Verbal Representation of Knowledge Knowledge: The storage, integration, and organization of information in memory Information is not equal to knowledge: Knowledge is organized information Declarative Knowledge: “That” Procedural Knowledge: “How”

Semantic Memory Concepts and Categories Knowledge without reference to how or where the information was acquired Encyclopedic information “Mental Lexicon" 20-40,000 words Rules

Two Types of Concepts Natural concept Artifact concept

Theories of Semantic Memory Organization Feature Comparison Model Prototype/Exemplar Theory Network Models PDP/Connectionist Models

Feature Comparison Model Concepts stored in memory in terms of a list of features or attributes e.g., bird has feathers can fly has a beak eats seeds has wings 2 types of features Defining Characteristic

Sentence Verification Task "A robin is a bird" vs. "A penguin is a bird“ Results indicate the “Typicality Effect”

Pros and Cons Typicality effect can be explained by feature lists Very few concepts have essential defining features

Prototype/Exemplar Theory Prototypes Categories are organized around a prototype (Rosch, 1975) An item is classified into categories by virtue of how similar the item is to a prototype Prototype of a category does not need to exist

Exemplars Specific examples of a concept learned New concept compared to other exemplars Barslou (1992) “bachelor”

Problems with Exemplars Would need to store many exemplars in memory Evidence still remains that we abstract out information from items coming into memory Current research: We probably use both

Network Models

Collins’ Model Collins & Quillian (1969); Collins & Loftus (1975) Network of nodes tied together by links and associations 2 types of links Superordinate (SA) Modifier (M)

Spreading Activation Links frequently traveled have stronger connection strengths

Adaptive Control of Thought (ACT, ACT*, HAM) Anderson (1996, 2000) Declarative Knowledge Procedural Knowledge Working Memory

Declarative Network – interconnected set of propositions Proposition – smallest unit of knowledge that can be judged true or false Links between propositions can become stronger over time

Example: Susan gave a cat to Maria. The cat was white. Maria is the president of the club.

PDP/Connectionist Models Mental processing units connected together Parallel operations Memories stored in connections Connections modified through connection weights A memory is not retrieved, it is reconstructed Default Assignment Graceful Degradation

Advantages May help explain the neural basis for memory Parallel operations Explains partial memories