Theories of Perception Bottom-Up Approaches (Direct) Top-Down Approaches (Constructive)

What is perception? Is it too simple to say we associating what is seen with what is remembered? This is direct perception Four types of bottom-up perception Template theories Prototype theories Feature theories Structural-description theories

What is direct perception? James Gibson Sensory information (contextual) is all we need to perceive No higher cognitive processes Existing beliefs Inferential thoughts intelligence Emphasized ecological validity Labs lack contextual information How do we know? Infant research They develop perception without higher level thinking

Lego Racer Pro/ENGINEER Parts is a good example of bottom-up design because the parts are first created and then assembled without regard to how the parts will work in the assembly

Add Context: Top-Down “Rat Man”

Template Theories Definition: highly detailed models for patterns we potentially recognize Stimuli  find template  Perception NOT an exact match Problems: TOO Rigid Our templates need to be adaptable We recognize the letter “A” despite its size How can we have templates for everything

Prototype Theories Definition: Not specific or rigid model Strengths We can form prototype even though we have not seen an exact example Solso & McCarthy, 1981 (Experiment) Showed them patterns (not prototype) Additional patterns + distracters Identify prototype + confidence in answers Implications: Never saw the exact prototype but were able to identify it because of previous patterns

Feature Theories Local vs. Global perception Supported by Biology Hubel & Wiesel Brain mapping Specific neurons for visual field Hierarchy: Simple and complex cells

Top-Down Processing Constructive Definition Conceptually driven Definition Perceiver builds (constructs) a cognitive understanding (perception) of a stimulus Use sensory information + other info Direct ONLY uses sensory information AKA  Intelligence perception Higher-order thinking is necessary

An example of top down processing: Even though the second letter in each word is ambiguous, top down processing allows for easy disambiguation based on the context

Examples What do you do if you see a stop sign that is missing a letter Construct  respond by stopping Apply to Gestalt Principles Size Shape Color

How do we form and test a hypothesis Sensation (sensory data) Prior expectations (expecting to see a friend we planned to meet) What we know (knowledge in memory) What we know about context (trains are on tracks, cars are not What we can infer (high-level cognitive processes) Based on data and what we know about data

Correct attributions based on visual information Unconscious inferences Unconsciously assimilate info from many sources Make judgments were are not aware we are making Correct perception requires…. Intelligence Thought Combine sensory info and knowledge from previous experience

Response to Direct Perception It doesn’t fully explain context effects Influence of surrounding environment on perception Context effects can be experimented on (lab)

Top-Down Research Palmer, 1975 Method: Experiment Results Control: appropriate context Kitchen  bread Exp: inappropriate context Kitchen  drum, mailbox Results Appropriate context recognized more rapidly

Configural-Superiority Effect improvement in discrimination performance resulting from the addition of informationless context stimuli A and B is aided by the addition of context C

Object-superiority effect identified a briefly flashed line segment more accurately when it was part of a drawing that looked unitary and 3-D Compared to if the line was in one of several less coherent flat designs.

Too Extreme Bottom-up Top-down Does not allow for past experience or knowledge Why do we store knowledge? Top-down Underestimates the importance of sensory information Gross inaccuracies in perception