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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Capacity

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

.1

.5

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

.1

.5

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