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 R

R• Differences in size

R

R

• Differences in form RR 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 is the prototype; it was not seen. B was not seen. C was one of the original faces.

A B 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