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

DURATION < 30 sec lifetime

CAPACITY ~7 chunks unlimited

MAIN CODE acoustic- semantic

articulatory

RETRIEVAL serial parallel

FORGETTING decay, interferencedisplacement

STM LTM

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.

B V S M T A U I vs. T V U S A I B M

1 4 9 2 1 7 7 6 1 9 4 5 1 9 6 3 . . . F B I J F K F D R L B J

Task: immediate serial recall (“memory span”)

• Capacity of STM: "about seven chunks”

0

20

40

60

80

100

Serial Position

Nu

mb

er o

f Peo

ple

Wh

o

Rec

alle

d

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 modelEffect on serial position curve

Speeding up presentation rate? Eliminate primacy effect

Delaying the start of recall with an interfering task? Eliminate recency effect

Task: free recall of word lists

Primacy effect: better recall of first few wordsRecency effect: better recall of last few words

Glanzer & Cunitz (1966): delay between study and test eliminates recency effect:

0.2

0.4

0.6

0.8

Pro

po

rtio

n C

orre

ct

1 3 5 7 9 11 13 15

Serial Position

No Distractor

30 Seconds

One Syllable Five Syllables

Sloth HippopotamusMumps TuberculosisSchool UniversityGreece YugoslaviaSwitch RefrigeratorMath PhysiologyMaine LouisianaScroll PeriodicalZinc Aluminum

• Which list is faster to read aloud?

• Which list is harder to recall?

STM CAPACITY AND REHEARSAL TIME

0.4

0.6

0.8

1

Pro

po

rtio

n C

orre

ct

1 2 3 4 5

Number of Syllabes

Number of syllabes Reading Rate 1 mumps 2.2 words/sec 2 measles 2.0 “ 3 leprosy 1.7 “ 4 diphteria 1.5 “ 5 tuberculosis 1.3 “

Task: immediate serial recall of 6-item lists

The word length effect

% words in correctTYPE OF SERIAL positionRECALL TASK:

A S CSTM: 5 words,one trial, no delay __% __% 76%

LTM: 10 words,four trials, delay __% __% 72%

Acoustically similar lists: mad, plan, nap, bag….Semantically similar lists: big, large, huge, great…Control lists: pen, day, wish, bill….

.09

.70

.64

.53

Varied set of digits held in STM E.g., memory set size of four: 2, 5, 8, 1

Task: is it in the set?2 yes7 no

400

450

500

550

600

650

RT

(m

se

c)

1 2 3 4 5 6

Size of Memory Set

YES

NO

Retrieval for STM: parallel or serial?

Conclusions:

STM duration: most info was gone

after about 18 seconds.

Why do we forget? Strong support for

decay? Retention Interval

0 2 4 6 8 10 12 14 16 18 20

Per

cen

tage

Re

call

0

20

40

60

80

100

3 Words

3 Letters

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?

Trial Number

1 2 3 4 5 6

Per

cent

age

Rec

all

0

20

40

60

80

100

3 SecondDelay

18 SecondDelay

Adapted from Keppel & Underwood (1962)

•Things learned prior to study can proactively interfere with memory STUDY phase.

• Things learned between study and test can retroactively interfere with memory TEST phase.

0

0.2

0.4

0.6

0.8

1

Re

ca

ll P

ro

ba

bility

3 6 9 12 15 18

Recall Delay (sec)

all trials

first trial

Proactive Interference (PI) also occurs.

Proactive interference refers to forgetting that occurs due to prior learning.

Current statusSensory memory is part of

perception, rather than memoryShort-term memory is more flexible

than just a passive storehouse working memory

Parallel processing