Memory

Short-term/Working Memory

Basic info-processing model of memory Atkinson-Shiffrin 1968 The modal model

Sensory RegistryShort-Term

MemoryLong-Term

Memory

Attention Rehearsal

Sensory Memory

Recall Sperling

Participants view a briefly presented array of letters.

Tone cued participants to recall items. Change the duration between

presentation of array and the recall tone

Sperling

Full-report paradigm Report as many items as possible Recall (no delay) = 3-4 items Recall decreased with short delay

Partial-report paradigm Tone cued which line of the array to recall

High = top line Medium = middle line Low = bottom line

Compare recall across rows

Partial-report paradigm

Recall with no delay roughly ~3 regardless of row

Same pattern of results with tone delay All information gets in Lasts a short time Sensory memory is rather large but has a

short duration

Short-term memory

The theory of STM was brought about during the cognitive revolution and is a product of the information processing perspective

It proposed that attended information went into an intermediate short-term memory where it had to be rehearsed (processed) before it could go into a relatively permanent long-term memory.

STM is biased toward keeping recent information available and has a limited capacity to do so. Memory span - the number of elements one can

immediately repeat back

Short-term memory

In a study of memory span, participants might rehearse digits by saying them over and over again to themselves.

With each rehearsal of an item, it was assumed there was a probability that the information would be transferred to a relatively permanent long-term memory.

If the item left short-term memory before a permanent long-term memory representation was developed, however, it would be lost forever.

One could not keep information in short-term memory indefinitely because new information would always be coming in and pushing out old information from the limited short-term memory.

One of the questions with STM regarded its duration

What determines the duration of STM? Decay?

Gradual loss of memory “strength” over time. Interference?

Access to information is blocked by the retrieval of other information

Overwriting? Original memory trace is altered

Decay

Brown-Peterson Task Use unrelated information

‘T’ ‘K’ ‘B’ “wood” “dog” “candy”

Many study-test trials “You will not be shocked in this experiment”

Paradigm Study three items Count backward by 3’s

Prevent rehearsal Vary duration of counting Recall studied items

Brown-Peterson

Decay (on average) memory information is

accessible up to 18 seconds.

Interval of counting (sec.)

Pro

port

ion

of c

orre

ct r

ecal

ls

0

100

1 18

Decay

Reconcilable with sensory memory Use it or lose it.

Once memory is established, decay is constant

What constitutes “established?” Is it always 18sec.?

Interference

Memory is more active Newly encountered information (if

used) limits the access to previous information.

Interference is often confounded with “decay”

Interference

Waugh & Norman (1965) Present a set of 16 digits at a fixed interval.

1 digit per second 4 digits per second

Last digit in the set served as a probe, and had previously been presented once

Report the digit that appeared after the probe digit had appeared in the list the first time (target).

Manipulate the number of digits that appear between target and the probe. Retention interval

Waugh & Norman

1 per sec. Condition

1597? 9 ?

Waugh & Norman

4 per sec. Condition

1323574895467318? 9 ?

Waugh & Norman

If forgetting is a function of decay (time) then there should be less recall for slower rate (16 secs) vs. faster rate (4 secs)

If interference then should be little to no difference between the two.

Waugh & Norman

Number of items between target & probe

Pro

port

ion

Cor

rect

0

100

1 13

1 Cond.4 Cond.

More about the number of items that interfered rather than decayover time

Interference

So the Waugh and Norman results suggest interference from additional information can disrupt memory for particular items

Two types of interference Retroactive Interference

New information interferes with previously learned information

Proactive Interference Previously learned information interferes with the

acquisition of new information

Retroactive Interference & Proactive Interference

Two-list paradigm Paired associates Two items paired with same target

across lists Probe with target

Retroactive Interference & Proactive Interference

List 1 List 2A - B A - C

DOG - BALL DOG - WIRE

RetroactiveLater learning interferes with previously learned material A

ProactivePrior learning interferes with material learned later

???B (ball)

C (wire)

Release from PI (Wickens, 1972)

Design Given three items of a

particular category Countdown Recall Repeat with new

category exemplars a 2nd and 3rd time

4th time repeat or give three from a new category

Recall goes back to original levels with new category

Very Rapid Forgetting Sebrechts, Marsh, & Seamon (1989) based on

Muter (1980) Used a modified Brown-Peterson paradigm with

false trials. B-P task

Acoustic (shallow) Long E sound?

Semantic Is it animate?

Reading say the stimuli aloud

Exp 1 regular B-P experiment Exp 2 “Surprise” memory test

Sebrechts, Marsh, Seamon

Ss presented words sequentially and made a yes/no decision for each word presented or just read aloud depending on condition

Countdown followed

Brown-Peterson trial

WOOD KEY TIME

382

Recall

Sebrechts, Marsh, & Seamon

Forgetting within 6 seconds Expectation of retrieval is

necessary to maintain information in memory, but also elaboration can have an effect

So again the idea of decay doesn’t provide for the whole story

.27.44Acoustic

.35.55Semantic

.52.73Reading

Non-ExpExpectLOP

Proportion of words recalled*

Interval of counting (sec.)

