L6: Knowledge in Semantic Memory Flashcards
How is general knowledge represented?
Represented in semantic memory, which stores the meanings of the concepts we know
What is a concept?
A mental representation representing a category of objects, where a category refers to a set of objects that belong together
Are concepts fixed or flexible?
Concepts are flexible
What happens when you lose your general knowledge?
Semantic Dementia (distinguished from Alzheimer’s Disease). Widespread and profound loss of memory for concepts and word meaning
What are the 4 approaches to concept organisation?
- Common feature approach
- Prototype approach
- Exemplar approach
- Embodied cognition approach
What is common feature approach?
Uses features that are necessary and sufficient for something to be an instance of a concept
Problems with common feature approach
Category boundaries sometimes too fuzzy to be handled by defining attributes
What is prototype approach?
All categories have a central description or prototype that stands for the whole category. An object is a member of a category if it shares many attributes with the prototype
What is concept of typicality effect?
Not every member of a category is equally representative (ie. penguin is a bird)
What is typicality effect?
In category verification, decisions are faster for more typical members.
Problems with prototypes
- Family resemblance scores did not predict typicality scores for members of goal-derived category.
- Evidence that best examples may be shaped by ideal instances rather than an average.
Exemplar approach
- No prototype or defining features
- Instead, there is a memory system storing large numbers of specific instances
- ie. for a ‘bird’ category, you have a store of all birds encountered in the past
Exemplars and Typicality Effect
Easier to verify that mynahs are birds compared to penguins since you have many more stored instances of mynahs
What is knowledge-based approach?
We are sensitive to the relationship between features
- Two features of an ax are sharp and dangerous
- An ax is dangerous because it is sharp
Disembodied mind
Body is divisible. Mind is indivisible. The mind of a man is entirely different from the body.
Embodied mind
Bodily experiences play a fundamental role in shaping thoughts, emotions and perceptions
Evidence for embodied cognition
- Perceptual anticipation theory says that the mechanisms used for visual imagery are the same as the ones used for perception
- Visual imagery activates similar areas in visual cortex as those involved in perception
- Processing concepts (eg. lick, pick, kick) activate relevant parts of the motor system
Cognitive representation of semantic categories
Categories are often organised into hierarchies: Superordinate - Basic - Subordinate ie. Animal - Dog - Chihuahua
- Basic-level categories (ie. chair) are most useful -> people most likely to rely on basic-level labels to name pictures
How can we assess semantic relatedness?
- Word-association task
- Feature overlap
- Distance rating task
What are propositions
Concepts can be combined into propositions, which is a configuration of concepts resulting in a true/false statement. Verbal messages are translated into a series of propositions that are stored in memory. The meaning is captured, but the specific words and order of words is lost. Frequent and familiar sequences of propositions can become grouped in schemas.
What is a schema?
A set of related propositions, which forms a packet of typical knowledge about the world, events or people
Schemas and semantic memory
We use schemas to store and retrieve information from semantic memory
Uses of schemas
- Allows us to form expectations and take appropriate actions in the world
- Prevents cognitive overload
- Helps fill in the gaps in what we read or hear
- Helps us when we perceive visual scenes
