The Nature of Memory: STM, LTM and Duration (Page 20)

Duration
1. LTM
  1. Duration
    1. LTM refers to memories that last anywhere from 2 hours to 100 years+
      1. i.e. anything that isn't short-term
    2. Example: Shepard 1967 - tested LTM duration
      1. Participants were shown 612 memorable pics, 1 at a time
        1 hour later - shown some of the pics among a set of new 1s
        Showed perfect regonition
        4 months later - still able to recognise 50% of the pics
    3. More 'real life' example: Bahrick et al 1975
      1. More 'real life' as the material to be remembered was more meaningful to the participants
      2. Participants (of various ages) were asked to put names to faces from their high school year book
        48 years on about 70% of people were accurate
2. STM
  1. Key Study - Peterson & Peterson 1959 (Landmark study)
    1. What did they do?
      1. Enlisted 24 students from their uni
      2. The experimenter said a 3 constant syllable (with no meaning) to the participant followed by a 3 digit number
        After hearing the syllable the participant had to count back from the number in 3s or 4s until told to stop + then asked to recall syllable
        Each participant was given 2 practice trials + 8 real trials
        On each trial the retention interval (time spent counting backwards) was different: 3,6,9,12,15,18 secs
        The reason for the counting was to prevent rehearsal
    2. What did they find?
      1. Participants remembered around 90% with 3 sec interval
      2. About 2% with 18 sec interval
      3. Results suggest - when rehearsal is prevented STM lasts about 20 secs at most
  2. Duration
    1. ST memories don't last long
    2. The info doesn't last very long + STM can't hold much info at a time
      1. Rehearsal is needed to keep the info in the STM (re-presenting the info to the STM)
        The result of the verbal rehearsal - the ST memories are held in the STM store + eventually become LT
3. How long a memory lasts
Evaluation
1. The duration of STM may be even shorter
  1. Peterson & Peterson findings have been challenged
    1. We may argue - the participants may have been relying on more than STM as they knew they knew they were going to be asked to recall the items after a distracting interval
    2. Marsh et al 1997
      1. Suggests - when participants do not expect to be tested after this interval, forgetting may occur after just 2 secs
        This suggests - our understanding of STM duration may not be as clear-cut as first thought
2. Not quite so short-term memory
  1. More recent research suggests that STM duration is not as short as Peterson & Peterson's study would suggest
    1. Nairne et al 1999
      1. Found - items could be recalled after as long as 96 secs
        In this study - participants were asked to recall the same items across trials - earlier studies items differed
      2. Suggests - info remains in STM for quite awhile unless it is replaced or overwritten
3. Peterson & Peterson validity
  1. 1 criticism of the study - only studying 1 type of memory - memory for syllables + digits, whereas much of the time our memories are concerned with other things, e.g what we did last night
  2. A 2nd criticism - Peterson & Peterson weren't actually testing duration. When the participants were counting backwards, the syllables could well have been displaced in STM by the digits - wiping out the memory for the syllables

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The Nature of Memory: STM, LTM and Duration (Page 20)

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