coding, capacity and duration

• coding

  = format in which information is stored in the various memory stores.

  • process of converting information between different forms.
• research-coding

  = Baddeley gave different lists of words to 4 groups of participants to remember:

  -1 acoustically similar, 2 acoustically dissimilar, 3 semantically similar, 4 semantically dissimilar

  • participants shown original words and asked to recall them in correct order.
  • when recalling form STM, worse with acoustically similar words.
  • when recalling form LTM, worse with semantically similar words.
  • suggests information is coded acoustically in STM, and semantically in LTM.
• capacity

  = the amount of information that can be held in a memory store.
• research-capacity

  digital span

  • Jacobs found out by measuring digit span, eg: researcher reads out 4 digits and participant has to recall them in the right order. Each time an extra digit is added until they can't recall the correct order.
  • found the mean span for digits across all participants was 9.3 items. The mean span for letters was 7.3.
  • chunking= grouping sets of digits or letters into units or chunks. Miller made observations of everyday practice, noted that things come in 7- 7 days of the week.
  • thought the span of STM is about 7 items, plus or minus 2.
• duration

  = the length of time information can be held in memory.
• research-duration

  = Peterson+ Peterson tested students in 8 trials, each person was given a consonant syllable to remember, and also given a 3 digit number. The student counted backwards from the number until told to stop.

  -counting backwards= prevent any mental rehearsal of the consonant syllable.

  On each trial they were told to stop after varying periods of time.

  • findings= after 3 seconds, average recall was 80%, after 18 seconds it was 3%.
  • suggests STM duration may be about 18 seconds, unless we repeat the information over and over.
• research-duration of LTM

  = Bahrick studies participants aged between 17 and 74. High school yearbooks obtained.

  • recall tested by photo-recognition, and free recall where participants recall all the names of their graduating class.
  • findings= participants tested within 15 years of graduation were about 90% accurate in photo recognition. After 48 years, recall declined to about 70% for photo recognition. Free recall was less accurate than recognition- about 60% after 15 years, dropping to 30% after 48 years.
  • shows that LTM may last up to a lifetime for some material.
• Evaluation- coding

  separate memory stores:

  • strength= Baddeley's study is that it identified a clear difference between two memory stores.
  • later research showed that there is some exceptions to Baddeley's findings. But the idea that STM uses mostly acoustic coding and LTM mostly semantic has stood the test of time.
  • this was an important step in our understanding of the memory system, which led to the multi- store model.
• Evaluation-coding

  Artificial stimuli:

  • limitation= Baddeley's study used quite artificial stimuli rather than meaningful material.
  • eg: word lists had no personal meaning to participants. So Baddeley's findings may not tell us much about coding in different kinds of memory tasks, especially in everyday life
  • when processing more meaning information, people may use semantic coding even for STM tasks.
  • suggests the findings have limited application.
• Evaluation-capacity

  A valid study:

  strength= Jacob's study has been replicated.

  • the study is very old and early research often lacked adequate controls. eg: some participant's digit spans might have been underestimated because they were distracted during testing.
  • However Jacob's study has been replicated in better controlled studies- suggest Jacobs study is a valid test of digit span in STM.
• Evaluation- capacity

  Not so many chunks:

  • limitation= Miller's research may have overestimated STM capacity.
  • Cowan reviewed other research and concluded that the capacity of STM is only about 4.
  • this suggests that the lower end of Miller's estimate is more appropriate than 7 items.
• Evaluation- Duration

  Meaningless stimuli in STM study:

  • limitation= Peterson and Peterson's study, the stimulus material was artificial.
  • The study is not completely irrelevant because we do sometimes try to remember fairly meaningless material. Even so, recalling consonant syllables doesn't reflect most everyday memory activities where what we are trying to remember is meaningful.
  • so study lacked external validity.
• Evaluation- duration

  High external validity:

  • strength= Bahrick's study has high external validity.
  • researchers investigated meaningful memories. When studies on LTM were conducted with meaningless pictures to be remembered, recall rates were lower.
  • suggests that Bahrick's findings reflect a more real estimate of the duration of LTM.