Download Chapter 7 (Memory).

Chapter 7
Semantic memory: Memory for general information
Episodic memory: Memory for personal events
There are three main systems in memory:
Encoding: Forming a memory code, which usually requires attention
Storage: Maintaining encoded information in memory over time
Retrieval: Recovering information from memory stores
Forgetting may be due to deficiencies in any of these three key processes
Encoding: Getting Information into Memory (p. 284)
Forgetting someone's name after meeting them is a failure to form a memory code for their name you're too busy thinking about what you're going to say to properly encode the information
The "next-in-line effect" shows that subjects tend not to recall much of what is said if their turn to speak
is coming - they are too preoccupied rehearsing to pay attention to what is being said
The Role of Attention
Attention: Focusing awareness on a narrowed range of stimuli or events - this is like a filter, allowing
only a select few things to pass into conscious awareness
This screening process may occur early in information processing - during input - or late - after the brain
has processed the meaning of the input
The "cocktail party phenomenon" suggests it's the latter - if someone in another conversation mentions
your name, you may notice, even though you have been ignoring the conversation, so some of it must
have been processed
There is also evidence for early attention, leading some to suggest that the attention filter is not fixed its position depends on the amount of information being processed
When attending to complicated tasks that consume much of our attention, selection tends to occur
early - when we are involved in simpler tasks, more attentional capacity is left over to process the
meaning of distractions
When participants are forced to divide their attention between memory encoding and some other task,
large reductions in memory performance are seen - for example, after hearing your name in a nearby
conversation, it's hard to follow two conversations at once
Research suggests that the brain can only handle one attention consuming task at a time - when people
multitask, they are really just switching their attention back and forth among tasks, rather than
processing them simultaneously
While most information fits this pattern of effortful processing, some types of information can be
acquired automatically - people are surprisingly accurate at answering questions about things like word
frequency without trying to remember it
Levels of processing
Depending on which aspects of stimuli you focus on, information will be encoded differently - this is one
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Depending on which aspects of stimuli you focus on, information will be encoded differently - this is one
of the main factors influencing memory, with rates of forgetting based on different methods of encoding
In dealing with verbal information, there are three progressively deeper levels of processing: structural,
phonemic, and semantic
Structural encoding: Shallow processing that emphasizes the physical structure of the stimulus
Phonemic encoding: Emphasizes what a word sounds like
Semantic encoding: Emphasizes the meaning of verbal input, thinking about the objects and actions
represented
Levels-of-processing theory: Proposes that deeper levels of processing result in longer-lasting memory
codes - research shows that recall is low after structural encoding, and highest after semantic encoding
Enriching Encoding
Elaboration: Linking a stimulus to other information at the time of encoding - the additional associations
created by elaboration help people to remember information, and this usually involves thinking of
examples to illustrate an idea
- For example, learning about classical conditioning, you may think about your fear of spiders,
helping you remember the concepts
Visual imagery: Representing words to be remembered as a mental image can enrich encoding, though
some words are easier to create images for than others
- Dual-encoding theory: Holds that memory is enhanced by forming semantic and visual codes,
since either can lead to recall - the memory is encoded twice
Self-referent encoding: Deciding how or whether information is personally relevant - self-referent
encoding can lead to improved recall, additional elaboration, and better organization
Storage: Maintaining Information in Memory (p. 289)
Information processing theories have subdivided memory into three separate memory stores - sensory
memory, short-term memory, and long-term memory
Sensory memory
Sensory memory: Preserves information in its original sensory form for a brief period of time, usually
only a fraction of a second - this allows the sensation of a visual pattern, sound, or touch to linger for a
brief moment
When it comes to vision, we perceive an afterimage rather than the image itself - for example, the trail
behind a sparkler
These brief preservations of sensation give you additional time to recognize the stimuli - but they are
very brief, as memory traces in vision last for 1/4 of a second and less than a second for hearing
