Representation organization in LTM by alicejenny


									        Representation/organization in LTM

Typical empirical testing paradigm: propositional
verification task – rt to rose is flower, vs. rose is plant.
Set Theoretical Models: categorical – hierarchical
storage. Along with items, feature list are stored.
Decisions are made based on comparisons of feature
lists – feature overlap. Support found in some vs. all
comparisons and most sub vs. immediate super.
Problem with atypical category members (whale is
mammal vs. whale is animal).
     Categorical/Hierarchical Model of Memory

• Some birds are robins vs. all birds are robins
• Crow-bird; crow-animal whale-mammal; whale-
  animal (atypical problem)
        Representation/organization in LTM

• Semantic feature comparison model: two
  stage process – 1. General feature overlap; 2.
  (if necessary) comparison of defining features
• Characteristic vs. defining features
• Generally solves atypical category member
• Problem raised: cognitive economy
                    Encode comparison

Low overall                                            High overall
                  Compare all features
similarity                                             similarity
(rock is bird)                                         (robin is bird)
                                 similarity (ostrich
                                 is bird)

                 Compare just defining features
     Mismatch                                          Match

               Representation in LTM

• Network model (Collins & Qullian): retains
  categorical – hierarchical organization, but only
  unique features stored with each item. Items
  assumed to retain features of superordinate
  category members. Spreading activation key
  concept. Return of atypical category member
• Modified semantic network model (Collins &
  Loftus). – removes hierarchical assumption.
  Distance represents semantic relatedness
Collins & Quillian Spreading activation model
Modified Spreading activation model
              Representation in LTM

• Propositional network model: Memory
  composed of interconnect network of
  fundamental propositions
• Proposition: smallest unit of information that
  can be judged t/f; typically represents
  relationship between concepts.
      ACT* Propositional Network Model: J.R.
• Susan gave
  Maria, the
  president of
  the club, a
  white cat.

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