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Prof. Greg Francis
1PSY 310: Sensory and Perceptual Processes
Purdue University
Gestalt Psychology
PSY 310
Greg Francis
Lecture 14
This is a real object!
Purdue University
Wilhelm Wundt
Established the first true psychology laboratory in 1879 University of Leipzig (Germany)
Tried to identify basic elements ofperception
Structuralism
Similar to approaches in chemistry/physics
Find basic elements of matter (molecules)
Find basic elements of molecules (atoms)
Find basic elements of atoms (protons, electrons)
Find basic elements of….
Along the way you learn about how the basic elementscombine to have different properties
Prof. Greg Francis
2PSY 310: Sensory and Perceptual Processes
Purdue University
Structuralism
The basic idea is the perception is based onsensations
Look at the title of your textbook and this class!
Sensations are supposed to be simpler responsesto stimuli
Sensations are identified by introspection
“Looking” inward to identify the basic elements of theexperience
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Structuralism
If you take a bite of an apple, you might describe its basicsensations as
Cold, sweet, crisp
It would be a mistake to refer to it as
apple
Prof. Greg Francis
3PSY 310: Sensory and Perceptual Processes
Purdue University
Structuralism
If you could do this for lots of people and lots of stimuli, youmight identify the basic sensory elements of many differentperceptual experiences
Scientific reductionism
It never really worked out
Different people report different basic sensory elements
No set of basic sensory elements seemed to cover lots ofdifferent perceptual experiences
The goal of reduction is still a strong part of perception, butnot along these lines
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Other problems
Some percepts seem problematic for thestructuralist approach
In structuralism, percepts are built of up sensations
So sensations must be necessary to produce percept
What about a stimulus like this?
What sensation contributesto the perception of theillusory contour?
Prof. Greg Francis
4PSY 310: Sensory and Perceptual Processes
Purdue University
Other problems
Likewise, there are stimuli where presumablysensations are being gathered, but they do not giverise to a percept
Motion Induced Blindness movie
For that matter, one seems to get entirely new kindsof perceptual experiences from some stimuli
Apparent motion (demo)
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Ambiguous stimuli
There are thousands of stimuli that can be interpreted indifferent ways
Presumably they produce the same sensations, but differentpercepts
Prof. Greg Francis
5PSY 310: Sensory and Perceptual Processes
Purdue University
Ambiguous stimuli
There are thousands of stimuli that can be interpreted indifferent ways
Presumably they produce the same sensations, but differentpercepts
Find the man playing the flute
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Ambiguous stimuli
There are thousands ofstimuli that can beinterpreted in different ways
Presumably they producethe same sensations, butdifferent percepts
Find the Dutch girl
Prof. Greg Francis
6PSY 310: Sensory and Perceptual Processes
Purdue University
Ambiguous stimuli
There are thousands of stimuli that can be interpreted indifferent ways
Presumably they produce the same sensations, but differentpercepts
It’s not just clever drawings
Much of perception involves ambiguity
More than you realize
Motion
noWobbleGlobe.mov
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Gestalt Psychology The structuralists recognized these kinds of problems for
their approach, but they thought one could eventually dealwith them
Other people advocated an entirely different approach German scientists (Wertheimer, Koffka, Kohler) Gestalt is a German word that roughly means “whole” Gestalt psychologists suggested that understanding
perception could not be done by breaking it down into parts,but by considering the whole experience The whole is different than the sum of its parts.
One task of perception is to identify how to organize different partsof a visual scene
How to identify objects?
Prof. Greg Francis
7PSY 310: Sensory and Perceptual Processes
Purdue University
Perceptual organization What about the image or the visual system allows you to correctly
group different parts of the scene into objects? Similarity: color, texture, orientation Position Familiarity
Gestalt “laws” of perceptual organization
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Similarity Can isolate effects
Prof. Greg Francis
8PSY 310: Sensory and Perceptual Processes
Purdue University
Position Can isolate the effect
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Familiarity Having seen this image before, your perceptual organization is
different than the first time
Prof. Greg Francis
9PSY 310: Sensory and Perceptual Processes
Purdue University
Good continuation Object have boundaries Generally the boundaries run smoothly
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Good continuation Object have boundaries Generally the boundaries run smoothly
Prof. Greg Francis
10PSY 310: Sensory and Perceptual Processes
Purdue University
Good continuation Object have boundaries Generally the boundaries run smoothly
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Common fate Motion in a common direction is one example Can be more complicated than just direction Biomot.mov
Prof. Greg Francis
11PSY 310: Sensory and Perceptual Processes
Purdue University
Pragnanz “Good figure” Law of simplicity
The percept you see should be the simplestinterpretation of the scene
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Gestalt Laws They are not really laws, but suggestions about
what the visual system might be doing Most people do not really believe them in the
same way we believe the laws of physics or thelaw of natural selection
In fact, it is fairly easy to show that the Gestaltlaws are not anywhere near a completedescription of perceptual organization
Prof. Greg Francis
12PSY 310: Sensory and Perceptual Processes
Purdue University
Impossible figures What is the percept of this image?
Is this “good figure”?
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Impossible figures This is a
photograph ofa real object
Do you see itin the“simplest” waypossible?
Prof. Greg Francis
13PSY 310: Sensory and Perceptual Processes
Purdue University
Impossible figures This is a
photograph of areal object
Do you see it inthe “simplest”way possible?
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Conclusions Structural psychology
Gestalt psychology
Rules of perceptual organization
Impossible figures
Prof. Greg Francis
14PSY 310: Sensory and Perceptual Processes
Purdue University
Next time
Perceiving objects
Figure-ground relationships
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