Memory How does memory work?

The Modal Model 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 Partial report suggested 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

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 Paradigm “You will not be shocked during this experiment” Study unrelated information ‘T’ ‘K’ ‘B’ “wood” “dog” “candy” Count backward by 3’s Prevent rehearsal Vary duration of counting Recall studied items

Brown-Peterson Interval of counting (sec.) Decay 100 Proportion of correct recalls 1 18 Interval of counting (sec.) Decay (on average) memory information is accessible up to 18 seconds.

Decay Reconcilable with sensory memory Use it or lose it. Once memory is established, decay is constant What constitutes “established”? Is it always ~18sec.?

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 100 B-P Proportion Recalled .27 .44 Acoustic .35 .55 Semantic .52 .73 Reading Non-Exp Expect LOP Proportion of words recalled* Surprise Trials 1 18 Interval of counting (sec.) *They looked also at the strict scoring i.e. remembering the whole trigram, the pattern was the same but with poorer performance overall

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 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

Number of items between target & probe Waugh & Norman 100 Proportion Correct 1 Cond. 4 Cond. 1 13 Number of items between target & probe 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

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 Sebrechts 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 suggested there was more to short-term memory functioning than as a passive storage device

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

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 Central Executive Visuo-Spatial Sketchpad Phonological Loop Central Executive Coordinates the Slave Systems Response Selection Guides Attention Maintains visual and spatial information Maintains acoustic information

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

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.

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

Long-term memory Basically includes anything retained that did not occur few moments earlier Source of information that does not come from the environment

Learning Storage of information in memory as a consequence of experience Process of acquiring new associations among stimuli, responses and outcomes. What is Learned? How is it Learned? Associative theories Learning Cognitive theories Encoding and Retrieval

Classical Conditioning Characterized by the generalization of a fixed or previously learned behavior Responses are elicited from stimuli Unconditioned stimulus (US) Elicits a response without training Shock Unconditioned Response (UR) Elicited without training by a (US) Smacking whoever gave you the shock Conditioned Stimulus (CS) That which through training elicits a particular response Pretty flowers Conditioned Response (CR)* Response to the conditioned stimulus Smacking whoever gives you pretty flowers

Operant / Instrumental Conditioning Based on the principle of reinforcement What is reinforced? What is reinforcing? Development of associations between particular responses and consequences of the response (outcomes).

Basic Mechanisms of Operant Conditioning Behaviors have consequences Consequences are contingent on behaviors Organisms adapt behavior to match contingencies Consequences usually satisfy a “drive” Biological need Motivational need Well-being of individual

Consequences of Behavior Reinforcement or Punishment Reinforcement Consequences of behavior increase the probability of response (behavior) Punishment Consequences of behavior decreases the probability of response Both Reinforcement and Punishment can be positive or negative Positive: presentation of stimuli Negative: removal of stimuli The result is a table of contingencies…

Reinforcement and Punishment Response Increase (rein.) Decrease (pun.) Positive Reinforcement (reward) Positive Punishment (punishment) Apply a stimulus (+) Stimulus Negative Reinforcement Negative Punishment (omission) Remove a stimulus(-)

Associative Learning Accounts for certain types of memory phenomena Memory Structure Highly practiced information Habitual responses Stimulus generalization Assumes memory mechanism is the same as associative mechanism (single system)

Associative Memory Associative memory theory alone cannot account so well for other phenomena Free Recall No cue Subjective organization Von Restorff Effect Effect of stronger memory for a salient item in a series Sensory Memory “Direct” memory of sensory information Short-term representations No Practice Complexity of language acquisition/production Systematic memory distortions

Beyond association Although simple associative mechanisms described by classical and operant conditioning may account for some aspects of learning, more was needed Subtle shift from learning theories to theories of memory, which emphasized knowledge representation in an information processing system Focused on encoding and retrieval processes to help explain memory performance in a variety of settings Levels of Processing Encoding specificity Transfer appropriate processing

Basic Mechanisms of Memory Encoding Acquisition of Information “Learning” ? Maintenance Retaining information Retrieval Using information How do the processes of Encoding and Retrieval influence what is remembered?

