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


  • Thought to be 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)
• A key issue with historical psychological research, particularly concerning Jacobs, is the lack of standardisation and appreciation of scientific methods
• The current laboratory experiment methodology produces highly reliable and valid data through controlling and so removing the effects of extraneous and confounding variables
• Bahrick et al's 1975 study has high ecological validity because it uses meaningful stimuli and a methodology which is high in mundane realism
• The Petersen et al and Miller et al studies have low mundane realism, thus producing findings with little ecological validity
• More recent research has suggested that Miller may have over-exaggerated the capacity of STM, and that the capacity is more similar to 4 chunks as opposed to the original 5-9 limit
• Multi-Store Memory Model (MSM)


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

  
• 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
  • Has 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 allows information to pass into LTM
• Long-term memory (LTM)


  • Semantically encoded
  • Unlimited capacity
  • Very long duration (over 46 years)

  
• The MSM does not represent different types of LTM (procedural, semantic, episodic) or that some types of LTM can be retrieved unconsciously
• The MSM suggests that the amount of maintenance rehearsal determines the likelihood that information will pass into LTM, whereas Craik and Watkins suggest that the type of rehearsal is more important
• Multi-Store Memory Model


  • Acknowledges qualitative differences between STM and LTM
  • Incorrectly represents STM as a single, unitary store
• Episodic memory


  Memories which have personal meaning, alongside details of when, how, who and where the events occurred
• 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 that semantic memories were recalled from the left prefrontal cortex, whilst episodic memories were recalled from the right prefrontal cortex

  
• Belleville et al notes that mild cognitive impairments most commonly affect episodic memories
• Cohen and Squire drew a distinction between declarative (conscious recall) and non-declarative (unconscious recall) memories, which is different to Tulving's classification

  
• The cases of HM and Clive Wearing show how one type of LTM may be impaired (episodic) while other types (procedural, semantic) remain unaffected
• Working Memory Model (WMM)

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

  
• Central executive


  • An 'attentional process' with a very limited processing capacity, whose role is to allocate 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 and links STM to LTM
• The central executive has not been precisely defined, which draws doubts about the accuracy of the WMM's depiction of working memory
• Shallice and Warrington's study of KF supports the WMM by showing separate components for auditory and visual STM
• Dual-task performance studies support the WMM's idea of the central executive having a limited processing capacity
• Neuroscanning evidence supports the role of the central executive in allocating tasks and having a limited capacity
• Interference


  Occurs when the recall of one memory blocks the recall of another, causing forgetting or distorted perceptions
• Retroactive interference


  • New memories block the recollection of old memories