Short-term memory
Short-term memory (STM): A limited-capacity store that can hold unrehearsed information for up to 20
seconds - can hold 5-9 pieces of information
Rehearsal: The process of repetitively verbalizing or thinking about information
- Maintenance rehearsal: Maintains the information in your consciousness (no real encoding into
long-term memory - just attempted memorization) - repeating a phone number is an example of
this
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this
- Maintenance rehearsal could, in theory, help you remember something indefinitely, but in
practice you're eventually distracted, and you'll forget if you rely only on maintenance rehearsal
- Elaborative rehearsal: Rehearsing with deeper levels or processing (focusing on meaning of words
to be remembered, for example) to increase the probability information will be retained - studying
is an example of this
Interference as well as time decay affect retention in short-term memory - after about fifteen seconds,
retention tends to be poor, but giving additional information can make subjects lose prior information
The average number of items that can be held in short-term memory is seven - it ranges from 5 to 9,
making seven the "magic number" and the actual capacity being "seven plus or minus two"
The capacity of short-term memory constrains the ability to mentally juggle various pieces of
information
Chunking: A short-term memory strategy where information is broken up into chunks, groups of familiar
or similar stimuli stored as a single unit - rather than attempting to remember each part separately, you
remember the larger groups
- While "I" "B" and "M" are three letters, and should take up three spaces in short-term memory, if
you simply have to remember "IBM" it doesn't take as much effort
- However, you would have to recognize IBM as a familiar unit, which is stored somewhere in longterm memory - so the long-term memory spills over to help out the short-term memory
- One primary difference between experts and beginners in a domain is how they process
information - beginners at chess have difficulty remembering the locations of pieces on a board,
while experts will "chunk" the locations together into meaningful patterns and be more likely to
retain the positions
Short-term memory as "Working Memory"
Previous research believed that short-term memory was limited to phonemic encoding, nor is decay
over time the only process responsible for loss of information
A new model of short-term memory was created, characterizing it as "working memory" with four
different components:
- Phonological loop: The short-term memory modelled previously - recitation and rehearsal,
phonemic encoding, etc. The maintenance rehearsal loop is termed Baddeley's Loop
- Visuospatial sketchpad: Permits people to temporarily hold and manipulate visual images - for
example, mentally re-arranging furniture in your room
- Central executive system: Controls the deployment of attention, switching the focus of attention
and dividing attention as needed - co-ordinates the actions of the other components
- Episodic buffer: Temporary, limited-capacity store that allows the various components of working
memory to integrate information, which serves as an interface between working memory and
long-term memory
The separate modules work somewhat independently - visual processing tasks using the visuospatial
sketchpad do not interfere with verbal processing tasks using the phonological loop
Variations in working memory capacity correlate positively with measures of high-level cognitive abilities
such as reading comprehension and flexibility in attention
Long-term memory
Long-term memory (LTM): Unlimited capacity store that can hold information over lengthy periods of
time - perhaps even indefinitely
One view of long-term memory is that it is permanent, and failure to remember comes from a failure in
retrieval, not storage - though this view is disputed
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Electrical stimulation of the brain can apparently recreate vivid descriptions of long-lost memories seemingly exact playbacks
- However, the memories unearthed by electrical stimulation of the brain were actually filled with
major distortions or factual impossibilities - it seems they were actually hallucinations or dreams
Flashbulb memories: Unusually vivid and detailed recollections of momentous events - for example,
where you were when you first found out about 9/11
- While they tend to be strong, vivid, and detailed, flashbulb memories actually seem to be less
accurate than once believed - they become less detailed and complete over time
Separation of long-term and short-term memories
The views of short-term and long-term memory as separate came from the idea that short-term
memory was responsible for phonemic encoding while long-term memory was responsible for semantic
encoding - information loss from short-term memory was thought to be based on decay, while
interference was thought to influence long-term memory forgetting
How is knowledge represented and organized?
