Psych 352 - Class 12
Semantic Memory

Semantic Memory
     permanent store of general world knowledge

How is semantic memory organized?
 
Write down as many words as you can think of that come to
mind when I say the word YELLOW

   What are the most common words that come to mind? 
          Words related to the meaning of the word

Animal Example

    What words come to mind?    
    The most FREQUENT or TYPICAL

Semantic memory is organized in terms of the meaning and use of concepts

Three Models of Semantic Memory

1. Hierarchical Network Model (Collins & Quillian)
        Categorical hierarchy
        Cognitive Economy
                properties are linked only once at highest relevant level
        Spreading Activation

        Explains canary is a bird faster than canary is an animal
                canary signs faster than canary has skin
                (hierarchy effects)
        BUT not penguin is a bird slower than canary is a bird 
                (typicality effect)
        OR why whale is a fish is so slow (similarity effect)

2. Feature Comparison model
        concepts are organized as lists of features
        compare and get overlap score
        high overlap -- match
        low overlap -- no match
        medium overlap -- look for defining feature
        if definitive feature -- match
        if not - no match

        explains why penguin is a bird is slower than canary 
                (typicality effect)
        and why whale is a fish is slower than walrus is a fish
                (similarity effect) 
        but not set size effects
        (poodle is a dog faster than squirrel is an animal)
        or priming
        (rooster is a bird is faster after canary is a bird)

3. Revised Network models
        Nodes and Links
        Spreading Activation
        Explains typicality effects through Semantic distance
        Explains set size through FAN EFFECT (the more connections from
        each node, the less activation goes to each surrounding node)
        Explains Priming (through leftover activation to related concepts)

4. Connectionist model
        Basically the same as revised network except
        uses changes in the strength of links (connections) to show
        "semantic distance" (so penguin - bird link is weaker than 
        canary - bird link)
        AND has INHIBITORY links which allow the connectionist model to
        explain similarity effects (whale is a fish takes longer becuase
        so many fish properties are activated -- but eventually the 
        "bears live young" node will inhibit the "fish" related
        nodes and "mammal" will win