Longterm Memory

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Long-term Memory
Semantic memory. Integrating memory performance

• Brandon Beltz
• March 30, 2005

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Lecture Outline

• Semantic Memory
• Organization
• Semantic Network
• Nodes, pathways
• Role of activation
• Role of structure
• Propositions
• Memory Summary Accuracy
• Memory Test Sensitivity
• Autobiographical memory study.
• Types of Accuracy
• Reconstructive Memory
• Contrast with reproductive memory
• Schema, scripts
• Inaccuracies in Memory
• False Memories
• Suggestibility
• Overconfidence

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Semantic Memory
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Semantic Memory

• Memories of our general world knowledge.
• No feelings that memories happened to you.
• That is, we rarely remember the encoding event(s)
  of the memories.
• Not specific to time or place
• Contrast with episodic memory

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Semantic Memory

• Our memory has the potential to store large
  quantities of semantic knowledge
• The storage of these memories can be quite
  complex

http//www.zone38.net/blog/pics/
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Semantic Memory Organization

• How is semantic memory organized?
• What are some possible analogies we could use to
  understand this organization?

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Semantic Memory Organization

• We can turn to the organization of the brain
  itself for inspiration
• Neural networks.

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Networks

• What is a network?
• e.g. Computer networks (the internet), social
  networks
• Features of networks
• The components
• e.g. individual computers, people
• Interactions among the components
• e.g. data transfer (electric signals), speech
  (auditory signals)

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Semantic Networks(Collins Quillian, 1969-1971)

• Model of memory that represents interrelated
  concepts or knowledge.
• The components
• Nodes
• The interactions
• Activation of pathways

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Semantic Networks

• Nodes
• Represent words or ideas

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Semantic Networks

• Pathways
• Associations among nodes
• Indicates relationships
• Property
• Specific property of a concept/node
• Isa
• Is an example of
• fits within larger concept/node

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Semantic Associations

• How do two or more words/concepts become
  associated with one another?
• Those words/ concepts frequently encoded and
  retrieved together
• similar process to classical conditioning
  (Pavlovs dogs)
• Over time they become associated and a pathway
  forms in the semantic network.

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Semantic Networks Activation

• Semantic networks a part of LTM
• When we need information, parts of the network
  are activated into working memory.

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Activation

• Walking to class, I see something small and red
  in a tree
• The nodes for red, small, and tree become
  activated
• and I recognize a cardinal

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Spreading Activation

• The activation spreads along the pathways of a
  node activating associated nodes.

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The Structure of Networks

• Structure formed by
• Numbers of nodes
• Numbers of pathways between nodes
• Distance between nodes

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Social Networks

• What role does the structure play in this
  network?
• What if Taylor wanted to meet Pat?

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Semantic Networks

• What role does the structure of the semantic
  network play?
• Semantic relatedness
• Activation and priming

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Semantic Relatedness

• The degree of relatedness between two nodes in
  the network
• Determined by their distance in the network.
• i.e. how many nodes exist between the two
• Nodes close in meaning/ highly related are stored
  close together in memory.
• e.g. doctor, nurse
• Unrelated nodes are far away.
• e.g. doctor, meteor

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Activation and Priming

• There is a limit to the amount of activation that
  can occur in the network
• (remember the limits of short-term, working
  memory)
• The structure of the network affects where the
  activation spreads and what does or does not get
  primed

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Lexical Decision Task

• vimp
• valve
• king
• swim
• sleep
• bed

• time
• flud
• book
• horse
• foot
• shoe

No
Yes
Yes
Semantically related sets of prime-target pairs
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Activation and Priming Facilitation

• Lexical Decision Task
• stimulus1 bird
• bird is activated in the network
• activation spreads
• associated nodes become primed
• stimulus2 cardinal
• cardinal is already partly activated
• Little further activation is required
• Later stimulus processing is facilitated (e.g.
  faster reaction time)

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Activation and Priming Inhibition

• Lexical Decision Task
• stimulus1 bird
• bird is activated in the network
• activation spreads
• associated nodes become primed
• stimulus2 toenail
• Toenail is a further distance from bird than
  cardinal
• Activation is already dispersed across nodes
  associated with bird
• Activation must cross further distances to reach
  target
• Later stimulus processing is inhibited (e.g.
  slower reaction time)

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Propositions

• Basic semantic units that encode meaning.
• Represent simple sentences or ideas
• The smallest unit one can make true/false
  judgements about.

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Pathways and Propositions

• Pathways connect two nodes together to form
  propositions.
• ISA pathways express category membership (e.g.,
  A robin is a bird).
• Property pathways express properties that
  concepts possess
• e.g., x has the property of y
• a cardinal has the property of wings

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Comparing Network and Propositional
Representations
Network Representation
Propositional Representation
property
relation
cardinal
recipient
cardinal
agent
true/ false?
Bottom line Propositions allow richer
representations of relationships between nodes.
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Are Propositions Real?Sachs (1967)

• Subjects read text passages
• They were tested for critical sentences in the
  passages at various time intervals.
• Results
• Subjects quickly lost information about the
  actual verbatim string of words they heard
• But, they retained the sentences meanings. (That
  is, they remembered the gist of the critical
  sentences, but forgot the syntax)

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Strengths of Propositions

• More accurately reflect the meaning of sentences.
• Reflect reconstructive memory processes (which we
  will discuss soon)
• Ignore the surface form of sentences
• Can construct complex sentences based on simpler
  propositions.

