Presentation on theme: "Cognitive Psychology C81COG 5. Memory – Structure & Processes Dr Jonathan Stirk."— Presentation transcript:
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 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 ) EpisodicSemantic 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 Structure - Multi-store Model (Modal model) DECAY DISPLACEMENT INTERFERENCE Forgetting mechanisms Short- term store Long- term store Sensory registers (Atkinson & Shiffrin,1968)
Elaborative Rehearsal A strategy of associating a target stimulus with other information at the time of encoding I.e. Creating meaningful associations
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 Millers 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 task 1. 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 trigram 4. 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 1960s 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 LTM STM
Other factors effecting the serial-position curve: Word Frequency & STM 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 coding Confusions in recall between items which have similar sounds (Conrad, 1964; RLTKSJ RLCKSA) – Categorical but non-associative storage Meaningful 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 & Petersons (1959) expt! 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) seconds of a distracter task 3. Subject recalls the memory set (Prince…) 4. Next trial sometimes contains a homophone-related set e.g. MORNING, NOON, EVENING 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 Properties? So, is STM a pure system, with its own forgetting/coding characteristics, or does it share its properties with LTM? A qualitative difference from a quantitative change? – Oxidation of silver over time After 10 minutes (insensitive method) After 10 months (now more sensitive) The same process is at work, but the effects appear to be different over different time intervals Perhaps the methods of studying forgetting/coding are also insensitive and have also given misleading conclusions
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 & Tulvings Results As the depth of processing increases decisions take longer to make (latencies increase – red figures) and Unexpected recognition improves (blue bars) RED = latencies (secs)
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