coding, capacity and duration

• short term memory is the memory for things which are present or just happened
• long term memory is the memory for things that happened in past
• capacity is how much info can be held in memory at one time
• coding is how info is stored in memory
• duration is how long info can be held in memory
• short term memory

  capacity = 5-9 items

  coding = acoustic

  duration = 18-30 seconds
• long term memory

  capacity = unlimited

  coding = semantic

  duration = unlimited
• key study for capacity - Jacobs

  • got participants to recall 4 digits in correct order and outloud - repeated task increasing number of digits until mistake
  • found average digit span of 9.3
• digit span is the number of items individuals can correctly recall
• key study in capacity - Miller

  • idea that things come into groups of 7 (days of week)
  • suggests we are predisposed to remembering quantity
  • chunking helps aid recall
• chunking is grouping sets of digits/letters into chunks
• evaluation for capacity - individual differences

  • jacobs found digit span increases with age as result of developing strategies such as chunking
  • goes against own findings
• evaluation for capacity - capacity of STM

  • contradictory research suggests capacity of STM is actually 4 items - suggesting lower end of millers range is more appropriate
• key study in coding - Baddeley

  • 4 groups of participants (acoustically similar, acoustically dissimilar, semantically similar and semantically dissimilar)
  • participants were shown original words + asked to recall in order
  • when recalling immediately after - did worse on acoustically similar words
  • when recalling after 20 minutes they did worse on semantically similar
• evaluation for coding - LTM not fully semantic

  • research against LTM coded semantically as researchers found evidence of acoustic coding in LTM
• evaluation for coding - questions about Baddeleys study for coding in memory

  • baddeley may not have been testing LTM because latest recall is only after 20 min
  • lab experiments used with artificial stimuli which limites reliability of findings.
• key study for duration of LTM - bahrick

  • used graduates from high school aged 17-74
  • conducted recall test from using yearbook
  • free recall - recall participants named with no cue (15 years - 60% accuracy, 48 years - 30% accuracy
  • photo recognition test (15 years - 90%, 48% - 70%)
• evaluation for key study duration of ltm - external validity

  • bahrick et al has high external validity were findings can be generalised - years go on the lower recall % will be
• evaluation for key study duration of ltm - low levels of control

  • many variables which may have affected recall such as rehearsal (looking at yearbook)and popularity - disrupting desired results
• key study for duration of stm - peterson and peterson

  • gave participants trigram to remeber
  • then got them to count back from 3 digits till told to stop (time stopped varied - 3,6,9,12)
  • found the longer the interval the less accurate the recall
• a trigram is 3 digits
• retention interval is the period between participants exposure to info and being tested for retention of info
• evaluation for key study of duration for stm - external validity

  • peterson and peterson has low external validity where findings have limited generalisability due to artificial memory test
• evaluation for key study of duration for stm - displacement

  • may have been that letters have been displaced by the counting rather than forgetting the information