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Memory Summary

• Just how accurate is our memory
• and why does it matter?

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Combining Episodic and Semantic Memory

• The everyday operation of long term memory
  requires the continual, coordinated interaction
  between these two memory systems.

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Sensitivity of Memory Measures

• Recognition
• Recall

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Memory AccuracyAutobiographical
Memory(Bahrick, et al., 1975)

• Study conducted testing peoples memory for high
  school classmates names and faces.
• Subjects
• 400 people
• Ages from 17 to 74 (memory up to 57 years)
• Compared memory accuracy for different types of
  memory tests.

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Memory AccuracyAutobiographical
Memory(Bahrick, et al., 1975)

• Recognition
• Name recognition
• Picture recognition
• Picture matching
• Name matching
• Recall
• Picture cuing
• Free recall

http//www.qeliz.ac.uk/psychology/
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Memory AccuracyAutobiographical
Memory(Bahrick, et al., 1975)
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Sensitivity of Memory Measures

• So, recognition is relatively good over the years
• However, many situations dont facilitate
  recognition
• In the real world, just how accurate does our
  memory need to be?

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Types of Accuracy

• Technical Accuracy
• Recalling or recognizing exactly what was
  experienced.
• (generally quite poor)
• Content Accuracy
• Recalling or recognizing the meaning or content
  (the gist) of what was experienced.
• (generally quite accurate)

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Types of Memory(based on accuracy)

• Reproductive
• Reconstructive

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Reproductive Memory

• Highly accurate, verbatim memory of
  events/information.
• e.g. photographic memory computer memory
• We all wish our memories were like this, but
  common experience shows otherwise
• Why arent our memories reproductive and perfect?
  There has to be a downside to this.
• Storage and retrieval costs
• Practical time span that information is relevant
  and useful.
• e.g. How likely is the fact that I know eye
  saccades typically last for 25 ms going to
  benefit me 5 years from now?

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Reconstructive Memory

• Memories are interpreted in terms of prior
  knowledge.
• We reconstruct what probably happened
• That is, memories are not simply pulled out of
  memory in the exact way they were encoded.
• Role of schemas and scripts in this process

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Reconstructive Memory

• Schema
• A memory representation containing general
  information about an object or an event.
• It contains information representative of a type
  of event rather than of a single event
• Default values
• Script
• A type of schema that describes a series of
  events

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Inaccuracies in Memory

• False memories
• Source misattribution
• Suggestibility
• Overconfidence in Memory

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False Memories

• In the previous memory experiment, did you
  remember the word sleep?
• Was it actually on the study list?
• How confident are you?
• Perhaps the word was not on the list, but was
  primed by the other words

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Memory Experiment

• blanket
• doze
• slumber
• snore
• nap
• peace
• yawn

• bed
• rest
• awake
• tired
• dream
• wake
• snooze

The words you saw previously
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Source Misattribution

• The inability to distinguish whether the original
  event or another event was the source of the
  information.

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Leading Questions and Suggestibility(Loftus
Palmer, 1974)

• Subjects saw the same film of a car accident
• Later, different subjects were asked
• How fast were the cars going when they
• smashed?
• collided?
• bumped?
• hit?
• contacted?

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Leading Questions and Suggestibility (Loftus
Palmer, 1974)

• Subjects estimates of speed varied with the verb
  they were tested with.

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Leading Questions and Suggestibility (Loftus
Palmer, 1974)

• Two weeks after the film Did you see the broken
  glass
• (note No glass was present in the original film)?

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Possible Interpretations

• Memory Impairment
• A genuine change in memory of an experienced
  event as a function of some later event.
• The Response Bias Explanation
• No memory impairment subjects use the verb to
  infer that the cars must have been traveling
  faster (or slower) than previously remembered.
• reconstructive interpretation

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Misinformation Acceptance

• Accepting additional information as being part of
  an earlier experience without actually
  remembering that information.
• (closely related to suggestibility)
• Did I remember the car was speeding because it
  was, or because the policeman suggested it was?

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Overconfidence in Memory

• What factors influence the confidence in my
  memory accuracy?
• Source Memory (Memory of the exact source of the
  information)
• Speed of Processing
• (the faster something comes to mind, the more
  confident I am it is accurate)

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Seven Sins of Memory Schacter (1999)
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Questions to ponder

• What situations demand high technical accuracy?
• What can people do to improve their memory in
  those situations?
• Is our memory good enough for those situations
  that do not require technical accuracy?

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Announcement Memory Readings

• Mar 2 Short Term Working Memory
• Ashcraft Chapter 5
• Mar 9 Long-term Memory (encoding)
• Willingham ch 5 (copy available from my mailbox)
• Mar 23 Long-term Memory (retrieval)
• Willingham ch 6 (copy available from my mailbox)
• Mar 30 Long-term Memory (semantic memory and
  memory summary)
• Ashcraft Chapters 7, 8