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
• A problem with a child’s
eye must be corrected
before the age of six
• If not, the weak eye will http://www.nei.nih.gov/nehep/summer03/
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/i
llusions/OLIVER/Poggendorf_Oliver.html
http://www.chemistry.ucsc.edu/teaching/switkes/COSMOS/VISION/WWW_05/i
llusions/OLIVER/Poggendorf_Oliver.html
Ratio of Percieved to
actual angle
Box Fill Color
1.5
Black
1.3
Orange
1.1
Cyan
0.9
Mean Black
Mean Orange
0.7
Mean Cyan
0.5
0
Black
1
Orange
2
Color
Ratio of Percieved to
actual angle
Box Orientation
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
Vertical
Horizontal
Mean Vertical
Mean Horizontal
0
0.5
Vertical
1
1.5
Shape
Horizontal
2
2.5
Cyan
3
4
Ratio Percieved to actual
angle
Angle of Line
1.4
1.2
1
0.8
0.6
0.4
0.2
0
10 Degrees
25 Degrees
39 Degrees
Mean 10
Mean 25
Mean 39
0
10
20
30
40
50
Degrees
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 http://www.pc.rhbnc.ac.uk/illusions/Image46.gif
always appear larger
– subconscious
• The area theory
– People try to match areas instead of
the length of lines
– subconscious
Ratio of Line Lengths
Results of the Change in Fin Angle
• Hypothesis: the smaller the fin angle, the stronger the
illusion
• Possible explanations
Ratio of Line Lengths with Differing Fin Angles
-Corner theory: the closer
to a corner, the sharper the
1.35
angle; the farther away the
1.25
corner, the more similar
1.15
the lengths of lines
-Area theory: the smaller
1.05
the angle, the more
0.95
dissimilar the areas
0.85
40
50
60
70
80
Degrees of Angles
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
Line Length
Ratio of Line Lengths with Differing Fin Lengths
1.30
1.25
1.20
1.15
1.10
1.05
1.00
0.95
0.90
0.85
0
20
40
60
80
100
120
Fin Length
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