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Visual Illusions:. How the eye and brain really interact. By Don Kang and Oliver Housman COSMOS 2005 Eye image from: www.hkvisioncare.com/ leftmenu.htm Brain Image from: www.turobread.com/ poor concentration.htm. Eye-Brain Connection. Both eyes are needed to have depth perception. - PowerPoint PPT Presentation
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By Don Kang and Oliver Housman
COSMOS 2005
Eye image from: www.hkvisioncare.com/ leftmenu.htm
Brain Image from: www.turobread.com/ poor concentration.htm
How the eye and brain really interact
Eye-Brain Connection
• Both eyes are needed to have depth perception
http://www.nei.nih.gov/nehep/summer03/
• 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
http://www.31alumni.com/photos/31-eyewitness-ratings-ad.gif
http://www.medem.com/MedLB/article_detaillb.cfm?article_ID=ZZZRWUDSIAC&sub_cat=189
http://www.chemistry.ucsc.edu/teaching/switkes/COSMOS/VISION/WWW_05/illusions/OLIVER/Poggendorf_Oliver.html
http://www.chemistry.ucsc.edu/teaching/switkes/COSMOS/VISION/WWW_05/illusions/OLIVER/Poggendorf_Oliver.html
Black Orange Cyan
Vertical Horizontal
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- -+
10°
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
http://www.pc.rhbnc.ac.uk/illusions/Image46.gif
• The area theory– People try to match areas
instead of the length of lines– subconscious
Results of the Change in Fin Angle
Ratio of Line Lengths with Differing Fin Angles
0.85
0.95
1.05
1.15
1.25
1.35
40 50 60 70 80
Degrees of Angles
Ratio
of Li
ne Le
ngths
• 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
Ratio of Line Lengths with Differing Fin Lengths
0.850.900.951.001.05
1.101.151.201.251.30
0 20 40 60 80 100 120
Fin Length
Line L
ength
• 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
20
65 100
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 Martin CfAO