Clustering: The tendency to remember similar or related items in groups - even though information may
not be organized into groups, participants will still remember them in bundles
Conceptual hierarchy: A multilevel classification system based on common properties among items - this
can dramatically improve recall (an example would be that gold is a rare type of metal, and metal is a
type of mineral)
Schema: An organized cluster of knowledge about a particular object or event, created based on
previous experience with the object or event - people are more likely to remember things that are
consistent with their schemas, but conversely, they are also more likely to remember things that are
drastically different from their schemas
- We have schemas about specific people, types of people, social events, locations
- Relational schemas: Representations of events surrounding interpersonal interactions, which
represent regularities in your interpersonal experience - these affect the way you process
information about others and yourself, and influence your expectations and beliefs about yourself
Semantic network: Nodes representing concepts, joined together by pathways linking related concepts the length of each pathway represents the degree of association between two concepts, with shorter
pathways implying stronger association
- This is helpful to explain why thinking about one word (bread) can make a closely related word
(butter) easier to remember - our thoughts naturally go to related words, which is termed
spreading activation within a semantic network
- This spreads out along the pathways of the semantic network surrounding the initial word, with its
strength decreasing as it travels outward like a ripple in a pond
Connectionist network/Parallel distributed processing (PDP) model: Assume that cognitive processes
depend on patterns of activation in highly interconnected computational networks that resemble neural
networks
- Consists of a large network of interconnected computer units, called nodes, which operate like
neurons - these may be inactive, or there may be excitatory or inhibitory signals to other units
- A specific node's level of activation reflects the balance of excitatory and inhibitory input
- These models assert that specific memories correspond to particular patterns of activation in the
networks
Connectionist and semantic networks sound similar, but there's a crucial difference - in semantic
networks, nodes represent specific concepts or pieces of knowledge, while in connectionist networks, a
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networks, nodes represent specific concepts or pieces of knowledge, while in connectionist networks, a
piece of knowledge is represented by a pattern of activation across an entire network
In connectionist networks, the information lies in the strength of its connections, which is why Parallel
Distributed Processing is called connectionism
Retrieval: Getting Information Out of Memory (p. 298)
There is a difference between the availability and accessibility of information in memory - the
information may not be in your memory, or you may simply fail to retrieve it at the time
Tip-of-the-tongue phenomenon: Temporary inability to remember something you know, accompanied
by a feeling that it's just out of reach - a failure in retrieval, but the exact mechanisms are a subject of
debate
Memories can be jogged with retrieval cues - stimuli which help you access your memories
Encoding specificity principle: Proposes that your memory for information is better when the conditions
during encoding and retrieval are similar - cues used at retrieval will facilitate recall if they were stored
in your memory at the same time as the required information
Trying to recall an event by putting yourself back into the context is working with context cues - for
example, when you plan to get something (scissors, a glass of milk) in your bedroom, then forget what
you were looking for by the time you reach the kitchen… only to remember what you wanted when you
return to your bedroom
Reinstating the context of an event has been used effectively in legal investigations to enhance
eyewitness recall
Recall also seems to be affected by state and mood as well - matching a person's internal state of
encoding at the retrieval phases works as well as matching their external state
These effects may account for amnesia in perpetrators of violent crime - when the crime is carried out in
a state of rage, retrieval after calming down may be hampered
Reconstructing memories
Memories aren't perfect copies - they tend to be reconstructions of the past that are distorted in many
ways
Part of what we recall is the details of the event, and part Is a reconstruction based on schemas of how
it should have been
Misinformation effect: Occurs when participants' recall of an event they witnessed is altered by
introducing misleading post-event information - this often occurs in eyewitness testimonies, as lawyers
badger the witnesses
In tests, when subjects were asked about a video they viewed of cars "smashing into each other" as
opposed to "hitting each other", those in the first group recalled there being broken glass after the
accident when there wasn't - this was consistent with their schema for cars smashing into each other
Source and Reality Monitoring
Source monitoring: Process of making attributions about the origins of memories - memories aren't
labelled by where they came from, so the source of the memory has to be determined at the time of
retrieval (did I read this in the newspaper, or did my friend tell me about it?)
Source-monitoring errors occur when memories derived from one source are misattributed to another yet people often feel confident about their attributions even though the recollections are inaccurate
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Eyewitnesses can be lead to "remember" seeing something verbally suggested to them - this is a sourcemonitoring error, as the memory comes from someone else, yet they feel confident in having seen it
themselves
Reality monitoring: The process of deciding whether memories are based on external sources (actual
experiences) or internal sources (thoughts and imaginations) - for example, trying to decide whether
something happened or if it was just a dream
Forgetting: When Memory Lapses (p. 301)
We need to forget information that is no longer relevant - forgetting reduces competition among
memories, allowing better recall of relevant information
Forgetting can be caused by defects in encoding, storage, and retrieval
Ebbinghaus and forgetting curves
