how do we see objects? object perceptionrachtma8/psy214/files/l08.pdf · julian beever . 2 10/10/11...
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Object Perception
Chapter 5
How do we see objects?
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Ambiguous retinal image
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Artist: Julian Beever
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How do we see objects?
1. Why does the visual system respond best to specific types of stimuli?
2. How do we separate figure from ground?
3. How do we recognize objects from different viewpoints?
4. How does the brain process information about objects?
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Why does the visual system respond best to specific types of stimuli?
• Regularities in the environment
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Why does the visual system respond best to specific types of stimuli?
• Regularities in the environment – e.g., oblique effect – Causes?
• Gestalt heuristics are reflected in environmental objects
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Gestalt approach
Heuristics of perceptual organization
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Gestalt approach
– Pragnanz / simplicity – Similarity – Good continuation – Proximity / nearness – Common fate – Meaningfulness /
familiarity – Closure – Parallelism
– Symmetry – Common region – Uniform
connectedness – Synchrony
Heuristics of perceptual organization
Handout
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How do we see objects?
1. Why does the visual system respond best to specific types of stimuli?
2. How do we separate figure from ground?
3. How do we recognize objects from different viewpoints?
4. How does the brain process information about objects?
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Figure-ground segregation
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Figure-ground segregation
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Figure-ground segregation
5 Factors that determine which area is figure:
– Elements located in the lower part of displays
– Units that are symmetrical
– Elements that are small
– Units that are oriented vertically
– Elements that have meaning
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Figure-ground segregation - �Neural evidence
• V1 neurons are early in the nervous system
• Reveals both feed-forward & feed-backward communication in the system
• It demonstrates contextual modulation
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How do we see objects?
1. Why does the visual system respond best to specific types of stimuli?
2. How do we separate figure from ground?
3. How do we recognize objects from different viewpoints?
4. How does the brain process information about objects?
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Recognition by components theory
• Biederman: “We identify objects by their geometric shapes”
• These parts/shapes are relatively easy to detect regardless of orientation
• Called geons
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Geons
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Evidence for Geon theory
• Objects are easier to recognize if you can discriminate different geons
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How do we see objects?
1. Why does the visual system respond best to specific types of stimuli?
2. How do we separate figure from ground?
3. How do we recognize objects from different viewpoints?
4. How does the brain process information about objects?
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How does the brain process information about objects?
• Binocular rivalry exp’t (butterfly/sunburst) – Different pictures shown to each eye
– Record from neuron in monkey IT cortex
– Firing was vigorous for only the butterfly