Types of Perceptual Processes Bottom-up - work up from sensory info. Top-down - apply knowledge and experience

Top-Down Effects u Chess masters remember chess board patterns better than novices (Chase & Simon,1973) u Easier to recognize objects in context (Palmer,1975) C

Illusory Contours

Template Matching Theory u Recognize patterns by matching stimulus to template u Works in price scanners

Problems with Template Matching Differences in orientation R R Differences in size R R Differences in form R R R R

Feature Analysis u Identify simple features of patterns u Combine features into complex patterns u Hubel & Wiesel (1965) found feature detector neurons in cats u 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 u Preattentive Stage: detect visual features Pop-Out Illusory Conjunctions u Focused Attention Stage: combine features into objects

Problems with Feature Analysis u Two different patterns can have the same features u Patterns may not have any features that are required H

Gestalt Approach u Law of Pragnanz u Similarity u Good Continuation u Proximity u Common Fate u Familiarity

Good continuation

Prototype Matching Theory u Prototype - “best” or “typical” representation of a pattern u Stimulus is compared to prototypes u Uncertainty in pattern recognition u Pseudomemory (Solso & McCarthy,1981)

Study These Faces...

Which Did You See? u A is the prototype; it was not seen. u B was not seen. u C was one of the original faces. A B C

Evolutionary Psychology u What problems must the brain solve to perceive accurately? Figure-ground separation Inverse projection problem Occlusion Edge perception

Evolutionary Psychology u How does the brain solve these problems? Top-down and bottom-up Heuristics Built-in brain organization Plasticity