Muller-Lyer Illusion, discovered in 1888, is very famous. This experiment presents variations including the tails-out with no line, tails-out middle dot and tails-out three dots. Eight different configurations were shown on the computer screen in pairs. the magnitude of the illusion for each configuration was then compared to the original illusion to see which will have the greatest illusion?
Figure 1. Four different experiments in eight configurations, such as dot to dot whiout line, control line, tails-out without line, tails-out with dot in the middle, and tails-out with several dots in the middle.
Methods
The subjects were 17 undergraduate students, 10 females and 7 males. The students were recruited randomly from the Alma College campus.
Design. Using the method of comparison and adjustment, each subject measured eight different configurations of the Muller-Lyer illusion. Since these configurations were grouped in pairs, 4 groups were presented three times each. Muller-Lyer illusion dot to dot without line compared to control line; Muller-Lyer illusion tails-out compared to tails-out without line; Muller-Lyer illusion tails-out with dot in the middle compared to just tails-out; tails-out with several dots in the middle compared to just tails-out.
Materials. The configurations were presented on the computer using the Eye Lines software. The image was black on the white background. The image was positioned in front of the subject's eyes in the middle of the Macintosh computer screen.
Procedure. The experiment was done in the Psychoilogy Lab room. Each subject sat in front of the computer screen and made adjustments for 12 trials (4 groups presented 3 times each). These 12 trials were presented in random order.
Results
Figure 2 shows that the Muller-Lyer illusion in the altered configurations have a weaker magnitude than the original illusion. The comparison of the control line and dot to dot without line orientation shows the greatest amount of illusion of all orientations. In Trial 1, where the control line was compared to dot to dot without line orientation, the average amount of illusion for the subjects was 162.078 units. For Trial 2, where the tails-out without line configuration was compare to the regular tails-out orientation, the average amount of illusion 92.059 units. Trial 3, the group that compared tails-out with several dots to just tails-out, had an average of 22.176 units. Trial 4, where the tails-out with dot in middle was compared to just tails-out, had an average of 45.471 for the amount of illusion.
Figure 2. The results of Muller-Lyer illusion in eight different configurations, shown as four groups.
Discussion
This experiment shows that the different configurations make a difference in Muller-Lyer illusion. Configurations with without the horizontal line produce less illusion. This illusion is greater because the control line is much harder to adjust. The control line was adjusted with dots, with no line in between, and because of this it is difficult to visualize the invisible line. The other configurations demonstrated less illusion because it was easier to see the distance and it's methos of adjustment was measured against the original tailsout experiment. Trials 2, 3, and 4 were similar to the original experiment. The experiments were the line, several dots and middle dot orientations, which did not made a great impact, but instead of it created significantly less illusion. In previous studies with dot orientations of the illusion, the effect was significant only for the tails-out with several dots. This study, however, did not show that effect. More speculatively, the eyes could be trained, get use to the screen and it's conditions. Finally, it is unclear why the control line illusion in trial 1 caused a greater and stronger effect on Muller-Lyer illusion than any other orientations. The mean of the control is significantly higher. It is possible that trials 2, 3, and 4 are very similar and less effective because they have less distortion.
References
Beagley, W. (1985). Interaction of Muller-Lyer with filled-unfilled space illusion: An explanation of Muller-Lyer asymmetry. Perception and Psychophysics, 37, 45-49
Di Maio, V., & Lansky, P. (1998). The Muller-Lyer Illusion In Interpolated Figures. perceptual & Motor Skills, 87, 499-504.
Nelson, B., & Greene, E. (1998). Similar Muller-Lyer Effects From Operant And Comparison Response Modes. Perceptual & Motor Skills, 86, 499-511.
Sekuler, R., & Erlebacher, A. (1971). The two illusions of Muller- Lyer: Confusion theory reexamined. American Journal of Psychology, 84, 477-486.
Anii, A., & Kudo, K. (1997). Effects of instruction and practice on the length-reproduction task using the Muller-Lyer figure. Perceptual & Motor Skills, 85, 819-825.
Gillam, B., & Chambers, D. (1985). Size and position are incongruos: Measurements on the Muller-Lyer figure. Perception & Psychophysics, 37, 549-556.
Meyer, G. E. (1986). Interactions of subjectivve contours with the Ponzo, Muller-Lyer, and vertical-horizontal illusions. Bulletin of the Psychonomic Society, 24, 39-40.
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