Overview of Memory
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Transcript of Overview of Memory
Overview of Memory
• Atkinson-Shiffrin Model
Sensory Signals
Sensory Memory
Short-Term Memory
Long-Term Memory
ATTENTION
REHEARSAL
RETRIEVAL
Sensory Memory
Supplementary reading:•Cognition (on reserve)
• Averbach and Sperling (course pack) Part 1
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
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F S F EG S A UT O C G
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Capacity
“Recall as many letters as you can”
Capacity
• George Sperling - Systematic investigation of memory capacity
– Result: subjects accurately recall about 4 items
– What can you conclude from this result?
– Maybe subjects can only hold about 4 items?
Capacity
• Could it be that subjects had encoded all the letters but failed to retrieve the information?
Capacity
• For example: What if they forgot the information before they could report it?– You would get the same result!
• 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
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Capacity
U E S BO D W AI B V S
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Capacity
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Capacity
Which Letters?
Capacity
• Partial Report
• Result: subjects can recall any 4 letters that are indicated by the arrow !
Capacity
• Partial Report
• Result: subjects can recall any 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
Probe Delay
# of letterspotentially recalled
500 ms0 ms never
0
4
10
Duration
• Partial Report
Delay
# of letters potentiallyrecalled
Interpretation:1. Information dwells in a brief storage “buffer”2. duration of storage lasts about 1/2 of one second
500 ms0 ms never
0
4
10
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 capacity3. pre-attentive
Properties of Sensory Memory
1. Brief (iconic ~500ms; echoic ~2 seconds)2. Virtually unlimited capacity3. pre-attentive
What happens if you attend to information in Sensory Memory?
Overview of Memory
• Atkinson-Shiffrin Model
Sensory Signals
Sensory Memory
Short-Term Memory
Long-Term Memory
ATTENTION
REHEARSAL
RETRIEVAL
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”
– Miller used the term “chunk” to refer to items in memory…
» But what is a “chunk”?
Capacity and Forgetting from STM
• Limited Capacity– Recalling takes time !
Capacity and Forgetting From STM
• Naveh-Benjamin & Ayers (1986)
• Showed that apparent span of STM is reduced for items that take longer to say
Capacity and Forgetting From STM• Brown (1958) and Peterson
& Peterson (1959)
• Subjects given list of “trigrams”
• Rehearsal prevented by counting backward by threes
• Showed that duration of STM is on the scale of seconds
Prop
ortio
n Co
rrec
t
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1.0
Delay (seconds)3 6 9 12 15 18
Capacity and Forgetting From STM• Rundus (1971)
• Long lists of “to-be-remembered” items
• Primacy Effect – participants more likely to recall first few items
• Recency Effect – participants more likely to recall last few items
Prob
abili
ty o
f Rec
all
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1.0
Position in list
2 6 10 14 18 24
Capacity and 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
Capacity and 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
Capacity and Forgetting from STM
• Interference in STM is complex and specific