Ebbinghaus forced himself to memorize nonsense syllables, meaningless arrangements of letters, so
his forgetting wouldn't be influenced by previous learning
He then tested himself on his recall as time went on, producing a forgetting curve
Forgetting curve: Graphs retention and forgetting over time
Ebbinghaus's forgetting curve was extremely steep, leading him to conclude that most forgetting occurs
very rapidly after learning
Forgetting isn't actually that steep normally - he was working with meaningless material, which most of
don't normally
Measures of forgetting
Different measures of forgetting yield different estimates of how quickly people forget
Retention: The proportion of material retained
Results may be reported in terms of the amount forgotten, or in the amount retained
Retention length: The length of time between the presentation of materials to be remembered and the
measurement of forgetting
Recall measures: Require subjects to reproduce information on their own, without any cues - you would
simply write down whatever you remember
Recognition measures: Require subjects to select previously learned information from an array of
options - subjects have cues to work with, and the answers are right in front of them
Recognition measures tend to yield higher scores than recall measures, when dealing with the same
information
The difficulty of a recognition test depends on the number, similarity, and plausibility of the available
options - two recognition tests can be wildly different
Relearning measure: Require a subject to memorize information a second time to determine how much
time or how many practice trials are saved by having learned it before - saving scores provide an
estimate of their retention
Why we forget
Ineffective encoding: Information may not have been inserted into memory in the first place - this is
called pseudoforgetting
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called pseudoforgetting
- This is usually due to lack of attention
- Poor encoding can also lead to forgetting - phonemic encoding leads to more forgetting than
semantic encoding, for example
Decay: Forgetting occurs because memory traces fade with time - this is an issue of memory storage
- The assumption is that forgetting occurs in the physiological mechanisms for memories - the mere
passage of time produces forgetting
- Decay does affect sensory and short-term memory - but research has yet to show that it affects
long-term memory
- Time that has passed in long-term forgetting is less important than what has happened during the
interval - it depends on the amount, complexity, and type of information the subjects have had to
assimilate in between - this is interference
Interference: People forget because of competition from other material
- The similarity between original material and new material has a large effect on this - as similarity
between the intervening material decreases, the amount of forgetting is also decreased
- Retroactive interference: When new information interferes with the retention of previously
learned information - occurs between the original learning and the test of that learning
- Proactive interference: When previously learned information interferes with the retention of new
information - rooted in learning that comes before exposure to test material
Retrieval failure: When information can't be retrieved due to lack of proper cues - a good retrieval cue is
consistent with the original encoding of the information
- Encoding specificity principle: The value of a retrieval cue depends on how well it corresponds to
the memory code
- Transfer-appropriate processing: When the initial processing of information is similar to the type
of processing required by the subsequent measure of retention - i.e. remembering by semantics,
and testing semantics
- Retrieval failures are more likely when there is a poor fit between the processing done during
encoding and the processing invoked during and by the measure of retention
Repressed memories
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Repressed memories
Repression: Keeping distressing thoughts and feelings buried in the unconscious - this is a type of
motivated forgetting, where the memories are there all along, but their retrieval is blocked
People don't remember anxiety-laden material as easily as neutral material
Some parents accused years later of child abuse have argued that their children's recollections are false
memories created by therapists
The accusations are vehemently denied, and without corroborative evidence, there is no way to reliably
distinguish real memories from false ones
Many psychologists and psychiatrists accept recovered memories of abuse - they argue that sexual
abuse in childhood is far more widespread than people realize, and that it is common for people to bury
traumatic incidents in their unconscious
Sexual abuse by a parent evokes coping efforts that block awareness of the abuse, because that
awareness would interfere with normal child-parent relationships
Skepticism
However, it's also possible that these self-assessments are distorted - people wrestling with emotional
problems may be convinced by therapists that their problems are the result of abuse
Source-monitoring errors and the misinformation effect are good examples of how repressed memories
could actually be false memories
Many repressed memories have also been recovered under the influence of hypnosis - hypnosis tends to
increase memory distortions, while making people feel more confident about their memories
Rebuttal
On the other hand, individuals with a history of sexual abuse alternate between accepting and denying
that any abuse occurred
There is no direct evidence or empirical basis that all repressed memories are created by therapists
Thus, we don't have enough data to estimate which recovered memories are true and which are not,
but we should be careful about accepting these cases, but also not dismiss them right away
This also highlights that memories are imperfect reconstructions of the past
In Search of the Memory Trace: The Physiology of Memory (p. 309)
Memory trace: The physiological basis for memory - there are a variety of approaches to this idea
Biochemistry
Memory formation results in alterations of synaptic transmission at specific sites - specific memories
depend on biochemical changes that occur at specific synapses
Durable changes in synaptic transmission would be the neural building blocks of complex memories
Manipulations of hormone levels after an organism has learned a response can affect memory storage facilitating or impairing it, by changing activity in the amygdala and a variety of neurotransmitter
