Richard Griffiths - Lecture Notes

Memory 

The Components of Human Memory

Systems diagram of memory components, sensory, short term, long term.

Not clear if these are really three distinct sub-systems or different functions of the same system.

Sensory Memory

Input buffers for each input channel.
Information is passed into short-term memory by being attended to — concentrating on one out of a number of available stimuli.  However, the processing of speech shows that conscious attention comes into play after a considerable amount of processing has been done.  Cocktail party phenomenon.

Visual —Iconic memory

“Writing” with sparklers.
Persists for approx. 0.5 seconds.

Aural (sound) — Echoic memory

Allows brief play-back

Touch — Haptic memory

Short-term Memory

Is the working store.
Can be accessed rapidly, approx. 70 ms.
Decays rapidly, approx. 200 ms.
Channels appear to be separate.

Capacity

Has a limited capacity, Miller’s 7 ± 2 chunks of information.
I.e., a chunk is the result of a coding that increases information density.
Formation of a chunk is known as closure.

Recency

The sequence of presented items is also significant.  Last items presented are more easily remembered than earlier.  Recency effect.  However, a task intervening between presentation and recall eliminates recency effect.  Earlier items are held in long-term memory.

Long-term Memory

Not capacity limited.
Slow access time of approx. 0.1 seconds.
Forgetting occurs slowly, and may not actually happen at all.

Types of memory

Episodic memory
Memory of events and experiences in a serial form.
Semantic memory
Structured record of facts, concepts and skills that we have acquired.
Number of different data structure proposed;
  • Semantic Networks
  • Frames and Scripts
  • Production Rules
  • Semantic Networks and Prototypes
    Represent associations and relationships between single items in memory.
    Knowledge organised by association.
    Evidence for semantic net organisation, Collins and Quillian.  Concepts semantically distant took longer to recall than concepts semantically close.
    Frames and scripts
    Allow the representation of more complex objects and events, composed of a number of items and activities.
    Proposed to account for holding of different types of knowledge.
    Frames and scripts organise information into data structures.
    Slots in the structures allow attribute values to be held, and may contain default, fixed or variable information.
    Frames
    Extend semantic nets to include structured, hierarchical information.
    Make explicit the relative importance of each piece of information.
    Scripts
    Represent stereotypical knowledge about situations - for example, sequence.
    Production Rules
    “If condition then action” rules.
    Encode procedural knowledge.

    E.g.,

    If glass is empty then fill glass.

    If glass contains beer then drink it.

    Processes

    There are three main processes associated with the operation of memory;
  • Storage or Remembering
  • Forgetting
  • Retrieval
  • Storage or Remembering
    Requires repeated exposure or rehearsal.
    Total time hypothesis
    Ebbinghaus: The amount learned is directly proportional to amount of time spent learning.
    Distribution of practice effect
    Baddeley: Learning time is most productive if is distributed over time.
    Semantic content
    Meaningful information is easier to remember.
    A list of  words representing concepts is more difficult to remember than a set of words representing objects.

    E.g.,
    Expensive Big Soft Fast  Sticky Ductile Hot Trite Sweet Smooth
    vs.
    Slug Battery Man Pencil Ship Arm Scissors Cup Door Book

    Meaningful information may be distorted by cultural expectations, Bartlett.

    Forgetting
    Two main theories:  Decay and Interference
    Decay
    Information decays logarithmically - more rapidly to begin wit.
    Jost’s law: If two memory traces are equally strong at a given time, the older one will be more durable.
    Interference
    New information causes loss of old information - retroactive interference.
    However, sometimes old information may interfere with the learning of new - proactive inhibition.
    Is memory ever lost?
    Could simply be a problem with retrieval.
    E.g., “Tip of the tongue” phenomenon.
    Retrieval
    Two types of retrieval:  Recall and Recognition
    Recall
    Information is reproduced from memory.
    If the person is allowed to categorise or structure the information, it assists recall.
    The Greek art of memory, the method of locations.
    Recognition
    Presentation of the stimulus evokes awareness that it has been experienced previously.

    References

    Anderson, J. R.  1985  "Cognitive Psychology and Its Implications" (Second Edition).  W.H. Freeman and Company, New York.

    Dix, A., Finlay, J., Abowd, G., Beale, R.  1998  “Human-Computer Interaction” (Second Edition).  Prentice Hall.
     
     
     

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