failure to attend to differences in luminance in the two visual half-fields, and/or (c) their use of a single measure (e.g., percent correct recognition) to evaluate functional hemispheric differences.;In the present study, an attempt was made to correct for the shortcomings of these past studies. Towards that end, five dextral and three sinistral observes (Os) were tested monocularly in four test sessions. In each session, either vertically-mounted words or Landolt Cs were presented one at a time to either the left or right of fixation using a tachistoscope that illuminated the two visual half-fields equally. All stimuli were presented at a retinal eccentricity of 3(DEGREES) at one of three exposure durations. The exposure durations were selected at the beginning of each test session in an attempt to generate recognition rates ranging from approximately 10% to 80% correct so that estimates of threshold (50% correct) exposure duration could be calculated.;The task was a "go, no-go" RT discrimination: O was required to release a telegraph key as rapidly as possible following the presentation of certain (positive) stimuli and not to release the key following the presentation of other (negative) stimuli. Responses to negative stimuli provided the basis for determining whether the criterion level of responding was comparable for left and right visual field presentations; responses to positive stimuli, and the latencies of these responses, provided the basis for measuring half-field differences in percent correct recognition and reaction time, respectively. For each of these measures, as well as threshold exposure duration, half-field differences for the left and right eye viewing of words were evaluated on a group and individual basis in terms of their statistical significance after the data were adjusted for differences in hemiretinal acuity. These adjustments were accomplished by subtracting, for a given eye, RVF-LVF differences for the viewing of Landolt Cs from RVF-LVF differences for the viewing of words (acuity baseline comparisons).;In general, the results indicated that the two cerebral hemispheres differ in their ability to process tachistoscopically presented alphabetical material. As a group, dextral Os showed a significant RVF superiority for percent correct recognition and threshold exposure duration in both the left and right eye viewing conditions, and a significant RVF superiority for reaction time in the right eye viewing condition. In comparison, all half-field differences for the above three measures were not significant for the sinistral group.;Although in many cases the results failed to reach significance, the data for individual Os also indicated that the processing of alphabetical material is not performed equally well by the two hemispheres. For both left and right eye viewing, all five dextral Os showed a favoring of the RVF for percent correct recognition and threshold exposure duration, and four of the five dextral Os showed a favoring of the RVF for reaction time. In comparison, all half-field recognition, threshold and reaction time differences for two of the three sinistral Os were nonsignificant and small relative to the half-field differences that obtained for the average dextral O.;The results were discussed in terms of (a) Kimura's hemispheric specialization hypothesis, (b) the correspondence between recognition and reaction time measures for evaluating half-field differences, and (c) previous half-field studies that have used a monocular viewing paradigm.
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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
