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Perception and Pattern
Recognition
 What types of information do we use to
perceive the world correctly?
 What are the major theories about how we
recognize patterns?
 What are the strengths and weaknesses of
these theories?
Types of Perceptual Processes
• Bottom-up - work up from sensory info.
• Top-down - apply knowledge and experience
Top-Down Effects
 Chess masters remember chess board
patterns better than novices (Chase &
Simon,1973)
 Easier to recognize objects in context
(Palmer,1975)
C
Illusory Contours
Template Matching Theory
 Recognize patterns by matching stimulus to
template
 Works in price scanners
Problems with Template Matching
• Differences in orientation
• Differences in size
RR
• Differences in form
R R
R
R
R
Feature Analysis
 Identify simple features of patterns
 Combine features into complex patterns
 Hubel & Wiesel (1965) found feature detector
neurons in cats
 Visual search: easier to find target when it
doesn’t share features with the background
(Neisser,1964)
Find the Z
Treisman’s Feature Analysis
Theory
 Preattentive Stage: detect visual features
 Pop-Out
 Illusory Conjunctions
 Focused Attention Stage: combine features
into objects
Problems with Feature Analysis
 Two different patterns can have
the same features
 Patterns may not have any
features that are required
H
Gestalt Approach
 Law of Pragnanz
 Similarity
 Good Continuation
 Proximity
 Common Fate
 Familiarity
Good
continuation
Prototype Matching Theory
 Prototype - “best” or “typical”
representation of a pattern
 Stimulus is compared to prototypes
 Uncertainty in pattern recognition
 Pseudomemory (Solso & McCarthy,1981)
Study These Faces...
Which Did You See?
A
B
 A is the prototype; it was not seen.
 B was not seen.
 C was one of the original faces.
C
Evolutionary Psychology
 What problems must the brain solve to
perceive accurately?
 Figure-ground separation
 Inverse projection problem
 Occlusion
 Edge perception
Evolutionary Psychology
 How does the brain solve these problems?
 Top-down and bottom-up
 Heuristics
 Built-in brain organization
 Plasticity