Sensation/Perception
1. Vision
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not hearing,
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smell,
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taste,
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heat,
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touch,
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orientation in space,
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body position,
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pain...
2. The S-R Sequence:
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Energy ->
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Specialized Receptors ->
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Specific Nerves ->
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Higher Integration by Brain ->
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Action
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Unconscious,
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Conscious Experience
3. Visual Receptors:
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Rods and Cones (B,G,R)
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in the Retina
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Clustered in and around the Fovea
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Facing away from the light!!
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Stimulated by the Retinal Image
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upside down and backwards!!
4. Receptive Fields and Visual Nerves
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Specific Visual Nerves derive from
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Specific Areas of Retina.
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Information = Rate of Firing (Base-rate).
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Excitatory and Inhibitory Influences:
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Center-Surround ("Doughnut") Receptive Fields
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On-Center Nerves.
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Fire Fastest for Small Spot of Light.
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Also Off-Center Nerves.
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Fire Fastest for Large Area of Light.
5. "Bottom Up" Processing in the Visual Cortex
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Sensory Nerves provide the input for
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Feature Detector Cells (e.g., Edge at Angle X in Area Y)
and
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Higher Order Feature Detector Cells (e.g. Edge at Angle X
Somewhere!)
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Features Combine into a Form (e.g., Letter T Somewhere!)
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Motion Detectors ("And it's coming at us fast!!!")
6. "Top Down" Processing is also occurring.
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Your Perceptual Hypothesis:
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The overall pattern of sensory activity (Proximal Stimulus)
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Suggests the Form (your Perceptual Hypothesis)
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of the object out there (Distal Stimulus)
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Gestalt Principles of Organization:
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Figure/Ground.
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Grouping by Proximity
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by Closure
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by Similarity
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by Simplicity
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by Continuity
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e.g., Perceived Motion in a rapidly changing display.
7. Seeing things in 3-dimensions (Depth Perception).
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Binoculary Cues:
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Retinal Disparity (Stereopsis)
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Your two eyes have different views
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They are combined in the brain
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You "see" as though through one eye
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You "react" on basis of the two eyes.
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Convergence Angle (0-20 feet only).
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Monocular Cues:
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Accomodation
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Lens adjustment for clear image
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Only helps within 5-10 feet
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Relative Motion (Motion Parallax)
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Objects move or You move
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Close objects: Fast and opposite direction
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Far objects: Slow and same direction
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Pictorial Cues
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Interposition
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Light and shadow
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Linear Perspective, Relative Size, Texture, Height in plane.
8. Seeing Constancies in a Changing Display
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Brightness Constancy as the clouds go by...
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Size Constancy as a person approaches...
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Shape Constancy as your viewing angle changes...
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Color Constancy as the Color Wheel Turns...
9. Optical Illusions
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Angular Displacement: Poggendorff, Top Hat, Zollner
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"False Depth": Ponzo, Müller-Lyer, Moon
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Impossible Figures
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Carpentered World creates some...
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http://www.illusionworks.com