Levels of Processing Craik & Lockhart (1972) Formalized the notion of “depth” of processing and demonstrated how it affects memory. There are “depths” to which information can be processed Shallow: encoding information in terms of its physical or sensory characteristics Deep: encoding information in terms of meaning Levels (for words) Structural Is it all caps? Shallow Phonetic Does it rhyme with _? Semantic Is it an animal? Deep

Proportion correctly recognized Levels of Processing 100 Proportion correctly recognized CAPS? Rhyme? Animal?

Levels of Processing Such results suggests that deeper levels of processing produce more permanent retention than shallow levels of processing. Distinctiveness and elaboration may be responsible for the effectiveness of deep levels of processing Other results Intention to learn does not change LOP pattern of results (Hyde & Jenkins, 1973) Generation effect (Slamecka and Graf, 1978) Self-reference task encourages especially deep levels of processing (Rogers, Kuiper, & Kirker 1977 Problem: What is “deep” and what is “shallow?” Circular logic If processing is deep then retention will be better. If retention was better, then processing must have been deeper. There is no precise way to measure ‘depth’

Encoding-Specificity Principle Information is available to the extent to which retrieval cue matches encoding Tulving and Thomson, (1973)

Morris, Bransford, & Franks (1977) Had people make one of two judgments at presentation Shallow: Rhyming (Does it rhyme with hat?) Deep: Semantic (Does it have a tail?) Two test conditions Recognition Rhyming “Hat” “Did you see a word that rhymes with X?” Test Condition either matched or mismatched original encoding

Morris, Bransford, & Franks Rhyme Semantic Recognition TEST PRESENTATION + -

Morris, Bransford, & Franks LOP effect for standard test. But opposite for rhyming test Deep processing does not always enhance memory

Transfer Appropriate Processing Memory performance depends on the extent to which processes used at the time of learning are the same as those used when memory is tested LOP approach assumed that semantic processing was always superior to non-semantic processing The transfer appropriate processing approach demonstrates that a form of encoding which is “shallow” for one purpose might be “deep” for another. Conclusion Memory not just a function of depth of processing Depends also on the match between encoding processes and type of test

Interaction of Encoding and Retrieval Context Congruency Godden & Baddeley Divers memorized a list of words Half learned the words on dry land Half learned words underwater Tested either on dry land or underwater

Recap LEVELS OF PROCESSING emphasizes operations at encoding semantic/elaborative processing better for LTM ENCODING SPECIFICITY emphasizes that information about retrieval cue must be encoded at study for cue to be effective TRANSFER APPROPRIATE PROCESSING memory best when processes at test match processes used at study *For another view, see Nairne, 2002

Different Methods of Retrieval What is your name? Automatic What is the Capital of Australia? Generate & recognize What are you doing next Tuesday at 1200? Schema + Search What is the layout of your house? Spatial Is “FLORB” a word? Direct access What was Beethoven’s telephone number? General knowledge search

Basic Mechanisms General Principles of Memory Strength Congruity Background Contextual Congruity Between encoding and retrieval Organization Distinctiveness Segregate item in memory Spacing Massed vs. Distributed Recency and Primacy

Spacing Old rule: Spacing learning enhances recall Bahrick family and foreign language learning 

Spacing Why does it work? Varying encodings may lead to more associations Reminds of earlier presentation, so may reinforce earlier learning (perhaps increasing baseline activation)

Recency and Primacy Demonstrated in the serial-position curve Learn a list of items in order… ..and reproduce the list in order Position in List Proportion Recalled 100 Beg. Mid. End

Recency and Primacy Primacy Recency Memory advantage for items initially encountered. Rehearsal? Distinctiveness? Recency Memory advantage for items recently encountered. Working memory?

Retrieval Many different theories about how retrieval takes place. Information Processing Theories Modal Model, LOP, TAP Associative Theories ACT-R, TODAM Search Models SAM, REM Trace Theories Perturbation Model Connectionist Models PDP, EPIC Biological-Based Theories HERA, CARA Differ… What and how information is retrieved. Memory trace Reconstruction Share… Emphasis on information available at retrieval Cues Contextual information Something guides retrieval Memory as a Decision