Transcript 2320Lecture23

Upcoming Reading
•False Memories (Beth Loftus)
•Lost Mariner (Oliver Sacks)
Extra Reading
•Cognition on reserve in Library
Overview of Memory
RETRIEVAL
• Atkinson-Shiffrin Model
ATTENTION
Sensory
Signals
Sensory
Memory
Short-Term
Memory
Long-Term
Memory
REHEARSAL
“Types” of Memory
• Sensory Memory
– brief ( < 1 second)
– preattentive / parallel processing (very
large capacity)
Sensory Memory
Capacity
• Describe a simple experiment that could
measure the capacity of “memory”
Capacity
• Describe a simple experiment that could
measure the capacity of “memory”
• Briefly present some letters or digits and
then ask the subject to report them
– Called “whole report”
Capacity
+
Capacity
F S F E
G S+ A U
T O C G
Capacity
“Recall as many letters as you can”
Capacity
• George Sperling - Systematic investigation
of memory capacity
– Result: subjects accurately recall 3 or 4 items
– What can you conclude from this result?
Capacity
• Could it be that subjects had encoded but
failed to retrieve the information?
Capacity
• For example: what if recalling interferes
with memory?
• How could you modify the experiment to
measure the instantaneous capacity, before
any forgetting can occur?
Capacity
• Partial Report - briefly present letters or
digits and ask subject to report only some of
them
“Report the letters in the row
indicated by the arrow”
Capacity
+
Capacity
U E S B
O D+W A
I B V S
Capacity
+
Capacity
+
Capacity
Which Letters?
Capacity
• Partial Report
• Result: subjects can recall any 3 or 4 letters
that are indicated by the arrow !
Capacity
• Partial Report
• Result: subjects can recall any 3 or 4 letters
that are indicated by the arrow !
• What does this mean about the capacity of
memory?
Capacity
• There is some part of the perception system
that stores huge amounts of information…
– in fact, if only a single letter is probed,
instantaneous capacity is seen to be unlimited
Duration
• There is some part of the perception system
that stores huge amounts of information…
• But for how long? How would you design
an experiment to measure the duration of
this high-capacity memory system?
Duration
• There is some part of the perception system
that stores huge amounts of information…
• But for how long? How would you design
an experiment to measure the duration of
this high-capacity memory system?
• Vary the onset of the probe
Duration
• Partial Report
# of letters
potentially
recalled
10
4
0
0 ms
500 ms
never
Probe Delay
Duration
• Partial Report
10
# of letters
potentially 4
recalled
0
0 ms
500 ms
Delay
never
Interpretation:
1. Information dwells in a brief storage “buffer”
2. duration of storage lasts about 1/2 of one second
Iconic Memory
• a brief storage of “raw data” in the visual
system
Echoic Memory
• Auditory information is stored in a similar
sensory “buffer”
– Echoic memory seems to last for several
seconds
Properties of Sensory Memory
1. Brief (iconic ~500ms; echoic ~2 seconds)
Properties of Sensory Memory
1. Brief (iconic ~500ms; echoic ~2 seconds)
2. Virtually unlimited capacity
Properties of Sensory Memory
1. Brief (iconic ~500ms; echoic ~2 seconds)
2. Virtually unlimited capacity
3. pre-attentive
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
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)