Visual Cognition (1) - Visual Cognition Perception &...

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Visual Cognition Perception & Pattern Recognition
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I. Modularity in the Visual Pattern Recognition System Pattern Recognition Words Objects Faces Living (or Animate) Non-living (or Inanimate)
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A. Konorski’s (1967) Visual Recognition Taxonomy Small, manipulable objects Larger, partially manipulable objects Non-manipulable objects Human faces
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Emotional facial expressions Animated objects Signs Handwriting Positions of limbs
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1. Domain-Specific Recognition Systems Faces Prosopagnosia Objects Agnosia Words Alexia B. Farah (1992)
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2. Dissociations in Neuropsychology IMPAIRED INTACT # Cases Faces Objects, Words 27 Faces, Objects Words 15 Faces, Ob, W none 22 Words Faces, Objects Not included Objects, Words Faces 16 Objects Faces, Words 1? Faces, Words Objects 1?
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3. Holistic vs.Decompositional Processing Tanaka & Farah (1992) Subjects taught to identify a set of faces + objects (e.g., houses) When tested with a PART from objects (e.g., door of a house), subjects better at recognizing than part of a face (e.g., nose) Faces less decomposable than objects 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% Faces Houses Isolated Part Whole Object
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4. Farah’s Conclusions Face recognition is holistic Word recognition is (more) decompositional Object recognition system shares strategies of both
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II. The Visual System A. The Eye Iris & Pupil Lens Retina Rods Cones
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Bipolar Cells Ganglion Cells Optic Nerve Optic Chiasm Lateral Geniculate Nucleus (LGN)
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B. Primary Visual Cortex On/Off Center Cells
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V1 receptive fields: response of a simple cell
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Feature Detectors/ Simple Cells, sensitive to Orientation Part of the VF Size
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V1 receptive fields: complex
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V1 receptive fields: response of a complex cell
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Complex cells sensitive to: Line Orientation Movement in a given direction
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Hypercomplex Cells have inhibitory regions at each end, thus Maximally respond to lines of a given orientation if they are not too long
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C. The Visual Brain
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Cortical Areas/Functions V1: Primary Visual Cortex V2: Relays visual signals to other areas V3: Form, & Motion (3a) V4: Form & Color Activated by objects but not scrambled objects (Grill-Spector, Kushnir, Hendler, Edelman, Itzchak, & Malach, 1998) V5: Motion
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V4: colour V5: Motion
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What does the Visual System have to accomplish? Distinguishing Figure/Ground
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Parsing complex scenes into individual parts or objects
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Recognition & Interpretation Necker cube
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-- both stimulus-driven (bottom-up) and memory-driven (top-down) processes are used Kaniza figures
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D. “What” & “Where” Systems (Mishkin & Appenzeller, 1987) Bifurcation of visual systems into --”where:” dorsal (occipitoparietal) pathway -- “what:” ventral (occipitotemporal) pathway
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Milner & Goodale Dorsal “where” is actually linked to action system
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III. Recognizing 2-D Stimuli
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A. Template Matching Theory 1.
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This note was uploaded on 12/17/2010 for the course PSY 43785 taught by Professor Reed during the Spring '10 term at University of Texas at Austin.