The modal model because of the huge influence it has had on memory research.
Structure
 Sensory
 Short-term
 Long-term
Processes
 Encoding: activities taking place during presentation of
information (study phase)
 Storage: activities taking place during the study-test interval
 Retrieval: activities taking place when stored information is
utilized (test phase)
▪ Failure to retrieve – forgetting

Purpose
 Passively registers input & briefly retains stimulus
trace after stimulus vanishes

Functions
 Helps us retain info that doesn’t last long
 Aids perception by allowing you to continue
processing after the stimulus is gone
 Keeps accurate record of stimulation so most
important can be processed further
STM
LTM

DURATION
< 30 sec
lifetime

CAPACITY
~7 chunks
unlimited

MAIN CODE
acousticarticulatory
semantic

RETRIEVAL

FORGETTING
serial
decay,
displacement
parallel
interference

Memory span
 the number of items that can be correctly recalled
in order (e.g., digit span test).

Miller (1956)
“The Magical Number Seven, Plus or Minus Two”
Limit of 7 + 2 chunks in STM
 Chunk: unit of info organized according to a rule
or some familiar pattern
 Chunk: collection of elements that are strongly
associated.
Task: immediate serial recall (“memory span”)
B V S M T A U I vs. T V U S A I B M
1492177619451963...
FB IJ FK FD RL BJ
• Capacity of STM: "about seven chunks”
Serial Position
21
19
17
15
13
11
9
7
5
3
1
Number of People Who
Recalled
100
80
60
40
20
0
Support for A & S model
 Two serial position effects
 Primacy Effect
 Better recall for words at beginning of list
 Recalled from LTM
 Recency Effect
 Better recall for words at end of list
 Recalled from STM
Support for A & S model
 Effect on serial position curve
 Speeding up presentation rate?
 Eliminate primacy effect
 Delaying the start of recall with an
interfering task?
 Eliminate recency effect
Primacy effect: better recall of first few words
Recency effect: better recall of last few words
P r o p o r t io n C o r r e c t
Glanzer & Cunitz (1966): delay between study and test
eliminates recency effect:
Task: free recall of word lists
0.8
No Distractor
0.6
30 Seconds
0.4
0.2
1
3
5
7
9
11
Serial Position
13
15
STM CAPACITY AND REHEARSAL TIME
One Syllable
Five Syllables
Sloth
Mumps
School
Greece
Switch
Math
Maine
Scroll
Zinc
Hippopotamus
Tuberculosis
University
Yugoslavia
Refrigerator
Physiology
Louisiana
Periodical
Aluminum
• Which list is faster to read aloud?
• Which list is harder to recall?
The word length effect
P r o p o r t io n C o r r e c t
Number of syllabes
1
mumps
2
measles
3
leprosy
4
diphteria
5
tuberculosis
Reading Rate
2.2 words/sec
2.0
“
1.7
“
1.5
“
1.3
“
Task: immediate serial recall of 6-item lists
1
0.8
0.6
0.4
1
2
3
4
Number of Syllabes
5
Acoustically similar lists: mad, plan, nap, bag….
Semantically similar lists: big, large, huge, great…
Control lists: pen, day, wish, bill….
TYPE OF SERIAL
RECALL TASK:
% words in correct
position
A
S
C
STM: 5 words,
one trial, no delay
.09
__% .64
__%
76%
LTM: 10 words,
four trials, delay
.70
__% .53
__%
72%
 Varied set of digits held in STM
E.g., memory set size of four: 2, 5, 8, 1
Task: is it in the set?
yes
no
R T (m s e c )
2
7
650
600
550
YES
500
NO
450
400
1
2
3
4
5
Size of Memory Set
Retrieval for STM: parallel or serial?
6

Conclusions:

STM duration:
 most info was gone after
about 18 seconds.

Why do we forget?
 Strong support for decay?
Percentage Recall
100
80
60
3 Words
40
20
3 Letters
0
0
2
4
6
8 10 12 14 16 18 20
Retention Interval
Lachman, Lachman, & Butterfield (1979)






Replicated the Peterson &
Peterson Task.
But, they also analyzed their data
by trial number.
1st trial is 1st word presented to
participants
Conclusion:
Forgetting almost does not occur
at the first trial,
But more forgetting with each
succeeding trial.
Why?
100
80
Percentage Recall

3 Second
Delay
60
40
18 Second
Delay
20
0
1
2
3
4
5
6
Trial Number
Adapted from Keppel & Underwood (1962)
•Things learned prior to study can proactively interfere
with memory STUDY phase.
R e c a ll P r o b a b ility
• Things learned between study and test can
retroactively interfere with memory TEST phase.
1
0.8
0.6
all trials
0.4
first trial
0.2
0
3
6
9
12
15
Recall Delay (sec)
18

Proactive Interference (PI) also occurs.

Proactive interference refers to forgetting
that occurs due to prior learning.
Current status
 Sensory memory is part of perception, rather
than memory
 Short-term memory is more flexible than just
a passive storehouse
 working memory

Parallel processing