Prop

orti

on R

ecal

led

0

100

1 18

B-P

Surprise Trials

*They looked also at the strict scoring i.e. remembering the whole trigram, the pattern was the same but with poorer performance overall

Interference

A possible explanation for interference is that when given cue, information associated with cue interferes with other info also associated with cue More items a cue is stored with the less effective it will be

in retrieving any one particular item Recall fan effect

But along with interference as another possible explanation of forgetting, the Sebrects et al., shows other factors will have a say in how forgetting occurs Expectancy ‘Depth’ of encoding

The decline of STM

The idea of a short-term passive ‘store’ fit in with the current information processing models Rapid forgetting

Transient nature suggests different type of store

Amount of rehearsal controlled the amount transferred to LTM More rehearsal more remembering Info had to ‘do time’ before getting to LTM

The decline of STM

Problems Loss similar for better learned material (initial rapid loss followed by

slower loss later) Rehearsal by itself won’t determine what makes it to LTM: Chunking

7 + 2 What may be chunked and how chunking occurs can depend on a

variety of factors and varies across individuals Depth of processing (Craik & Lockhart, 1972)

The Sebrechts article was an example of how DoP had a role even if there was decay

Some experiences gain immediate access to LTM E.g. traumatic events

Such findings suggest there is more to short-term memory functioning than as a passive storage device until information makes it to LTM through rehearsal or just goes away

Working Memory Function = short-term retention and manipulation of

information. Active memory Issues regarding working memory

How long? How much? What type?

Capacity Forgetting curve (Brown-Peterson) Miller’s 7 +/- 2

Capacity

Measured by span The number of items reproducible over a short

interval. Incrementally add items to a memory set.

Span varies … Among individuals

Individual Differences Across types of information

Rhyming > Non-rhyming Digits > Words Pictures > Labels

Baddeley

Model of WM Based on perceptual codes

Acoustic Visual and Spatial

Information can be retained separate from its use for a short time

Coordinating process guides the use of retained information

Central Executive “Slave” systems

“Rehearse” information for a short time Perceptually based

Baddeley’s Model of WM

Maintains visual and

spatial information

Maintains acoustic

information

Central executive

Coordinates the Slave Systems

Response Selection

Guides Attention

Visuo-Spatial

Sketchpad

Phonological

Loop

Central Executive

Baddeley’s Model of WM

Brown-Peterson Task CE attends to memory

set elements CE “stores” memory

set in phonological loop PL attempts to

rehearse the memory set during distraction

CE involved in distractor task (calculation)

CE coordinates retrieval from PL during recall

Visuo-Spatial

Sketchpad

Phonological

Loop

Central Executive

Phonological Loop

Two components Phonological store Articulatory control process

Subvocal articulatory rehearsal Traces within the store decay over a period of about two

seconds unless refreshed by rehearsal, a process akin to subvocalization and one that is dependent on the second component, the articulatory system

Important for long-term phonological learning e.g., language learning

Some evidence for the loop

Phonological similarity effect PGTVCD vs. RHXKWY Similar phono code leads to confusion

Irrelevant speech effect Colle & Welsh (1976): even a foreign language can interfere with

immediate recall of items Because of the nature of the code, the language gains access to

the phono store Articulatory suppression

Operation of the loop is disturbed if overt or cover articulation takes place

Vocalization utilizes same system as subvocal rehearsal, and hence can lead to difficulty learning verbal information

Word length effect

Word-length Effect Span decreases as the length of a word increases Less can be rehearsed within the ~2 sec time frame

ASSOCIATION

PARLIAMENT

CONCENTRATION

EMPOWERMENT

DOG

HOUSE

BAT

GLASS

WOOD

BIKE

Visuo-spatial Sketchpad

Temporarily maintains and manipulates visuospatial information

Plays an important role in spatial orientation and in the solution of visuospatial problems Both visual (imagery) and spatial

component Possibly two different systems

Some evidence for the sketchpad

Baddeley & Lieberman (1980) Visual tracking

interferes with imagery mneumonic

Irrelevant picture effect Same result even from

just looking at visual stimuli

Central Executive

Most complex and least understood component of WM

Model suggests CE coordinates the activity of the two slave systems

Other potential roles Coordinating retrieval strategies Selective attention Suppression of habitual responses Task switching Temporary activation of long term memory Binding of sensory and conceptual information

Assumptions and Predictions

Slave systems are independent of each other It is possible to do a both a verbal task and a spatial task at the

same time Extremely difficult to do two verbal (or two spatial) tasks at the

same time. Dual-Task Paradigm

Participant must perform more than one task at a time Slave systems have limited capacity

Span Slave systems can function autonomously from the Central

Executive Can do “Central Executive tasks” and slave system tasks at the

same time Central Executive coordinates information based on current

goals Implies intentional (conscious) control of WM Coordination involves many processes.

Questions regarding the WM model

Articulatory suppression: AS should prevent registration of visual material

(which must be recoded phonologically) In fact, span only drops slightly How is this material stored?

Chunking: Presumably info in LTM is used to chunk How is this information integrated?

Rehearsal Does rehearsal have to be subvocal? How are items in VS rehearsed? What about children? (they do not spontaneously

rehearse subvocally)

The role of consciousness CE originally proposed to assist in binding - our ability to

integrate information about location, color, size, smell, feel etc of objects.

How could it do this without a multimodal short term store?

Questions regarding the WM model

The Episodic Buffer

“A limited capacity temporary storage system that is capable of integrating information from a variety of sources”

Controlled by the CE

Feeds information into and retrieves information from LTM

Uses a common “multidimensional” code

The Episodic Buffer makes the link between Working Memory and LTM more explicit

Working Memory today