Semantic Memory and Concepts

Semantic Memory

• Semantic memory is a part of declarative (explicit) long-term memory that stores general facts and concepts about the world.
• It also includes knowledge of the meanings of words in a specific language.
• Individual elements like concepts and categories are the building blocks of semantic memory.

Concepts

• A concept is a mental representation of a category of objects.
• A category is a set of objects that belong together.

Theoretical Approaches to Defining Concepts

• Common-feature approach: Concepts are defined by their essential, shared features, allowing categorization by checking those features.
  • Example: "Fruit" is defined by being the ripe, reproductive body of a seed plant.
• Issues with the common-feature approach:
  • Difficulty identifying defining features for all concepts.
  • Even with features, some concepts are not easily classified, showing fuzzy boundaries.
• Prototype approach: Each category has a prototype, a central description representing the category in long-term memory.
  • To categorize, items are compared to the prototype, and a high level of match indicates family resemblance.
• Typicality effect: People are faster to identify typical members of a category compared to non-typical members (e.g. robin vs. ostrich).
• Limitations of prototype approaches:
  • Not all concepts have clear prototypes (e.g., abstract concepts, ad-hoc categories).
  • Prototype approaches don't fully capture expert evaluations of concepts, which involve more complex evaluations than feature matching.
• Exemplar approach: Instead of storing a single prototype, we store examples (exemplars) of the category in long-term memory, along with encounter frequency information.
  • Comparisons to these exemplars contribute to categorization.
• Comparing Exemplar and Prototype Approaches:
  • Both approaches contribute to category naming time (RTs), but exemplar scores showed a stronger correlation.
• Knowledge-based approach: Embodied representation with modality-specific spokes (sensory, motor, emotional, verbal) and a modality-independent hub for integrated information.
  • Emphasizes contextual variability (through spokes) and stability (through hub).

Theories of Semantic Organization

• Hierarchical approach: Concepts are organized in a hierarchy of generality, with superordinate (abstract), basic-level (balanced), and subordinate (specific) categories.
  • Example: "Furniture" (superordinate), "Chair" (basic), "Bar stool" (subordinate).
• Limitations: The three-level hierarchy is inflexible and arbitrary, and doesn't account for the diversity of real-world categories.
• Network-based approach: Semantic information is organized based on semantic relatedness in a semantic network.
  • Nodes represent concepts, and links connect related concepts.
  • Spread of activation: When a node is activated, activation spreads to connected nodes, enriching the meaning of the original concept.

Methods for Identifying Semantic Relationships

• Word association task: Participants provide associations to a given word.
• Feature listing task: Participants list features associated with a concept.
• Direct ratings of similarity: Participants rate the similarity between two concepts.
• Computational approaches: Analyze co-occurrence patterns of words in large datasets to calculate semantic vectors representing word meaning.

Combining Concepts

• Proposition: Combine concepts based on rules to create true or false statements.
  • Example: "Dr. Cynthia is a professor in the psychology department."
• Schema: Integrated packets of related propositions about the world, events, or people.
  • Example: "How to take public transport in Singapore."
• Stereotype: A type of schema containing negative overgeneralizations about a specific group of people.

Importance of Schemas

• Facilitate perception and memory: Schemas help recognize familiar objects and events quickly.
  • Example: Recognizing the card reader on a bus.
• Enable predictions and inferences: Schemas allow us to make assumptions about situations and people.
  • Example: Assuming a family with many pets is unlikely to be planning children.

War of the Ghosts

• Demonstrates how schemas influence memory by shaping recollection and interpretation.
• Reflects how personal schemas can influence understanding of social situations.
• Stereotypes can also influence the interpretation of events.