Contrasting perspective and texture gradient cues in the Mueller-Lyer illusion : Judgement theories versus perspective theories


Bielski, Ronald.




Several attempts have been made to propose theories which would specify the perceptual mechanism responsible for the Mueller-Lyer illusion; however, few of the many experiments conducted using this illusion have made cross-theoretical comparisons. The purpose of the current investigation was to contrast predictions made by judgment and perspective theories, using stimuli which contained both perspective and texture gradient distance cues. The experiment employed  124 subjects who provided 22,320 points of subjective equality as measures of illusory distortion through the method of constant stimuli. The major results indicate that ohly the main effect of the perspective cue could be strongly associated with  illusion magnitude. This finding in itself does not differentiate judgment and perspective theories. However, the second strongest effect, the perspective by texture gradient cue interaction, was shown to clearly differentiate the prediction efficacies in that judgment theories provide a more complete and consistent explanation of the distortion found in the Mueller-Lyer illusion. The basic findings and data trends reported by Haesen (1974) were also observed. Finally, line proximity was suggested as a new variable by which judgment theories may be compared and which may provide a means of extending assimilation theory. 


Visual Perception
Optical Illusions




Carleton University

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Theses and Dissertations

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