Date on Master's Thesis/Doctoral Dissertation

5-1951

Document Type

Master's Thesis

Degree Name

M.A.

Department

Psychological and Brain Sciences

Committee Chair

Ammons, R. B.

Subject

Vision; Optical illusions

Abstract

Many conflicting reports have been given in the literature concerning the effect of various factors on the rate of reversal of figure and ground in reversible perspective. Flugel (7, 8) suggested that changes in eye movement increased the number of reversals. He thought that fixation on one part of the figure could lead to S’s interpretation of this part as being "nearer” the observer and that changes in perspective were induced by changing the fixation point. Donahue (5) found that there was a rhythm in the reversals but the shift in the fixation point was not in rhythm with the reversal. He suggested that "…the shifting appearance is due to central factors and that the eye movements depend upon the shifting appearance rather than vice versa…" (5, p. 616). The contention that eye movement caused the figures to fluctuate met a more vigorous blast from a later study. Higginson (13, p. 311), commented that "…the theory of eye-movements as constituting a determining factor…has not one single fact to serve as a scientific foundation." One investigator attempting to find an explanation for the phenomena of reversible Figure (5) doubted that a person's rate of reversals remained stable from one day to the next. Guilford and Braly's study (11) attacked this question of reliability. They found that the rate of reversal was fairly constant for the same individual from day to day. The reversals were especially consistent for the same individual throughout an hour of observation. The range of fluctuation rates among the various subjects was found to be quite high. Guilford and Braly inferred from this that the rate of fluctuation was a valid measure of some individual trait that is relatively constant. However, they could not find anything to which the rate of reversal was related. Additional attempts have made to ferret out factors to which the rate of reversal are related. Many investigators have studied the relationship between the rate of reversals and biological functionings. Two investigators (23, 3) found a relation between the rate of reversal and the fluctuation found in vaso-motor changes. McDougall (19) performed an experiment in which he produced fatigue in his subjects. Fatigue appeared to lengthen the time between reversals. It was inferred from this that fatigue raises the resistance in the nervous paths and this results in slow reversals. McDougall (18) elaborated on his theory that raising the resistance in the nervous paths resulted in slow reversals. He contended that traits of personality are related to the speed of the nervous impulses in the nervous system. On the basis of this assumption an attempt was made to discriminate between an "introverted" and an "extroverted" personality by administering reversible figure tests. Other research workers (16, 12, 11, 1, 21) have found 'supporting and conflicting evidence that "organic” and "functional" cases may be discriminated from "normals" in terms of their performance on reversing figures. Hunt states (16, p. 992) that “…although these few studies give no systematic picture of the receptive process in either ‘functional' ‘psychoses’ or the various ‘organic' conditions it appears tentatively that the perceptual processes show greater evidence of a deficit. Furthermore, the deficit appears to reside in the central processes initiated by receptor action, particularly in the response to patterns and the alteration of sets or attitudes. Some psychologists have proceeded to investigate factors determining the rate of fluctuation by exploring the effect of existing conditions during testing. Gordon (10) believed that the rate of reversal might be affected by the nature of the task or stimuli. She administered different figures of varying complexity and found that a book figure changed more rapidly than the Schroder stairs figure. She inferred from this that complexity of the figure tends to make the rate of fluctuation slower. Donahue (5) also conducted an experiment to find out if there was a difference in the fluctuation rate that might be attributed to complexity of the stimuli. His results in this respect were inconclusive, but he expressed the opinion that familiarity increased the rate of fluctuation. The hypothesis that familiarity nor previous knowledge of the figure influences the rate of reversal has been supported by findings in other studies (17, 24). Washburn (24, p. 638) states that her “results strongly suggest that the ease or difficulty of so-called voluntary control of the perceptual interpretations of these figures rests on two principles: (1) the simplicity or complexity of the response suggested, and (2) its frequency in ordinary life." The implication of the previously mentioned studies that fluctuational rate might increase with practice is supported by several experiments (4, 5, 14, 17). Kohler’s results (17) agreed with the findings of the other experiments cited, but he offered a physiological explanation of the results. He told two subjects to "keep" whatever figure they saw. They were given the task of observing a reversible figure (Rubin Disk) until it fluctuated five times. Although the subjects were told to hold the figure it fluctuated more rapidly as the length of time of observation increased. The subjects were given one minute rest between trials so that the reversals would not become less "orderly" with prolonged observations. Kohler (17, p. 72) inferred from this that “…a figure process seems to have some effect by which it tends to more and more block its own way.” He proposes from this that the phenomena of rate of reversal may be associated with changes in electrical currents in the nervous system. Other investigators (7, 4, 15, 17) proposed that a "set" or an “attitude" might produce differences in the rate of fluctuations. Bruner, Postman and Mosteller (4) told 1/3 of his subjects to hold the figure, as Kohler had. They also told 1/3 of the S’s to reverse the figure fast and the other 1/3 to try to let it reverse "naturally.” The individuals that were told to alternate the figure, reversed the figure much faster than those who were told to “hold" the figure. The investigator also found that interaction between subjects and set resulted in a wide range of differences.

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