Transcript 2320Lecture21

Overview of Memory
RETRIEVAL
• Atkinson-Shiffrin Model
ATTENTION
Sensory
Signals
Sensory
Memory
Short-Term
Memory
Long-Term
Memory
REHEARSAL
Short-Term Memory
• process by which we hold information
“in mind”
Short-Term Memory
• process by which we hold information
“in mind”
• example: temporarily remembering a
phone number
Characteristics of STM
•
Duration? Capacity?
•
How could one measure these
parameters?
Characteristics of STM
•
Limited Duration
– Brown-Petersen Task:
• subject is given a trigram (e.g. C-F-W)
to remember
• vocal rehearsal is prevented by
counting backwards
• recall accuracy tested as a function of
retention interval
Characteristics of STM
•
STM
decays
over
seconds
Characteristics of STM
•
Limited Duration
– Brown-Petersen Task Interpretation:
rapid loss of information in STM (over a
period of seconds…much longer than
sensory memory)
Characteristics of STM
•
Limited Capacity
– How might you measure capacity?
Characteristics of STM
•
Limited Capacity
– George Miller
– Subject is given longer and longer lists of
to-be-remembered items (words,
characters, digits)
Characteristics of STM
•
Limited Capacity
– George Miller
– Subject is given longer and longer lists of
to-be-remembered items (words,
characters, digits)
– Result: Subjects are successful up to
about 7 items
Characteristics of STM
•
Limited Capacity
– What confound must be considered ?!
Characteristics of STM
•
Limited Capacity
– What confound must be considered ?!
– Recalling takes time !
Characteristics of STM
•
Limited Capacity
– What confound must be considered ?!
– Recalling takes time !
– It seems that the “capacity” of STM (at
least measured in this way) depends on
the rate of speech - faster speech leads
to apparently larger capacity
– Some believe capacity is “2 - 3 seconds
worth of speech”
Forgetting from STM
• Why do we “forget” from STM?
– Does the memory trace decay?
• not likely because with very small lists (like 1
item) retention is high for long intervals
Forgetting from STM
• Why do we “forget” from STM?
– Does the memory trace decay?
• not likely because with very small lists (like 1
item) retention is high for long intervals
– Instead, it seems that information “piles up”
and begins to interfere
Forgetting from STM
• Interference in STM is complex and
specific
Forgetting from STM
• Interference in STM is complex and
specific
• For example, severity of interference
depends on meaning
Forgetting from STM
• Interference in STM is complex and
specific
• For example, severity of interference
depends on meaning
– Subjects are given successive recall tasks
with list items from the same category (e.g.
fruits)
– final list is of either same or different
category - how is good is recall on this list?
Forgetting from STM
• Accuracy rebounds if category changes
Coding in STM
• How is information coded in STM?
Coding in STM
• Clues about coding in STM:
– # of items stored in STM depends on rate
of speech
Coding in STM
• Clues about coding in STM:
– # of items stored in STM depends on rate
of speech
– phonological similarity effect: similar
sounding words are harder to store/recall
than different sounding words
Coding in STM
• Clues about coding in STM:
– # of items stored in STM depends on rate
of speech
– phonological similarity effect: similar
sounding words are harder to store/recall
than different sounding words
What does this suggest about the nature of information in STM?
Coding in STM
• It seems that information can be stored
in a linguistic or phonological form
Coding in STM
• It seems that information can be stored
in a linguistic or phonological form
Must it be stored this way?
Coding in STM
• It is also possible to “keep in mind” nonverbal information, such as a map
Are there two different STM systems?
A Modular Approach to STM
Central
Executive
Articulatory
Loop
Visuospatial
Sketchpad
Experiment 1 in the article by Lee Brooks
demonstrates a double dissociation between
Articulatory Loop and Visuospatial Sketchpad
Working Memory “Modules”
• Lee Brooks: interference between different
representations in STM (Experiment 1)
– Memory Representation
• verbal task: categorize words in a sentence
• spatial task: categorize corners in a block letter
– Response Modality
• verbal response: say “yes” or “no”
• spatial response: point to “yes” or “no”
Working Memory “Modules”
• Verbal Task: indicate if each word is or is not
a noun
– “I went to the store to buy a loaf of bread.”
–N N
N N Y N N N Y N Y
Working Memory “Modules”
• Spatial Task: indicate if each corner points
outside
Y
Y
F
Y
N
Working Memory “Modules”
• In both tasks the information needed must be
maintained (represented) in working memory
Working Memory “Modules”
• Response Modalities:
Verbal
Spatial
Say: “yes” “no” “no”
Point to: Y or N
Y
Y
Y
Y
Y
N
N
N
N
N
Working Memory “Modules”
• Both response modalities also engage
working memory
Working Memory “Modules”
• Prediction:
– There should be interference when response
modality and task representation engage the
same module
– if there is only one kind of module, then there
should be interference between every pairing of
representation to response
Working Memory “Modules”
• result: a cross-over interaction (double dissociation
Performance
Verbal Representation
(categorize words)
Spatial Representation
(categorize corners)
Verbal
Spatial
Response Modality
Working Memory “Modules”
• Interpretation:
– supports notion of modularity in Working
Memory (visuospatial sketchpad /
articulatory loop)