LongTerm Memory

1
Long-Term Memory
Focusing on Memory Retrieval

• Brandon Beltz
• March 23, 2005

2
Lecture Outline

• The role of prior knowledge in encoding
• Memory retrieval
• Reliability of retrieval
• Measures of memory
• Sensitivity of measures
• Retrieval cues and memory test sensitivity
• Retrieval cues and the physical environment
• Identical cues, different memories
• Retrieval and prior knowledge
• Why do we forget
• Forgetting processes
• Occlusion
• Unlearning
• Decay
• Changes to target memories
• Inhibition

3
Why Do We Encode Information as We Do?

• Prior Knowledge (memories)
• Reduces what we must remember
• Guides the interpretation of details
• Makes unusual things stand out

Top-down processing
4
Prior Knowledge Reduces What We Must Remember

• Study of expert chess players
• Chase and Simon (1973)
• Expert level chess players and nonexperts asked
  to remember location of pieces on a chess board

5
Prior Knowledge Chess Example

• Expert players memory of location much more
  accurate
• Expert players able to chunk pieces into larger
  meaningful units using their prior knowledge
• Chunking helps reduce memory load

The red knight is protected by the red bishop
The red king is castled
6
Prior Knowledge Chess Example

• However, in later studies, experts memory was no
  different than novices when the piece locations
  were illegal and did not fit standard
  chessboard templates
• Illustrates important role of relevant prior
  knowledge

Illegal chessboard
7
Prior KnowledgeGuides the Interpretations of
Details

• Prior knowledge can be thought of as sets of
  related facts
• (i.e. knowledge is not a bunch of random facts
  thrown together)
• Facts can come in sets known as schema

8
Prior KnowledgeGuides the Interpretations of
Details

• 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

9
Prior KnowledgeGuides the Interpretations of
Details

• Default value
• A characteristic that is assumed to be true in
  the absence of other information.
• Example unless one is told otherwise, one
  assumes that a dog is furry furriness is a
  default value for dogs

10
Prior KnowledgeGuides the Interpretations of
Details

• Schemas aid in interpreting ambiguities of
  details
• What does the following ambiguous paragraphs
  refer to?
• The procedure is actually quite simple. First
  you arrange things into different groups. Of
  course one pile may be sufficient depending on
  how much there is to do. If you have to go
  somewhere else due to lack of facilities that is
  the next step, otherwise you are pretty well set.
  It is important not to overdo things. That is, it
  is better to do too few things at one time than
  too many. In the short run this may not seem
  important but complications can easily arise. A
  mistake can be expensive as well. At first the
  whole procedure will seem complicated. Soon,
  however, it will become just another facet of
  life. It is difficult to foresee any end to the
  necessity for this task in the immediate future,
  but then one can never tell.
• After the procedure is completed one arranges
  the materials into different groups again. Then
  they can be put into their appropriate places.
  Eventually they will be used once more and the
  whole cycle will then have to be repeated.
  However, that is a part of life.
• (Bransford and Johnson, 1972)

11
Prior KnowledgeGuides the Interpretations of
Details

• In the previous paragraphs accuracy was much
  improved if the subjects knew that the paragraph
  referred to washing clothes.

12
Prior KnowledgeMakes Unusual Things Stand out

• Prior knowledge helps us anticipate future
  events
• Knowledge about common events organized into
  scripts
• (Schank and Abelson, 1977)
• Script A type of schema that describes a series
  of events
• Example
• What happens in a restaurant
• What happens in class
• Studies show that memory is best for
• Details that are not part of the script (unusual
  things)
• Details relevant to the goals of the script
• Bower, et al. (1979)

13
Memory Retrieval
14
Process of Retrieval

• Retrieval cues come from a variety of sources
• External (environment)
• You leave a note for yourself
• Teacher asks you a question.
• Internal
• You remind yourself
• As we will see, this process is not so simple

Retrieval Cue
Association between cue and memory
Target Memory
15
Why is Memory Retrieval Unreliable?

