Transcript 2320Lecture23

Plans:
•Read About False Memories (Beth Loftus) for Thursday (April 7th)
•Read About Amnesia (Oliver Sacks) for Tuesday (April 12th)
•Read about Subliminal Messages (Vokey and Reed) for Thursday
(April 14th)
Memory
Short-Term “Working” Memory
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 tobe-remembered items (words, characters,
digits)
Characteristics of STM
•
Limited Capacity
–
–
–
George Miller
Subject is given longer and longer lists of tobe-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
• Allan Baddeley:
Central
Executive
Articulatory
Loop
Visuospatial
Sketchpad
In general, how can we know if there are one,
two, or more independent systems handling
some aspect of perception or cognition?
A Modular Approach to STM
• Double-Dissociation: Indicates that two
processes or systems are independent
A Modular Approach to STM
• A dissociation occurs when one process is
influenced by changing a variable but
another process is not
A Modular Approach to STM
• A dissociation occurs when one process is
influenced by changing a variable but
another process is not
• A double-dissociation occurs when two
different processes are influenced by
changing two different variables
A Modular Approach to STM
Engine
Radio
Performance
Antenna
Sparkplugs
Damage
A Modular Approach to STM
• The logic of double-dissociation informs us
about working memory modules
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”
• result:
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)
Next Time:
• Long-Term Memory
• Read Loftus for Next Thursday