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Cognitive Psychology C81COG 5. Memory – Structure & Processes. Dr Jonathan Stirk. Background Reading. Baddeley, A.D. (1999). Essentials of human memory. Hove, UK: Psychology Press. Chapters 2 & 3. Overview. Dichotomies in the description of memory Memory Processes - PowerPoint PPT Presentation
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Cognitive Psychology C81COG5. Memory – Structure & Processes
Dr Jonathan Stirk
Background Reading
Baddeley, A.D. (1999). Essentials of human memory. Hove, UK: Psychology Press.– Chapters 2 & 3
Overview
Dichotomies in the description of memory Memory Processes Structural attempts to separate STM and LTM
– forgetting by decay or interference – capacity differences – coding by sounds or by meanings?
The simple multi-store model fails, so– an alternative to structural distinctions?– a revised model, based upon “working
memory”
Common distinctions in the description of memory
Short-term (1°) vs. Long-term memory (2°)– The phone number of your dentist (look it up in the
phone book, then dial it) vs.– A very familiar phone number (e.g. Home)– Distinction based on temporal aspects of memory
Temporary and fleeting vs. more permanent and stable
Common distinctions in the description of memory
MEMORY(LTM)
Procedural [non-declarative]
(Skills, priming, conditioning)
Episodic Semantic
Declarative(Knowledge)
Open to intentional retrieval
Larry Squire (1992)
Measured through performance rather than conscious
recall/recognition
Procedural vs. Declarative LTM
How to tie your shoelaces vs. the name of the current US president
How? That?
Episodic vs. Semantic LTM
What did you have for lunch today? vs. What kinds of animals are canaries?
Semantic Memory – Tulving (1972)
“It is a mental thesaurus, organised knowledge a person possesses about words and other verbal symbols, their meanings and referents, about relations among them, and about rules, formulas, and algorithms for the manipulation of these symbols, concepts, and relations.”
Memory Processes
Memory Structure - Multi-store Model (Modal model)
DECAY DISPLACEMENT INTERFERENCEForgetting mechanisms
Short-term store
Long-term store
Sensory
registers
(Atkinson & Shiffrin,1968)
Differences Between Memory Stores
Evidence for separate and distinct memory stores has been supported by looking at:– Forgetting mechanism(s)– Storage capacity– Temporal duration– Effects of brain damage
Properties Of The Short Term Store
FORGETTING MECHANISMS– Loss of information through autonomous decay – Distraction results in loss of information (Peterson &
Peterson, 1959)
LIMITED STORAGE CAPACITY – STM span limited to 3 items (pure STM capacity limit;
not Miller’s 7+-2; see next slide)– Recency in serial recall curve is read-out from Primary
Memory (Craik, 1964) – Delayed recall eliminates recency (Glanzer & Cunitz,
1966)
Chunking Allows More Information To Be Stored
Miller (1956) suggested that memory capacity is not limited by number of items that can be stored but by number of chunks. Chunking requires support by LTM
Evidence for forgetting by decay in a STM task
Peterson & Peterson (1959) distracter task1. Listen to a consonant trigram (e.g. SKB)2. Now start counting backwards in threes from
this number (e.g. 751)– Varied how long they did this for (variable
delay to allow the counting to have an effect)3. Now recall the trigram4. Repeat 1-3 for more trials/trigrams
Q. What % of trigrams are correctly recalled, and how is this influenced by the delay between presentation and recall?
Loss Of Information From STM By Decay
Delay between presentation of trigram & recall, during which participants are distracted by counting backwards, & during which forgetting is possible
Interpretation: We lose information from STM through autonomous decay when information is left unattended.Around the 1960’s forgetting in LTM was thought to be by interference
See also Brown (1958)•Also known as Brown-
Peterson distracter task
Results
Glanzer & Cunitz (1966) – Further evidence of 2 stores (STS & LTS)
Primacy Effect
Usual recency effect (about 3
items!)