• Sensitivity of memory measures
• Retrieval cues
• Retrieval cues a the physical environment
• Identical cues, different memories?
• Prior knowledge and retrieval
• Processes of forgetting

16
Measures of Memory(How we retrieve the contents
of memory)

• Recall
• Recognition
• Recall and recognition mostly refer to the types
  of tests we use to measure memory.
• In almost all laboratory experiments there are
  study and test phases.

17
Memory Recall

• Free recall
• No cues are provided
• (except maybe time and place of encoding)
• e.g., Tell me about what you did during Spring
  Break.
• Recall the items in any order
• Serial recall (see lecture 5)
• Cued recall
• Cues are provided but the target information is
  not present in the cue.
• e.g. On your first day of Spring Break you drank
  a lot of alcohol and

18
Examples of recall that you might recognize

• Free recall
• What is cognitive science?
• Cued recall
• The four major lobes of the brain are
• Fr____, Pa____, Oc____, Te_____

19
Memory Recognition

• Recognition
• In some tests, distractors are presented along
  with target.
• Identify the target from the distractors.
• In other tests, one item (either target or
  distractor) is presented by itself.
• Yes or No, do you recognize this item?

20
Memory Recognition
Study Phase

• Remember this face

21
Memory Recognition
Test Phase (with distractors)

• Did you see any of these faces earlier?

• In recognition tasks, people must identify
  targets
• and avoid distractors

22
Memory Recognition
Test Phase (single item)

• Yes or No did you study this face earlier?
• The famous pick up line Have we met before?

23
Example of recognition that you might recognize

• 7. The cell that is specialized for receiving
  and transmitting a neural impulse.
• a. Synapse
• b. Myelin
• c. Neuron
• d. Node

24
Sensitivity of Memory Measures

• Sensitivity the ability of a memory test to
  actually detect memories (assuming they have
  been stored).
• Generally, cued recall more sensitive (a good
  thing) than free recall.
• Generally, recognition more sensitive than
  recall.
• Subjects unable to recall general knowledge
  questions were able to recognize the answer 50
• Hart (1965, 1967)
• (Keep in mind, the details of encoding and the
  test conditions matter!)

25
Retrieval Cues the Physical Environment

• Does changes in the environment at encoding
  affect performance at retrieval?
• Important Studies
• Subjects tested on land and underwater after
  learning material on land or underwater.
• Godden and Baddeley (1975)
• Similar study in a college environment.
• Glenberg and Bjork (1978)

26
Retrieval Cues the Physical Environment

• In both studies, matching environments led to
  better performance.
• That is, the context of encoding seemed to affect
  retrieval.
• However, the effect is weak and probably depends
  on a match of thoughts at time of encoding and
  retrieval

27
Retrieval Cues Context

• Study Bilingual subjects (English-Russian)
  interviewed in both languages
• Subjects recalled different details of their
  pasts depending upon which language they were
  interviewed in.
• E.g. when interviewed in Russian, they recalled
  more details of when they lived in Russia and
  vice versa.

Marian Neisser, ?
28
Identical Cues, Different Memories?

• Often we encounter the same cue, but sometimes we
  retrieve different memories
• Why is that?

29
Identical Cues, Different Memories?

• Priming
• Later processing of a stimulus is improved
  (facilitated) or degraded (inhibited) due to
  previous exposure to another stimulus.
• Generally, the term priming refers to improved
  processing.
• Can occur when later stimulus is the same as or
  semantically related to a previous stimulus.

