Concepts and Knowledge Thomas G. Bowers, Ph.D. Penn State Harrisburg 2000

Concepts and Knowledge  We are now moving away from episodic memory to information –Described as semantic memories –Or, sometimes, context-free or generic memories

Concepts and Knowledge  What is a dog? –What we know is similar to a dictionary definition –The definition itself is not completely adequate

Concepts and Knowledge  More difficult concepts –What is schizophrenia? –What is truth? –Or virtue?  Wittgenstein (1953) wrote at length on the philosophical nature of these questions

Concepts and Knowledge  Game is a good example of a concept which does not allow ready definition  Question: How do we decide about a concept?

Concepts and Knowledge  Use Family Resemblances –“Fuzzy” logic or fit –There may be no definition No “necessary” conditions (shared by all) Or “sufficient” conditions (unique attributes)

Concepts and Knowledge  Prototypes are an alternative to definitions –An “average” or representative member of a class –Marked by fuzzy boundaries –Graded degree of membership i.e. a degree of dogginess

Concepts and Knowledge  How to test the prototype notion? –Sentence verification task –Assesses processing speed for categorical task –For example, “A chair is furniture” or “A collie is cat”

Concepts and Knowledge  Subjects are faster for true sentences  Subjects are faster for familiar categories  Subjects are slower for atypical examples

Concepts and Knowledge  We can also use a production task  Simply name as many birds as you can, as quickly as you can  Look for convergence with reaction time tasks

Concepts and Knowledge Typicality Ratings of Fruit and Bird

Concepts and Knowledge  Convergent evidence for prototypes –1. Sentence verification tasks (McCloskey & Glucksberg, 1979) –2. Production (Barsalou, 1985) –3. Picture identification (Smith, Balzano & Walker, 1978) –4. Explicit memory of membership (Rosch, 1975)

Concepts and Knowledge  Convergent evidence for prototypes –5. Induction - Inferences from typical to the whole, but not from atypical to whole –6. “Thinking about” categories

Concepts and Knowledge  Prototypes as heuristics –There may be gains in cognitive efficiency and economy –Problems can be solved by step by step algorithm Tedious, exhaustive, consider and rule out all choices –Heuristics - consider only general plan or strategy Efficient, may overlook possibilities

Concepts and Knowledge  Schema theory revisited –There is thought to be a network of associations –Related to each other by propositions –There is a network of relationships

Concepts and Knowledge Dog Cat Chase Agent Object Action

Concepts and Knowledge  More complex analysis is possible  Some theories attempt to take into account complex human relationships  Object Relations Theory