2002/03/12psyc202-005, copyright jason harrison1 memory stores and memory processes what is your...

2002/03/12 Psyc202-005, Copyright Jason Harrison

1

Memory Stores and Memory Processes

What is your first memory?

2002/03/12 Psyc202-005, Copyright Jason Harrison 2

Technological metaphors

Plato: memory as an aviary, as a wax tabletMiddle ages: memory as a book, as an empty

cabinet1944: Our memories are card-indexes

consulted, and then put back in disorder by authorities whom we do not control (Cyril Connolly)

1950s: memory as a telephone system1960s: present: memory as a kind of computer


Memory

• Change blindness:– we don’t remember everything about a scene– but we do remember lots

• Stores: What types of memory do we have?

• Processes: How do these memory types work?


Memory Stores

• Sensory register/buffer– a “copy” of incoming stimulus– only lasts for a short time

• Short-Term Memory (STM)– a few important “chunks” or information– last as long as attention is given to it

• Long-Term Memory (LTM)– knowledge about the world (events,

experiences)– lasts indefinitely, infinite


Memory Processes

• Encoding – putting information into a store

• Maintenance – keeping it "alive”

• Retrieval– finding encoded information


Gradually fades away…

Incoming image Iconic image

Sensory Register: Iconic Memory

Immediately fades away…


a) show observer brief image (array of letters)

b) ask for a report of all remembered letters

a

b

h

j

k

tq

z

p

Sensory Register: Iconic Memory• How much can it store?

– Total-report technique


Total-Report Technique: results

• Observers can reliably report 4-5 items• Does this mean that only 4-5 items can

be stored?• No:

– May only mean that 4-5 items can be reported before items are forgotten.

– Response mechanism (attention?) takes time, iconic memory decays while reporting.

• How to test?


a) show observer brief image (array of letters)

c) ask for a report of letters in signaled row

b) signal one row via tone (high, medium, low)

Partial-Report Technique (Sperling)

a

b

h

j

k

tq

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p


Partial-Report Technique: Results• Observers can report 4-5 items from each

row– even when many rows were presented– (only one row selected by tone)

• Thus:– capacity of iconic memory is very high– elements fade rapidly, often before attention

can examine them– can only report 4-5 (before fading)


Summary of Sensory Registerdescription: a copy (photograph) of inputformat: copy of featurescapacity: very highentry of information: non-attentive

(automatic)duration: about 1/4 secondmaintenance of information: impossible


Short-Term MemoryWorking Memory• Store used for conscious tasks• Semantic not iconic• Lasts about 15 seconds• Constantly being written over• example: pail of water under a water tap:

– new stuff comes in (interference)– old stuff flows out (decay)


When light goes on (after several seconds) say what the consonants were

Test: briefly present subject with three consonants

GCH

Short-Term Memory (Working Memory)• is short term memory limited in size or

duration?


DurationAcc

ura

cy

100%

50%

0%30 s20 s10 s

Consonant Report Task: Results• Observers can report 3 consonants

– accurate as long as rehearsal possible– duration > 30 seconds (a long time!)


When light goes on (after several seconds) say what the consonants were

Briefly present subject with three consonants

KBS

Then have them count backwards by 3s out loud from given number

504

Decay of Short-Term Memory• information quickly decays when

rehearsal stops


Duration

Acc

ura

cy

100%

50%

0%30 s20 s10 s

Decay Task: Result• Performance declines rapidly with delay

– essentially zero after 15-20 seconds


Interference and Short-Term Memory• Present stimulus to be remembered• Present non-similar stimuli• Present similar “interfering” stimuli• Example:

– RHT, 520, 294, 93, BUMMER


3 digits: 2 7 3 100%

5 digits: 9 2 6 1 2 100%

7 digits: 4 6 7 8 1 0 4 90%

9 digits: 9 5 4 8 6 7 6 3 2 20%

Capacity of STM• Look at how recall depends on number of digits


Capacity of STM

• Number of digits recalled: digit span• Generically, capacity of STM: memory

span• Miller: memory span is 7(±2) items

– this is true for vision, audition, etc.– “the magical number 7”

• But.. 7 what?• What is an “item”• What are the units of STM?


