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

2. 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

3. 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

4. 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

6. Add Context: Top-Down “Rat Man”

7. 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

8. 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

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

11. 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

12. 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

13. 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

14. 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

16. 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

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

18. 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

19. 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

20. 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.

22. 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