PSY100H1 Chapter Notes -Short-Term Memory, Long-Term Memory, Echoic Memory

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10 Nov 2011
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Chapter 7 Memory
- memory – the capacity of the nervous system to acquire and retain usable skills and knowledge, allowing living organisms
to benefit from experience
- our memories are often incomplete, biased, and distorted
- memory is a story that can be subtly altered though telling and retellings
What are the basic stages of memory?
- since late 1960s, most psychologists have viewed memory as a form of info processing in which memory processes occur in
much the same way as they do in a computer
- from an information processing perspective, the common way to describe memory is through a three stage memory system
that involves sensory memory, short term memory and long term memory
- modal memory model – the three stage memory system that involves sensory memory, short term memory, and long term
- modal refers to the model’s being common or standard
- Atkinson and Schiffrin – 1968 – the modal model has dominated psychological thinking about memory, in spite of its being
somewhat inaccurate and incomplete
Sensory memory is brief
- sensory info leaves a trace on the nervous system for a split second and then vanishes
- sensory memory – memory for sensory info that is stored briefly in its original sensory form
- visual memory is also called iconic memory, whereas auditory sensory memory is also called echoic memory
- iconic memory persisted for about 1/3 of a second, after which the sensory memory trace faded and was no loner accessible
- iconic and echoic memory allow us to experience the world as a continuous stream rather than in discrete sensations, much
the same way that a movie project plays a series of still pictures that follow each other closely enough to look like
continuous action
Short term memory is active
- short term memory (STM) – a limited capacity memory system that holds info in awareness for a brief period of time
- many contemporary researchers use the term immediate memory to emphasize the idea that this temporary buffer consists
of our fleeting thoughts, feelings, and impressions of the world
- short term or immediate memory can hold info for no longer than about 20 seconds
- it then disappears unless you actively prevent that from happening by thinking about the info or rehearsing it
- memory span and chunking
o short term memory is a limited resource that can hold only so much info
o Miller – STM is generally limited to about seven times, plus or minus two, which is commonly referred to as
memory span
o Memory span varies among individuals
o Some tests of intelligence use memory span as a measure of IQ
o Memory span is limited to at most seven items, and probably fewer, but the items can be letters, numbers, words,
or even concepts
o Meaningful units are easier to remember than nonsense units
o Process of organizing info into meaningful units is known as chunking, as in breaking down the info into chunks
o The more efficiently you chunk info, the more you can remember
o The greater your expertise with the material, the more efficiently you can chunk info and therefore the more you
can remember
o Ability to chunk info efficiently relies on our long term memory system
- Working memory
o Initial conception of short term memory was that it was simply a buffer in which verbal info was rehearsed until it
was stored or forgotten
o STM is not a single storage system but rather an active processing unit that deals with multiple types of info, such
as sounds, images, and ideas
o Baddeley – influential model of a three part active memory system that they called working memory
o Working memory – an active processing system that keeps different types of info available for current use
o Three components of working memory
central executive
presides over the interactions between the subsystems and long term memory
it’s the boss
encodes info from sensory systems and then filters info that is sufficiently important to be store
din long term memory
retrieves info from long term memory as needed
relies on 2 subcomponents that temporarily hold auditory or visual info
the phonological loop
encodes auditory info and is active whenever you read, speak, or repeat words to yourself fin
order to remember them
recall is poorer when many words on a list sound the same compared to when they sound
dissimilar, even when the latter words are related to each other in meaning
words are processed in working memory by how they sound rather than by what they mean
the visuospatial sketchpad
processes visual info
distinction between phonological loop and visuospatial sketchpad has been demonstrated by
studying patients with specific brain damage
Long term memory is relatively permanent
- long term memory (LTM) – the relatively permanent storage of info
- distinguishing long term memory from short term memory
o long term memory is distinct from short term memory in 2 ways – duration and capacity
o controversy exists as to whether LTM represents a truly different type of memory storage from STM
o serial position effect – ability to recall items form a list depend son order of presentation, with items presented
early or late in the list remembered better than those in the middle
o primacy effect – in a list, the better memory for items presented first
o recency effect – in a list, the better memory for words presented later in the list
o the idea that primacy effects are due to LTM whereas recency effects are due to STM is supported by studies in
which there is a delay between the presentation of the list and the recall task
o such delays interfere with the recency effect, but not the primacy effect
o recency effect even for info presented over days and weeks, which makes it unlikely that the material is being
maintained in STM
o recency effect on its own doesn’t prove that STM and LTM are really different types of memory storage
o best support for distinction between STM and LTM can be found at biological level of analysis in case studies
o LTM can be dissociated from STM
o Two memory systems are highly interdependent
o To chunk info in STM, people need to form meaningful connections based on info stored in LTM
- What gets into long term memory
o Info enters permanent storage through rehearsal
o Overlearning, in which you keep rehearsing material that you already known pretty well, leads to improved
memory, especially over longer periods of time
o Studying that is spread out over time, distributed practice, is better remembered tan material that is studied in a
brief period of time, called massed practice or cramming
o Only info that helps us adapt to environment is typically transferred from short term to long term memory
o By storing info that is meaningful, organisms can benefit from experience
o Evolutionary theory helps explain how we decide in advance what info will be useful
o Memory that allows us to use info in a way that assists in reproduction and survival
What are the different memory systems?
