Overview of Memory
• Atkinson-Shiffrin Model
RETRIEVAL
ATTENTION
Sensory
Signals
Sensory
Memory
Short-Term
Memory
Long-Term
Memory
REHEARSAL
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
+
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 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
+
Capacity
U E S B
O D+W A
I B V S
Capacity
+
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
10
# of letters
potentially recalled
4
0
0 ms
500 ms
Probe Delay
never
Duration
• Partial Report
10
# of letters
potentially
recalled
4
0
0 ms
500 ms
never
Delay
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
Properties of Sensory Memory
1. Brief (iconic ~500ms; echoic ~2 seconds)
2. Virtually unlimited capacity
3. pre-attentive
What happens if you attend to information in Sensory Memory?
Overview of Memory
• Atkinson-Shiffrin Model
RETRIEVAL
ATTENTION
Sensory
Signals
Sensory
Memory
Short-Term
Memory
Long-Term
Memory
REHEARSAL
Characteristics of STM
•
Limited Capacity
– George Miller
– Subject is given longer and longer lists of to-beremembered 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
Proportion Correct
1.0
.5
.1
3
6
9
12 15 18
Delay (seconds)
Capacity and Forgetting From STM
• Rundus (1971)
• Primacy Effect –
participants more likely to
recall first few items
• Recency Effect –
participants more likely to
recall last few items
Probability of Recall
• Long lists of “to-beremembered” items
1.0
.5
.1
2
6
10
14
Position in list
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