For example, this sequence is difficult to remember:

FB IUB CIB MUN

But this sequence is easy to remember:

FBI UBC IBM UN

Second sequence has same letters - arranged as chunks - units have meaning

(11 letters)

(11 letters)

Units of STM: “Chunks”

• Chunk: group of items that have a meaning


Methods for Searching STM• Phone up movie theatre and listen to list

of movies currently playing• Answer the question:

– Are they playing A Beautiful Mind?

• To answer this question you could:– Parallel search– Serial, self-terminating search– Serial, exhaustive search

• Which one is most plausible? • What are the implications of each one?


Searching STM (Sternberg)

• Have subject remember 2 items in STM– e.g., W X– ask whether an item was in list (X?)– measure time taken to say “yes” or “no”

• Increase number of items to 3– e.g., A X U

• Repeat process for 4 items, 5 items, etc…• Look at time to say “yes” or “no” versus

number of items in memory


Average slope = 152 ms/ 4 items = 38 ms/item

Serial item-by-item scan of short-term memory

1 2 3 4 5Number of items held in STM

Reacti

on

tim

e (

ms)

400

500

600

-each item needs 38 ms to be checked

-scan is exhaustive - each item in STM checked

Search time of STM


Applications of STM

• Used for Many perceptual/cognitive tasks– tracking items across space– doing addition/subtraction– temporarily remembering phone numbers

• Specialized STM systems for vision, audition, spatial, faces, etc.

• Baddeley: general purpose “working memory” system


Spatial memory: Monkey vs. Human


CentralExecutive

Phonological Loop

Visuospatial Sketchpad

PL & VS are "slave" systems

Baddeley’s Model


Baddeley’s Model of WM (STM)

1. Auditory STM - “phonological loop”• allows maintenance/manipulation of speech-

based information (stink vs. sink vs. smell)• maintenance allows learning of new words

2. Visual STM - “Visuospatial sketchpad”• allows maintenance/manipulation of visual and

spatial information (shape, colour, position)• maintenance allows learning of new objects

3. Control System - “central executive”• selects which STM system to use• selects strategies for information manipulation


Summary of Short Term Memorydescription: data for mental operationsformat: “chunks”capacity: about 7 “chunks”entry of information: requires attentionduration: > 30 seconds (if not disturbed)maintenance of information: continued

attention and rehearsal required


Long Term Memory (LTM)• Separate system from STM• Evidence: damage to medial temporal

complex– HM (see Ramachandran)

hippocampus removed from both sides of brain– Patients with Korsakov’s syndrome

due to chronic alcoholism

• For these patients, long-term learning is impossible, but:– normal STM memory span– normal STM scanning speed


Capacity of LTM

• Essentially unlmited -- can always add more

• But, this does not mean that everything is available later…

• Recall different from Recognition


Recall versus Recognition

• Recall– What did your learn in class today?– need to generate facts, ideas

• Recognition– Did you learn about LTM in class today?– need to verify given facts, ideas

• Which is more difficult?


Conway, Cohen & Stanhope (1991)• Test what was learned in university classes

– recall of names and concepts– interval between 3 to 12 years

• How much of this kind of knowledge is remembered and for how long?

• Are some types of knowledge better remembered than others ?

• Does knowledge undergo structural changes over time?• Do older people forget faster than young people?• Is very long term retention superior when students originally

obtained high grades? • Do they remember it better if they found the material very

interesting when they studied it?


-memory for names decays sooner than for concepts

% c

orr

ect

reca

ll80

60

40

20

03 25 50 100 125

ConceptsNames

-both average to about 25% retention over long term

Results: Cued recall (fill in the blank)


Serial Position Effect (Rundus)

• Does recall accuracy depend on position in list?