30
Priming

• Prime Stimulus presented earlier in time
• (should influence later stimulus processing)
• Target Stimulus that follows the prime
• (should be influenced by the prime)

31
Word Priming Example(Meyer, Schvaneveldt, 1971)

• Lexical Decision Task
• Participants shown two strings of letters
• strings can be words or nonwords
• Make a decision of whether both strings are words
  or not
• Real world-example
• Deciphering strings of letters on custom license
  plates

32
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
33
Lexical Decision Results
1200 1000 750 500 250 0
Reaction Time
Related Words
Unrelated Words
Nonword
34
Influences of priming

• Facilitation Prime decreases processing time of
  target.
• e.g. related words
• Inhibition Prime increases processing time of
  target.
• e.g. nonwords

35
Back to identical cue, different memory

• Sometimes we encounter the same cue
• But we retrieve a different memory
• Because one memory is more highly primed than
  another.

foot
shoe
ball
toe
36
Retrieval and Prior Knowledge

• Prior knowledge influences retrieval of typical
  events but not atypical ones.
• Study- Participants Recalled events of a story
• Bartlett (1932) War of the Ghosts
• On recall details were altered to make the story
  more coherent (process of reconstruction).

37
Retrieval and Prior Knowledge

• Reconstruction
• The idea that 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

38
Why Do We Forget?

• Processes of forgetting
• occlusion, unlearning, decay
• Changes to target memories
• Repression of memories
• Memory permanence

39
Process of Retrieval and Forgetting
Retrieval Cue
Association between cue and memory
Target Memory
40
Occlusion (interference)
Retrieval Cue

• One memory blocks (occludes) another memory.
• A form of interference.
• Occluding memory is often related to target
  memory.

e.g. What is the name of your significant other?
Occluding Memory
Target Memory
Taylor (ex)
Pat (current)
41
Unlearning
Retrieval Cue
Retrieval Cue

• Association between cue and memory weakened over
  time due to new learning.
• Cue practiced more often with new target.

e.g. What is the name of your significant other?
e.g. What is the name of your significant other?
New Target
Old Target
Pat (current)
Taylor (ex)
42
Decay
Retrieval Cue

• The association between a cue and memory and
  possibly the memory itself decay due to the
  passage of time.

e.g. What is the name of your significant other?
Target Memory
Taylor (ex)
43
Changes to Target Memories

• When a cue is given, it has the potential to
  activate any number of relevant memories
• Why is it that in most cases we are able to
  successfully retrieve the right target memory?

44
Changes to Target Memories

• Inhibition of memories
• Mechanism that suppresses unwanted memories
  triggered by a cue.
• Keeps unwanted memories from being retrieved
  instead of target memory.
• Inhibition studies
• Anderson, et al., 1994, 1995

45
Inhibition Study (Study Phase)
Category color pet
Items in Category red blue green orange cat dog f
ish bird
(Anderson, et al., 1994)
46
Retrieval induced forgetting(Practice Phase)

• Category
• color
• pet

• Items in Category
• red
• blue
• green
• orange
• cat
• dog
• fish
• bird

Category and half of all items
practiced Category and items not practiced
Practice session example cue color recall
red
(Anderson, et al., 1994)
47
Retrieval induced forgetting(Test Phase)

• Cue
• color
• pet
• pet
• color
• etc...

• Recall
• ?
• ?
• ?
• ?
• etc

(Anderson, et al., 1994)
48
Retrieval induced forgetting(Results)

• Category
• color
• pet

• Items in Category
• red
• blue
• green
• orange
• cat
• dog
• fish
• bird

Category and half of all items
practiced Category and items not practiced
Better recall or worse? Practiced items in
practiced categories Unpracticed items in
practiced categories Unpracticed items in
unpracticed categories
49
Retrieval induced forgetting(Results)
More Less
Number Words Recalled
Category Items
Practiced Practiced
Unpracticed Unpracticed
Practiced Unpracticed
(Anderson, et al., 1994)
50
Changes to Target Memories

• Why is it that in most cases we are able to
  successfully retrieve the right target memory?
• Inhibition of non-target memories!

Significant other?
Pat
Courtney
Taylor
51
Retrieval Summary

• Reliability of retrieval
• Measures of memory
• Sensitivity of measures
• Retrieval cues and memory test sensitivity
• Retrieval cues and the physical environment
• Identical cues, different memories
• Priming
• Retrieval and prior knowledge
• Why do we forget
• Forgetting processes
• Occlusion
• Unlearning
• Decay
• Changes to target memories
• Inhibition