Memory

• Coding


  The format or 'type' of information which is stored in each memory store
• Coding in memory

  • Acoustic in short-term memory, semantic in long-term memory
• Capacity


  The volume of information/data which can be kept in any memory store at any one time
• Capacity of STM

  • 7 +/- 2 items (Miller)
• Capacity of LTM

  • Unlimited
• Duration


  The amount of time that information can be stored in each memory store
• Duration of STM

  • 18-30 seconds (Petersen et al)
• Duration of LTM

  • Unlimited (Bahrick et al)
• Bahrick et al's 1975 study has high ecological validity due to the use of meaningful stimuli and a methodology with high mundane realism
• The Petersen et al and Miller et al studies have low mundane realism, producing findings with little ecological validity due to the use of artificial stimuli
• More recent research suggests Miller may have over-exaggerated the capacity of STM, which is more similar to 4 chunks
• Multi-Store Memory Model (MSM)


  Represents how memory is stored, transferred between the different stores, retrieved and forgotten

  
• Memory stores in the MSM

  • Sensory register
  • Short-term memory
  • Long-term memory

  
• Sensory register


  • Contains one sub-store for each of the 5 senses, has a huge capacity but a duration of less than half a second
• Short-term memory (STM)

  • Acoustically encoded, capacity of 7 +/- 2 items, duration of 18-30 seconds
• Maintenance rehearsal


  Repeating new information to oneself, allowing it to be kept in STM
• Long-term memory (LTM)

  • Semantically encoded, unlimited capacity, very long duration (over 46 years)
• Retrieval


  When information is transferred back into the STM
• The MSM does not represent different types of LTM (procedural, semantic, episodic) or that some can be retrieved unconsciously
• The MSM suggests the amount of maintenance rehearsal determines if information passes to LTM, but Craik and Watkins suggest the type of rehearsal is more important
• Multi-Store Memory Model

  • Acknowledges qualitative differences between STM and LTM, portrays accurate view of differences

  
• The MSM incorrectly represents STM as a single, unitary store
• Episodic memory


  Memories with personal meaning, details of when and how events occurred, associated people and places
• Semantic memory


  Memories of the world and associated knowledge
• Procedural memory


  Memories of learned skills
• Episodic and semantic memories must be recalled consciously, whereas procedural memories are recalled unconsciously
• Petersen et al. demonstrated semantic memories were recalled from the left prefrontal cortex, whilst episodic memories were recalled from the right prefrontal cortex
• Differentiating between types of LTM has practical applications, e.g. in treating mild cognitive impairments
• Cohen and Squire's distinction between declarative and non-declarative memories is different to Tulving's classification of LTM types
• Cases of HM and Clive Wearing support the idea of different types of LTM with separate neurological bases
• Working Memory Model (WMM)

  Suggests STM is made up of the central executive, phonological loop, visuo-spatial sketchpad and episodic buffer
• Central executive


  • An 'attentional process' with limited processing capacity, allocates tasks to the 3 slave systems
• Phonological loop


  • Processes auditory information and allows for maintenance rehearsal
• Visuo-spatial sketchpad


  • Combines visual and spatial information, capacity around 4-5 chunks
• Episodic buffer


  • Integrates all types of data processed by the other stores, links STM to LTM
• The central executive has not been precisely defined in the WMM
• Shallice and Warrington's study of KF supports the WMM by showing separate auditory and visual STM components
• Dual-task performance studies support the WMM's idea of the central executive having limited processing capacity
• Neuroscanning evidence supports the role of the central executive in the WMM
• Interference


  When the recall of one memory blocks the recall of another, causing forgetting or distorted perceptions