• List of 20 nouns, one every 5 seconds– cat, ball, house, truck, pencil, vase, hose,

book, lake…

• Test recall as function of position• Two effects: primacy and recency


% c

orr

ect

reca

ll 80

60

40

20

01 5 10 15 20

Position

Primacy effect - better recall for words at beginning

Recency effect - better recall for words at end

Results: Serial Position Effect


Primacy and Recency Effects

• Primacy effect is due to…– greater rehearsal of items– more rehearsal, more chance to get into LTM– if rehearsal prevented, primacy effect

disappears

• Recency effect is due to… – items still in STM– if use of STM prevented (introduce another

task before testing) recency effect disappears


Types of LTM

• Most studies test for retention of words and concepts: semantic memory– general knowledge– not connected to any particular time or place– e.g.,

• meanings of words, • random facts about world• rules of multiplication

• What other type of memory is there?


Episodic Memory

• knowledge connected to a particular time or place

• not general – particular time or place or people

• e.g.,– dinner I ate yesterday– house I lived in when I was 10– what I did Sunday afternoon

• often autobiographical events


Semantic versus Episodic Memory• Semantic:

– who is the president of UBC?

• Episodic: – when did you first hear of Martha Piper?

• Amnesiacs generally more affected at level of episodic memory

• Episodic memory forms basis for mental imagery– generation of internal images (e.g., mom’s

face)


Mental Imagery

• Internal genration of “images”• Provides answers to questions about

particular things:– Where is the clock tower in relation to the

Main Library?

• Kosslyn– experiments on brain activity– imagery is vision “run backwards”


EyeObject

LGN

(visual cortex)

Geniculo-striate pathway

IT areas

Vision: forward process• input activates visual cortex (V1)• this activates higher centres


Eye (visual cortex)

Geniculo-striate pathway

IT areas

?

Imagery: backwards process• higher centres activate V1• activation of V1 gives “visual impression”• 5% of population cannot do this


Application of mental imageryRoman Room (“Method of Loci”)• used by Roman orators to memorize long speeches1. Pick a place you know well (e.g., your bedroom)2. Find a path to travel around the room3. Find items that suggest topics to be remembered

• e.g, hospital, doctor, cash

4. Place small-scale versions of these along path• according to order of speech

5. To recall, imagine walking around room• path helps you remember items• items help you remember topics


Improving LTM

• “Use it or lose it” – LTM doesn’t become stronger with use– But techniques you use do!

• To improve memory retention– More rehearsal (e.g., writing, review)

• increase probability of transfer to LTM

– More connections to existing knowledge• either semantic or episodic memories

– Sleep (8+ hours every night)• memory consolidation occurs during REM


Any other types of memory?

• Explicit memory– semantic– episodic

• Implicit memory– procedural– priming


Implicit Memory

• Memory formed without awareness– you didn’t try to remember it but you did

anyway– you didn’t try to recall it but you did anyway

• Two main types– procedural memory: how to do things– priming: bias towards recall based on cue


Procedural Memory: Notes• memory for actions, operations, skills, etc.

– e.g, how to tie shoelaces, ride a bike, start your car

• “automatic” but difficult to know how you do something:– can only start at particular points – memory not easily accessed consciously

• May involve “zombie”– procedural amnesia when striatum damaged

(part of midbrain near neocortex)– HM has procedural memory

(hippocampus removed; striatum intact)


From: www.mareshbrainsatwork.com/ B2B/SB10.html


Priming• Facilitation of a ability to recognize words,

images based on prior exposure• May not consciously remember prior

exposure• May not consciously see “prime”• Increase of 5-10% over non-primed stimuli• e.g.,

– prime with word -- show incomplete word -- ask for completions

– prime with named images -- show many more images -- ask for their names


Priming with words

c l o w n


Priming with words

c l o_ _

• Complete the word:


• cloak• clock• clods• clogs• clone• clonk• close

• cloth• clots• cloud• clout• clove• clown• cloys

Priming with words•Look at frequency of chosen words

•primed word chosen more often than chance•requires working neocortex


LTM

Explicit Implicit

Semantic Episodic Procedural Priming

Medial temporal complex Striatum Neocortex

Summary of LTM systems:

2002/03/12psyc202-005, copyright jason harrison1 memory stores and memory processes what is your...

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types of memory

capacity of iconic memory

iconic memory decays

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memory types work

decay slide