systems
For example, adequate protein synthesis is necessary for the formation of memories
Neural circuitry
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Neural circuitry
Specific memories may depend on localized neural circuits - memories may create unique, reusable
pathways in the brain for signals to flow along
- For example, a conditioned response to blink in a rabbit can be eliminated by destroying an area in
the cerebellum - presumably, other memories create entirely different pathways in other areas of
the brain
- This makes it possible (in theory) to map out specific neural circuits that correspond to different
types of memories
Long-term potentiation (LTP): A long-lasting increase in neural excitability at synapses along a specific
neural pathway - can affect presynaptic and postsynaptic neurons in the hippocampus
- There is also an opposing effect for forgetting, called long-term depression (LTD) - a durable
decrease in the excitability in a neural pathway
Neurogenesis: The formation of new neurons -this may affect the creation of new neural circuits for
memory
- New brain cells are formed constantly in the dentate gyrus of the hippocampus - manipulations
that suppress neurogenesis in animals lead to memory impairments, while increased neurogenesis
is associated with enhanced learning
- Newly formed neurons are more excitable, so they may be more readily recruited into neural
circuits responding to new memories
- This makes neurons of varying age different - this could provide an opportunity to "time stamp"
certain memories
Anatomy
There are two types of organic amnesia - memory loss due to head injury - retrograde amnesia and
anterograde amnesia
- Retrograde amnesia: The loss of memories before the onset of amnesia
- Anterograde amnesia: Loss of memories for events that occur after the onset of amnesia alternatively, could be the prevention of forming new memories
The hippocampus is crucial to long-term memory, and damage there can lead to amnesia
Different types of memories (older ones, newer ones, ones based on context) may be accessed with
different parts of the hippocampus
Consolidation: A hypothetical process where information is converted into durable memory codes in
long-term memory
- Memories are consolidated in the hippocampal region and stored in various areas of the cortex,
- This allows new memories to be independent of the hippocampal region and be integrated with
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- This allows new memories to be independent of the hippocampal region and be integrated with
other memories
- Much of the consolidation process seems to occur while people are asleep
When it comes to the formation of learned fear responses, the amygdala seems to be responsible
Working memory seems to be handled by the prefrontal cortex
- The central executive component of working memory may be in the prefrontal cortex
- The phonological loop may be localized in areas of the left hemisphere
- On the other hand, the visuospatial sketchpad may be localized in areas of the right hemisphere
Systems and Types of Memory (p. 312)
Implicit vs explicit
Implicit memory: When retention is exhibited on a task that does not require intentional remembering it's incidental, unintentional remembering
- This is unconscious, must be accessed indirectly, and can be assessed with tests of relearning
- Implicit memory, unlike explicit memory, is not affected by amnesia, age, administration of drugs
(such as alcohol), the length of retention interval, or interference
Explicit memory: When intentional recall of previous experience is required
- This is conscious, accessed directly, and can be assessed with tests of recall or recognition
When amnesiacs are tested, they may not explicitly recall information, but they will implicitly recall it
Declarative vs procedural
Declarative memory: Handles factual information - recollections of words, definitions, names, dates,
concepts, etc.
Procedural (nondeclarative) memory: Houses memory for actions, skills, operations, and conditioned
responses - how to ride a bike, typing, etc.
Knowing the rules of tennis is stored in declarative memory, while how to perform a serve is store in
procedural memory
Memory for skills is largely unconscious - thus, implicit memory - and in fact performance may be worse
if people think about what they're doing
Memory for skills also doesn't deteriorate over time
Declarative memory seems to be handled by the hippocampus - the cerebellum seems related to
procedural memory
Semantic vs episodic
Episodic memory: Chronological recollections of personal experiences - the things you've done, seen,
and heard, as well as when you did these things
- This is a kind of mental auto-biography
- We also use episodic memory to simulate what might happen in the future - to pre-experience the
future - as well as re-experiencing the past
Hyperthymestic syndrome: When someone can accurately remember almost everything that has
happened to them
Semantic memory: General knowledge that is not tied to the time when it was learned - these are
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Semantic memory: General knowledge that is not tied to the time when it was learned - these are
general facts, like an encyclopaedia
- This stores things such as the date of Christmas, where Saskatoon is, etc.
Some amnesiacs forget only personal facts, while their recall of general facts is unaffected
Prospective vs retrospective
Prospective memory: Remembering to perform actions in the future - walk the dog, take the meat out of
the freezer after work
Retrospective memory: Remembering events from the past, or previously learned information - who
won the Stanley Cup last year
People vary considerably in their recall of prospective memory tasks - it is easy to forget these kinds of
intentions
One key factor seems to be whether the task is tied to a sort of cue - event-based tasks involve future
actions that should be triggered by something (for example, having to tell your friend something, which
is triggered by seeing them)
Time-based tasks require that an action be completed at a certain time, or after a certain length of time
has passed - there are less cues available here
Age appears to be a factor here - older adults handle event-based prospective tasks better than timebased tasks
Two areas in the frontal lobe seem important for creating plans for the future, but the medial temporal
lobe also contributes
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