Theories of Perception BottomUp Approaches Direct TopDown Approaches

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 1. Template theories 2. Prototype theories 3. Feature theories 4. 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 & Mc. Carthy, 1981 (Experiment) 1. Showed them patterns (not prototype) 2. Additional patterns + distracters 3. 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 – 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 1. Sensation (sensory data) – Prior expectations (expecting to see a friend we planned to meet) 2. What we know (knowledge in memory) – What we know about context (trains are on tracks, cars are not 3. 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 – 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 – 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