coding capacity and duration of memory

• short term memory?

  limited capacity memory store. coding mainly acoustic, capacity between 5 and 9 items on average or 7 +- 2 and duration is about 18 seconds
• long term memory?

  permanent memory store. coding is semantic, capacity is unlimited and it can store memories for up to a lifetime
• coding?

  format in which information is stored in various memory stores
• capacity?

  amount of information that can be held in a memory store.
• duration?

  length of time information can be held in a memory store.
• baddeley's research on coding?

  -gave different lists of word to 4 groups of participants

  -group 1 acoustically similar, group 2 acoustically dissimilar, group 3 semantically similar and group 4 semantically dissimilar.

  -participants were shown original words and asked to recall them in correct order.

  -when recalling from STM (immediately), did worse with acoustically similar words. when recalling from LTM (after 20mins), did worse with semantically similar words.
• peterson and peterson's research on duration of STM?

  -tested 24 students in 8 trials each

  -given consonant syllable to remember and a 3 digit number to count back from until told to stop to prevent mental rehearsal.

  -in each trial told to stop after varying periods of time. (3,6,9,12,15,18secs)

  -after 3 secs recall was about 80%, after 18 secs recall was about 3%.
• bahrick et al research on duration of LTM?

  -392 american participants aged between 17 and 74 and their HS yearbooks obtained

  -tested recall in various ways. (1)photo recognition test and (2)free recall test where recalled names of their graduating class.

  -those tested within 15 years of graduation, 90% accurate in photo recognition test. after 48 years recall declined to about 70%.

  -for free recall test, after 15 years 60% and after 48 years 30%.
• jacobs research on capacity (digit span)?

  -measured digit span. researcher reads out 4 digits and participants recalls out loud in correct order. if correct researcher reads out 5 digits and so on until participant gets it wrong.

  -found mean span for digits was 9.3 items and for letters was 7.3 items.
• millers research on capacity (chunking)?

  -made observations of everyday practice, noted that things come in 7s like days of the week, 7 notes on musical scale and 7 deadly sins.

  -so span is 7 items +/- 2

  -noted that people can recall 5 words as easily as 5 letters. do this by chunking.
• strength of baddeley's study?

  P - identified clear difference between 2 memory stores.

  E - later research showed there are some exceptions to baddeley's findings but idea that STM uses acoustic coding and LTM uses semantic has stood test of time.

  L - important step in our understanding of memory system which led to MSM.
• limitation of baddeley's study?

  P - used artificial stimuli rather than meaningful material

  E - word lists have no personal meaning to participants so his findings may not tell us much about coding in different kinds of memory tasks especially in everyday life. when processing more meaningful info, people may use semantic coding even for STM tasks

  L - findings have limited application
• strength of jacobs study?

  P - has been replicated

  E - some participants digit spans might have been underestimated as they were distracted during testing however jacob's findings have been confirmed by better controlled studies since. (bopp and verhaeghen)

  L - valid test of digit span in STM
• limitation of millers research?

  P - may have overestimated STM capacity

  E - cowan reviewed other research and concluded that the capacity of STM is only about 4 +/- 1 chunks

  L - the lower end of millers estimate (5 items) is more appropriate than 7 items
• limitation of peterson and peterson's study?

  P - stimulus material was artificial.

  E - study isn't completely irrelevant as we do sometimes try to remember meaningless material but recalling consonant syllables doesn't reflect everyday memory activities where what were trying to remember is meaningful.

  L - lacked external validity
• strength of bahricks study?

  P - high external validity

  E - researchers investigated meaningful memories. when studies on LTM were conducted with meaningless pictures to remembered recall rates were lower.

  L - findings reflect a more real estimate of duration of LTM.