- until last few decades, most cognitive psychologists thought long term memory was a relatively unitary system
- memories were viewed as differing in terms of strength and accessibility, but generally they were considered to be of the
same type
- Tulving, Schacter, Squire – memory is not just one monolithic entity, but are a process that involves a number of interacting
- Although systems share a common function – to retain and use info – they encode and store different types of info in
different ways
- Some researchers have distinguished among memory systems based on how info is stored in memory, such as whether the
storage occurs with or without deliberate effort
- Method of storage often differs depending on the type of info being stored
Explicit memory involves conscious effort
- most basic distinction between memory systems is between those for which we consciously remember and use info and
those for which memory occurs without conscious effort or intention
- explicit memory – the processes involved when people remember specific info
- declarative memory – the cognitive info retrieved form explicit memory; knowledge that can be declared
- many use the terms interchangeably, but explicit memory refers to the process of memory whereas declarative memory
refers to the content of memory
- declarative memories can involve words or concepts, visual images, or both
- 1972 – Tulving – introduced a further distinction in explicit memory between episodic and semantic memory
- episodic memory – memory for one’s personal past experiences
- semantic memory memory for knowledge about the world
- evidence that episodic and semantic explicit memory systems are separate can be found in cases of brain injury in which
semantic memory is intact even though episodic memory is impaired
Implicit memory occurs without deliberate effort
- implicit memory – process by which people how an enhancement of memory, most often through behaviour, without
deliberate effort and without any awareness that they are remembering anything
- implicit memory pervades daily experiences
- does not require attention
- happens automatically and without deliberate effort
- procedural memory – a type of implicit memory that involves motor skills and behavioural habits – motor memory
- procedural memories have an automatic, unconscious aspect to them
- implicit memory influences our lives in subtle ways
- many of our attitude are formed through implicit learning
- repetition priming the improvement in identifying or processing a stimulus that has previously been experienced
How is information organized in long term memory?
- events that are sufficiently important to be remembered permanently need to be stored in a way that allows for later
- memories are stored in an organized fashion
Long term memory is a temporal sequence
- memory can be divided temporarily into 2 processes, encoding, storage, and retrieval
- encoding – the processing of info so that it can be stored
- whether simple or complex, info is stored in networks of neurons in the brain
- storage – the retention of encoded representations over time that corresponds to some change in the nervous system that
registers the event
- stored resentations are referred to as memories
- memories represent many different kinds of info such as visual images, facts, ideas, tastes, or even muscle movement
- retrieval – act or recalling or remembering stored info in order to use it
- act or retrieval often involves an explicit effort to access the contents of memory storage
- many times, you retrieve info implicitly, without any effort at all
- retrieval is involved in both explicit and implicit memory systems
Long term storage is based on meaning
- memories are stored by meaning
- levels of processing model – the more deeply an item is encoded, the more meaning it has and the better it is remembered
- maintenance rehearsal - a type of encoding that involves continually repeating an item
- elaborative rehearsal – the encoding of info in a more meaningful fashion, such as linking it to knowledge in long term
- at the biological (brain systems) level of analysis, brain imaging studies have shown that semantic encoding activates more
brain regions than shallow encoding
- this greater brain activity is associated with better memory
Schemas provide an organizational framework
- people store memories by meaning
- decisions about how to chunk info depend on pervious organizational structures in long term memory
- schema – a hypothetical cognitive structure that helps us perceive, organize, process, and use info
- they help us sort out incoming info and guide our attention to relevant features of environment
- people use past memories and general knowledge about world to shape incoming info
- by doing so, they construct new memories fill in holes, overlook inconsistent info, and interpret meaning on basis of past
- existing schemas help us make sense of world, but they can lead to biased encoding
- schemas influence which info is stored in memory
Information is stored in association networks
- one highly influential set of theories of memory organization is based on networks of associations
- network models of memory emphasize the links between semantically related items