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Knowledge. information that is gained and retained what someone has acquired and learned organized in some way into our memory . Semantic Organization. put items that are related in some way into a cluster or a group.

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Presentation Transcript
knowledge
Knowledge
  • information that is gained and retained
  • what someone has acquired and learned
  • organized in some way into our memory
semantic organization
Semantic Organization
  • put items that are related in some way into a cluster or a group.
  • Cognitive Models - assume that detailed congitive structures represent the way semantic info is organized in memory
semantic memory cognitive models
Semantic Memory: Cognitive Models
  • Set-theoretical model
  • semantic feature-comparison model
  • network models
  • propositional networks
how to study semantic memory
How to study semantic memory
  • Association Tasks:
    • Free association: Used by Freud to study personality, but may tell us more about the structure of knowledge.
    • Category association: People are asked to give associates to a category name.
      • fruit: _________
      • fruit: a ________
how to study semantic memory1
How to study semantic memory
  • Tip of the tongue (TOT):
    • A sensation we have when we are confident we know a word we are searching for, but we are unable to recall it
    • Brown & McNeill (1966) research

1.read definitions of infrequent words

2.subjects asked to raise hands when they had a TOT

3.subjects then asked:

What is a similar word? What does the word sound like?

How many syllables?What is the word’s first letter?

4.Results: subjects often could supply partial information

how to study semantic memory2
How to study semantic memory
  • Sentence verification task:

Present sentence: "Is a robin a bird?"

Measure RT to correctly respond

  • Category verification task:

bird-robin ("yes")

bird-tree ("no")

Measure RT to correctly respond

how to study semantic memory3
How to study semantic memory
  • Lexical Decision (word/non word) Task:

Present a word (brain) or a non-word (shup).

Ask subjects to decide, as quickly as possible, if the item is a word.

RT tells us how long it takes subjects to search their mental dictionary.

set theoretical model
Set-theoretical model
  • Concepts in memory are collections (sets) of info.
  • Sets include:
    • instances of a category
      • category car has instances of Volkswagon, Saab, Mercedes,…
    • attributes or properties of a category
      • category car has properties of tires, engine, trunk, metal, windshield…
set theoretical model1
Set-theoretical model
  • Retrieval is a function of verification
    • must search through 2 or more “sets” to find overlapping information
    • more overlap = quicker decisions
feature comparison model
Feature Comparison Model
  • Basic Assumptions
    • Concepts are represented as a set of features, similar to Set-Theoretical model
    • unlike previous model, differentiates between:

1. Defining features (essential components)

2. Characteristic features (accidental, not always present)

    • verification is based more on defining features
feature comparison model2
Feature Comparison Model
  • Features are ordered according to "definingness"

characteristic featuresdefining features

birds fly birds have wings

birds sing birds have feathers

  • Relations between concepts computed based on shared features
feature comparison model3
Feature Comparison Model

Predictions:

1. Category size effect:

A robin is a bird. vs. A robin is an animal.

A dog is mammal. vs. A dog is an animal.

2. Typicality effects

A robin is a bird. vs. A penguin is a bird.

3. Quick rejection of false sentences:

A bat is a bird vs. A pencil is a bird

feature comparison model4
Feature Comparison Model
  • Problems:

1.Defining Features?

2.Semantic Priming?

3.Quick rejection of false sentences?

people are trees

a bat is a bird

a dog is a cat

network models
Network Models
  • Hierarchical Network Model -Collins and Quillian - early work
  • Spreading Activation Theory - Collins and Loftus
hierarchical network model
Hierarchical-Network Model
  • Representational Assumptions
    • hierarchically organization of concepts
    • cognitive economy: properties are stored at the most general, or highest level possible.
  • Processing Assumptions:
    • intersection search: enter the network at two concepts, and search for a connection.
    • type of connection determines yes/no response
hierarchical network model2
Hierarchical-Network Model
  • Tests of the model:
    • Category-Size Effect:

compare: A robin is a bird.

to: A robin is an animal.

    • Cognitive Economy:

compare: A bird has feathers

to: A bird has skin.

hierarchical network model4
Hierarchical-Network Model
  • Challenges to the Hierarchical Assumption:

1) reversals of the category size effect

A dog is a mammal vs. A dog is an animal.

2) typicality effects:

A robin is a bird. vs. An ostrich is a bird.

  • Challenges to Cognitive Economy
  • Negative sentence RT’s not predicted by the model
spreading activation
Spreading Activation
  • New assumptions:

1.Not hierarchical: length of links represent degree of relatedness. Search time depends on link length

2.Spreading Activation: retrieval (activation) of one of the links lead to partial activation of connected nodes. Degree of activation decreases with the distance.

3.Activation decreases with time.

spreading activation2
Spreading Activation
  • New predictions:
    • Typicality effects:
      • A robin is a bird. vs. A chicken is a bird.
    • Semantic Priming:

type of trial prime target RT

related prime bread butter 600

unrelated prime nurse butter 670

propositional network models
Propositional Network Models
  • HAM and the representation of Knowledge (Human Associatve Memory)
  • ACT (Adaptive Control of Thought