Memory Short-term/Working Memory

Basic info-processing model of memory  Atkinson-Shiffrin 1968  The modal model Sensory Registry Short-Term Memory Long-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.) Proportion of correct recalls

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 ? 9 ?

Waugh & Norman 4 per sec. Condition ? 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 Proportion Correct Cond. 4 Cond. More about the number of items that interfered rather than decay over 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 1List 2 A - BA - C DOG - BALLDOG - WIRE Retroactive Later learning interferes with previously learned material A Proactive Prior 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 2 nd and 3 rd time  4 th 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.) Proportion Recalled 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   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