Short Term Memory Processes

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Short Term Memory Processes
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Memory Systems
Sensory memory or the sensory register is the
focus of this chapter. How does this system allow
us to do pattern recognition (e.g. the extraction
of information from an environmental scene)

• Each stage requires a Process to move information
  to the next stage.
• From sensory memory to short term memory that
  process is attention
• From short term memory to long term memory that
  process is rehearsal.

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Short Term Memory

• Short term memory is the first memory system
  discussed in this course that is concerned with
  information on a conscious level.
• Based on research studies conducted over the last
  35 years, we can state that short term memory has
  two major characteristics
• -It retains information for a very brief period
  of time, longer than the sensory register
  certainly, but much shorter than LTM
• -It has an extremely limited capacity, as
  opposed to both the sensory register and LTM
  which have very large capacity.
• But for many modern cognitive Psychologists, a
  major question is do we really need to concern
  ourselves with an additional stage to explain
  this research? Perhaps STM is just a set of
  processes that operate between sensory extraction
  and a comparison to LTM information.

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Memory William James

• James proposed that memory had but two stages,
  primary memory (e.g. STM), and secondary memory
  (e.g. LTM).
• Primary memory consisted of the contents of
  consciousness. That is, information under active
  consideration at the moment.
• Primary memory was subject to the limitations of
  the conscious span, thus it involved information
  only in the active conscious state,
• Thus it was quite short and subject to the
  capacity and duration limits of consciousness.
• Secondary memory was information in an inactive
  state. The primary source of information in STM
  came from LTM, but LTM is not a different place
  or stage!

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The Atkinson-Shiffrin Model

• A product of the 1960s and computer modeled,
  mechanical, stage information systems.
• STM and LTM are conceptualized as occurring in
  different places and at different stages.
• This model is so well know it is known as the
  stage model, and it concentrates on factors
  occurring in STM, designated as control
  processes.

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Characteristics of STM

• STM is defined as a conceptual system which not
  only stores information for a brief time, but
  also serves as a workspace for rehearsing,
  coding, retrieving, and decision making
• STM is defined mainly by its characteristics
  the control processes that occur at this stage.
• Control Processes
• Rehearsal Rehearsal serves two main functions,
  1) to maintain information in STM, and 2) to
  transfer information information from STM to LTM.
• Coding Coding involves 1) attaching information
  from long term memory to code it into larger
  units (chunking). 2) using a retrieval strategy
  to get information from LTM (e.g. which
  characteristic of the information will your
  retrieve, name, sound, ect). Information is
  converted to an acoustic code
• Characteristics
• Trace Life Characterized by a very brief trace
• Storage Capacity Characterized by very limited
  capacity
• Nature of the code Characterized by a phonetic
  code

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Evidence for STM

• Evidence for Rehearsal comes from the
  Brown-Peterson procedures utilizing rehearsal
  interference
• 3 or 4 items are memorized and then memory for
  those items is tested.
• In some trials an articulatory suppression or
  rehearsal prevention procedure is used.
• Evidence for coding processes comes from studies
  showing that when the interference task is in the
  same modality as the two be remembered
  information the interference is greater

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Evidence for STM

• Evidence for capacity comes from chunking studies
  
• Evidence also comes from the primacy and recency
  studies demonstrating the primacy/recency

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Chunking

• F B I T W - A C I A I B - M

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Chunking
Repeat the information your just saw
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Chunking

• FBI TWA CIA IBM

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Chunking
Repeat the information your just saw
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Serial Position Effect

• The phenomenon occurs due to the effects of
  Primacy Recency
• Primacy means that the first few items in a list
  of material are remembered better than items in
  the middle of the list
• Recency means that items at the end of the list
  are remembered better than items in the middle of
  the list.
• List is hypothesized to occur due to the nature
  of long term memory

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Neurological Correlates of Short Term Memory

• Electrical recording from cortical areas in
  monkeys have identified areas of the frontal
  lobes that become active when the monkeys are
  required to actively hold information they will
  be required to view, but are not yet viewing.
• These neurons are connected to areas in the
  parietal lobe that contain representations of our
  spatial environment.
• Additional neurons in the frontal lobes that
  become active during short term memory tasks are
  linked to areas of the temporal lobes which are
  specialized for short term object memory.
• This suggests that these areas of the frontal
  lobes are acting as a brief maintenance area for
  spatial and object related information, a direct
  neural correlate for short tem memory
  (Goldman-Rakic, 1987).
• PET Studies have also confirmed that humans
  demonstrate similar patterns of activation when
  engaged in short term memory tasks (Smith et.
  al.)
• The picture that emerges is one in which that
  short term memory is represented by brief
  activation in the frontal lobes with permanent
  information stored in posterior areas of the
  brain.

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Neurological Correlates of Short Term Memory

• So perhaps memory is just a highly activated form
  of information (William James), or a set of
  processes that work with long term memory.

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Working Memory An Alternative Explanation.

• Working Memory is the system that allows
  information selected from the sensory register to
  be acted upon.
• Working memory is an efficient processor that
  allows rapid access to information necessary for
  executing cognitive processes.
• Working memory has a limited capacity that
  necessitates trade offs between storage
  computational processes (although these capacity
  limits can be expanded in various ways).
• The contents of working memory change dynamically
  according to the demands of of ongoing cognitive
  processes

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Working Memory
Working Memory
Sensory Register
LTM
This system grabs information off the sensory
register and acts on it. To do this it must have
reciprocal connections with LTM
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Working Memory An Alternative Explanation.

• Working Memory consists of two major processing
  systems, a phonological rehearsal loop and a
  visuospatial sketch pad, controlled by a central
  executive system.
• It extends mental processes over time and
  produces temporary results that are needed by
  other sub processes (e.g. memory storage).
• Some of the temporary processes that working
  memory engages in are 1) search comparison, 2)
  numerical transformation, 3) language
  comprehension, and 4) problem solving.
• Working memory supports these operations by
  holding intermediate results and scheduling the
  coordination of the component processes

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Working Memory Additional Components

• In addition to the visuospatial sketch pad
  researchers have also uncovered evidence for two
  other types of information maintained in working
  memory
• 1) Procedural knowledge, and 2) abstract semantic
  knowledge.
• There are perhaps other types of information
  maintained and operated on in working memory that
  researchers have not yet identified (e.g. tactile
  knowledge or motor knowledge)

Sketch Pad
Procedural Knowledge
Phonological Loop
Central Executive
Abstract Semantic Knowledge
?
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Next Weeks Reading

• Ch Hunt Ellis ch 4
• Honeck-Episodic memory article (tulving)