By Don Kang and Oliver Housman COSMOS 2005 Eye image from: leftmenu.htm Brain Image from: poor concentration.htm How the eye and brain really interact

Eye-Brain Connection Both eyes are needed to have depth perception A problem with a child’s eye must be corrected before the age of six If not, the weak eye will stop sending messages to the brain

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Muller-Lyer Illusion

Possible Explanations The corner theory –the lines with fins can be compared to building corners –there is a finite distance between the two corners, making the exterior corner always appear larger –subconscious The area theory –People try to match areas instead of the length of lines –subconscious

Results of the Change in Fin Angle Hypothesis: the smaller the fin angle, the stronger the illusion Possible explanations -Corner theory: the closer to a corner, the sharper the angle; the farther away the corner, the more similar the lengths of lines -Area theory: the smaller the angle, the more dissimilar the areas 45° 60°75°

Results of the Change in Fin Length Hypothesis: 20 units will give the weakest illusion, 100 units stronger, and 65 units the strongest Possible explanations -Corner theory: the longer the fin length, the more the lines look like a building corner -Area theory: the shorter the fin length, the more similar the areas

Results of the Change in Shape Hypothesis: circles will give the weakest illusion, ellipses stronger, and the fins the strongest Possible explanation -Area theory: the difference of the areas of the two lines for each set is the same, so the strength of the illusion should be the same for each shape

Conclusion for Muller-Lyer Illusion The theories used to explain the illusion are incomplete because they did not support all the result The area theory, however, is a more thorough explanation because is can be used for all the variables Not enough people were tested to give sufficient data

The Poggendorf illusion is physical, in that it involves the interaction of angle sensitive cells in the eye and the brain The Muller-Lyer illusion is psychological, because it incorporates one’s past, cognitive knowledge

Sally Robinson Kathy Cooksey Gene Switkes Hillary O’Bryan Jason Porter Test Subjects John MartinCfAO