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By Don Kang and Oliver Housman COSMOS 2005 Eye image from: hkvisioncare/ leftmenu.htm

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.

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By Don Kang and Oliver Housman COSMOS 2005 Eye image from: hkvisioncare/ leftmenu.htm

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  1. 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

  2. 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 http://www.nei.nih.gov/nehep/summer03/

  3. Brain-Eye Injuries Another reason to study illusions is... Strokes Eyewitness Accounts http://www.31alumni.com/photos/31-eyewitness-ratings-ad.gif http://www.medem.com/MedLB/article_detaillb.cfm?article_ID=ZZZRWUDSIAC&sub_cat=189

  4. Poggendorf Illusion Line A Line B http://www.chemistry.ucsc.edu/teaching/switkes/COSMOS/VISION/WWW_05/illusions/OLIVER/Poggendorf_Oliver.html

  5. Percieved correct line Actual correct line http://www.chemistry.ucsc.edu/teaching/switkes/COSMOS/VISION/WWW_05/illusions/OLIVER/Poggendorf_Oliver.html

  6. Color = no effect Black Orange Cyan Orientation = no effect Vertical Horizontal

  7. Angles do have an effect 10° lateral - - - + + + - - - Inhibition

  8. Conclusions from Poggendorf Experiment Results can be skewed by the way an experiment is set up Orientation of the box does not affect a person's perception of the line Angle of the line affects a person's perception of the correct line Color has no effect on angle perception

  9. Muller-Lyer Illusion

  10. 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

  11. 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°

  12. 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 65 20 100

  13. 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

  14. 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

  15. Conclusion: Poggendorf vs. Muller-Lyer • 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

  16. Acknowledgements Sally Robinson Kathy Cooksey Gene Switkes Hillary O’Bryan Jason Porter Test Subjects John Martin CfAO

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