Visual Visual Illusions: Illusions: Ponzo & Poggendorf Ponzo & Poggendorf Leo Do Beckie Aguirre Cluster 7
Visual Illusions: Visual Illusions: Ponzo & PoggendorfPonzo & Poggendorf
Leo Do Beckie Aguirre Cluster 7
OutlineOutline
What are visual illusions What are the Ponzo and Poggendorf Illusions? How are our illusions tested? Results
- how did everyone do?
- how did the variables affect what we saw? How did our illusions work? Conclusions
BackgroundBackgroundWhat are illusions?
– Visual Illusions occur when you “see” something differently than that which is actually there.
Who invented the Ponzo illusion?– Mario Ponzo in 1913.
Who invented the Poggendorf illusion?– Johann Poggendorf in 1860.
Visual Illusions also help us learn about our visual systems.
MethodsMethodsPonzo IllusionPonzo Illusion
3 variables:– Color of ties– angle of tracks– reference bar position
3 settings per variable3 attempts per setting11 subjects tested Harder than it looks
Reference barTies
Tracks
Measured bar
Color of TiesColor of Ties
0.85
0.9
0.95
1
1.05
1.1
1.15
Black Blue Gray
Color of Ties
Rati
o
The color of the ties does not appear to affect how well people can make the bars the same length.
Ponzo Illusion:Ponzo Illusion:Angle of TracksAngle of Tracks
Angle: 5 degrees Angle: 22 degrees
Less Depth More Depth
0.85
0.9
0.95
1
1.05
1.1
1.15
5 15 22
Angle of Tracks
Rat
io• As expected, the misperception increased as the angle of the tracks
increased from 5 to 15°.• However, the misperception decreased between 15 and 22° when
it appeared that the reference bar was further away.
(degrees)
Angle of Tracks
Less Depth More Depth
Ponzo Illusion:Ponzo Illusion:Reference Bar PositionReference Bar Position
Reference bar position: 50 units Reference bar position:120 units
Positions tested: 50, 72, 120 units
More distant Less Distant
Reference Bar PositionReference Bar Position
0.85
0.9
0.95
1
1.05
1.1
1.15
50 72 120
Reference Bar Position
Rat
ioPeople misperceive a larger difference in bar lengths when the reference bar is more distant from the measurement bar
More distant Less Distant
Why do we see the Ponzo Why do we see the Ponzo Illusion?Illusion?
Size Constancy & Perspective We expect an object that is
further away to appear smaller than the same object when it’s closer
We expect the reference bar to look smaller than the measurement bar because you think it’s further away.
ConclusionsConclusions Color of ties: No impact on subjects ability to make
bars the same length
Angle of tracks: Misperception initially increased with angle, but then unexpectedly decreased
Reference bar position: Harder to make bars same length when reference bar appears more distant
Most subjects averaged Ratio > 1
Size constancy and our past experience influence how we see this illusion
Our brains function with our eyes to make us see what we see
How the Poggendorf illusion How the Poggendorf illusion worksworks
There is a box in the middle of two lines which are connected even though it doesn’t look that way.
But the question is why is this misperceived?
Subjects were told to move the top line to where they think it is connected to the bottom line.
MethodsMethodsThe Poggendorf test
Variables tested:– Angle of the line– Height of the box– Line color– Border and box color
11 subjects were tested Each test was conducted three times
Poggendorf IllusionPoggendorf IllusionAngle of the lineAngle of the line
Reference angle: 20°Angles tested: 40°, 65°
Angle = 20°
Angle = 65°
ResultsResultsAngle of the lineAngle of the line
When the angle between the line and the box increases, the misperception of lining up the two lines decreases.
Height of the boxHeight of the box
Reference height: 50Height tested: 25, 75
Height = 25 Height = 75
Results of the box height
Changing the box height has little effect on subjects ability to line up the two lines.
Line colorLine color
Cyan lines
Reference: black line, cyan box
Tested: Cyan line, cyan box
Black lines
Results for line color
When the color of the line matched the color of the box, the subjects were able to line up the two lines more accurately.
Border and box colorBorder and box color
Red Border and Box
Reference: Line black, cyan border and box
Tested: Line black, red border and box
Cyan Border and Box
Results for box color
The misperception is somewhat smaller when the color changes from cyan to red.
How does the Poggendorf work?How does the Poggendorf work?
Hering Illusion• Acute angle dilation
• Our brains make small angles appear larger than they actually are.
• Subjects line up the two lines better when the angle is larger.
• Here is another illusion that works the same way - Hering illusion
How does the Poggendorf work?How does the Poggendorf work?
Hering Illusion• Acute angle dilation
• Our brains make small angles appear larger than they actually are.
• Subjects line up the two lines better when the angle is larger.
• Here is another illusion that works the same way - Hering illusion
ConclusionConclusion
I have learned that with the different variables, - angle of lines increased: subject misperception decreased - box height: No effect - line color: misperception lower for cyan line than black line - box color: misperception lower for red box than for cyan box
Illusions trick your brain into seeing something that is not actually present.
Your eye sees something that’s physically there, but your brain interprets it as something different.
Acknowledgements Acknowledgements Thank-you:
– Mr. Jason Porter (J “GheTto” Dawg)– Ms. Maribell, Mrs. Hilary, Mr. Gabe, Mr. Gary,
and– Dr. Gene Switkes– Ms. Pascha– Everyone from CFAO, and everyone from Cluster
7.
This work has been supported in part or full by the National Science Foundation Science and Technology Center for Adaptive Optics, managed by the University of California at Santa Cruz under cooperative agreement No. AST-9876783.