Recency effect is
eliminated by delay
LTMSTM
Other factors effecting the serial-position curve: Word Frequency & STM
00.10.20.30.40.50.60.70.80.9
1
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Serial (List) Position
Pro
por
tion
Cor
rect high freq
(common)
low freq (rare)
LTM STM
Raymond, 1969
Double Dissociation
The primacy effect is altered by– The word frequency of
items used in the task Low frequency words
→ lower recall of first few items in list
The recency effect is altered by – the use of a delay
between learning & recall
distracter task → lower recall of last items in list
Double Dissociation: two situations or theoretical entities are affected in opposite ways by one or more independent variables
But NOT by a delay! But NOT by word frequency!
Recall These 8 Letters In Order
1. V C B D G E P T
2. R F Q P L N Z K
Recall These 8 Letters In Order
1. V C B D G E P T
2. R F Q P L N Z K
Did you perform better for list 2?
Further Properties Of The Short Term Store
Coding Coding in LTM is thought to be semantic (based
on meaning)/associative. What about coding in STM then?
– Evidence for Acoustic codingConfusions in recall between items which
have similar sounds (Conrad, 1964; RLTKSJ →RLCKSA)
– Categorical but non-associative storageMeaningful relationships between words
are not appreciated (Tulving & Patterson, 1968; )
Summary of Properties Of STM
The short-term store retains a limited amount of information for a brief interval, and what it retains is categorical but non-associative items using an acoustic code– Limited capacity– Short duration (information lost by decay if
not rehearsed)– Phonologically coded
Problems With Earlier Interpretation of Peterson & Peterson’s (1959) exp’t!
Keppel & Underwood (1962) An average taken for each subject across numerous trials This assumes no performance change across trials
After an 18 sec delay, PI from triplets presented on earlier trials builds up.
Pro-active interference/inhibition (interference from info presented before the to be remembered info)
No forgetting on trial 1, some on 2, more on 3
Problem: Evidence of Semantic Coding In a STM task
Warren & Warren (1976)
1. S hears PRINCE, KNIGHT, QUEEN (the “memory set”)2. 10 seconds of a distracter task3. Subject recalls the “memory set” (“Prince…”)4. Next trial sometimes contains a homophone-related set
e.g. MORNING, NOON, EVENING5. 10 seconds of distraction, etc, etc
Question - Do subjects ever confuse KNIGHT and NIGHT in the recall of the homophone-related set? (Is night offered in error in the recall of MORNING, NOON, EVENING?)
Answer - YES, therefore there has been some semantic processing of these words even though they are in a STM task
Separate Stores?
So evidence for 2 separate stores is not conclusive!
Rather than focusing on structure, why not look at the processing of information instead?– Craik & Tulving (1975)
Levels Of Processing Approach (Craik & Tulving, 1975)
Structural model breaks down– Atkinson & Shiffrin (1968)
Rehearsal always enhances transfer to LTM Not true!
Remembering is influenced by the “level of processing” during input (e.g. visual processing vs. semantic processing)
The emphasis is now upon process rather than structure
Craik & Lockhart (1972)- Levels of processing hypothesis
Depth of processing predicts durability of memory
Craig & Tulving (1975) - List of visually presented, unrelated words.
3 groups each with a different decision task – 1. Is the word in CAPITALS? – 2. Does it rhyme with “ate"?– 3. Is it a type of fish? Or does the word fit into the
following sentence? Measured latency (decision time) Then surprise memory test – recognition from
list of targets & distracters
Craik & Tulving’s Results
As the depth of processing increases decisions take longer to make (latencies increase – red figures)
and Unexpected
recognition improves (blue bars)
0.614
RED = latencies (secs)
0.689
0.746
Updating The Multi-store Model Of Memory
Baddeley & Hitch (1974) Model emphasises both storage AND processing Not unitary – verbal /visual-spatial subsystems Original incarnation was tripartite (3 components)
Working Memory
Central executive: directs and controls all WM functions; can be thought of as ‘attention’. Integrates info
Visuospatial scratchpad/sketchpad: a system for holding visual information
Articulatory/phonological loop: a system for holding and recycling auditory/acoustic information– Rehearsal/Articulatory loop : a process for recycling,
using subvocalization– Phonological buffer/store: a structure for holding acoustic
information
Working Memory Updates
Later version (Baddeley, 2000) incorporate an “episodic buffer” which time-stamps memories– So we know when something happened and not
just that it happened Later versions split the articulatory loop and
visuo-spatial sketch pad into two dual slave systems which are used by the CE