Short Term Memory

• short term memory is a unitary store
• separate from long term memory
• maintanence rehearsal prevents decay
• capacity

  the amount of information that can be held in a memory store
• encoding

  the format in which information is stored in the various memory stores
• duration

  the length of time information can be held in memory
• capacity of STM

  7+/-2
• durationof STM

  18-30 seconds
• encoding of STM

  acoustic
• Miller (1956)

  • to test digital span, participants are presented with number lists of increasing length and then asked to recall them
  • generally participants are able to recall between 5 and 9 items or chunks of information
  • this represents the capacity of STM
• evaluation of capacity

  • a rule or mnemonic can be used to chunk information together, allowing STM to hold more
  • capacity was found to be around 4 chunks in a review by Cowan (2001), meaning the upper end of Miller's range is not supported by evidence
• Peterson and Peterson

  • the duration of STM is between 18-30 seconds
  • in order to measure duration, participants are asked to recall a stimulus after a set time interval
  • presented participants with trigrams and asked them to recall after varying intervals
  • when rehearsal is prevented (using a counting backwards task), accuracy of recall reduces
• Baddeley

  • encoded acoustically
  • when letters in a list are acoustically similar they get mixed make it harder for you to recall the correct order
  • acoustic similarity effect
• limitiation of Peterson and Peterson

  • study was artificial conducted in a lab using meaningless trigrams
  • does not reflect real-life memory
  • lacks mundane realism
  • lacks validity
• strength of Peterson and Peterson

  • standardised
  • minimises extraneous variables that could have interfered with participant's recall
  • high reliability