The nature of memory: STM, LTM & Duration

The nature of memory: STM, LTM & Duration

1. Duration

   • STM
     • Doesn't last very long
     • Example
       • Remembering 7 digit phone no
         • Maintained in STM via repetition
           • Fades when convo starts
     • Rehearsal
       • Repetition to keep re-presenting to STM
       • Keeps memory active
       • Result of verbal rehearsal
         • STM held in STM store and eventually become LT
     • Lloyd & Margaret Peterson (1959)
       • Landmark study of duration of STM
       • 24 Students attending uni
       • Experimenter says consonant syllable
         • Followed by 3-digit no (e.g. WRT 303)
         • Selected to have no meaning
           • 'BBC' meaningful
         • Immediately after hearing syllable & no
           • Count backwards in 3s /4s until told to stop
             • Interference to stop rehearsal
           • After - ppts recall nonsense syllable
             • Each ppt given 2 practice trials
               • Each trial, retention interval (time spent counting backwards) different - 3, 6, 9, 12, 15,& 18 secs
       • Ppts remembered about 90% - 3 sec interval
         • 2% remembered - 18 sec interval
         • When rehearsal prevented STM lasts about 20 mins at most
   • LTM
     • 2 hours to 100 years
       • Anything that isn't short term
         • Some are long lasting
     • Shepard (1967)
       • Showed ppts 612 memorable pics, one at a time
         • Hour later
           • Shown some of these pics among others
             • Almost perfect recognition
         • 4 months later
           • Still able to recognise 50% of pics
     • Bahrick et al (1975)
       • Ask people of various ages
         • Put names to faces from high school year book
           • 48 years later
             • 75% Accuracy

2. Evaluation

   • Duration of STM may be shorter
     • Peterson & Peterson
       • Findings been challenged
         • Argue
           • Ppts relying on more than STM alone
             • Knew they were going to recall items after interval
     • Other research (e.g. Marsh et al)
       • Suggested - ppts do not expect to be tested after this interval
         • Forgetting may occur after just 2 secs
       • Suggests - our understanding of duration of STM may not be as clear-cut as once thought
   • Not quite so STM
     • More recent research
       • Suggests - duration of STM
         • Not as short as Peterson & Peterson study suggests
       • Naime et al (1999)
         • Found - items could be recalled after as long as 96 secs
           • Seems, that info remains in STM
             • Quite a while unless other material replaces / overwrites it
         • Ppts asked to recall same items actross trials
           • Other studies, different items used on each trials
             • Led to interference between items, decreasing recall
   • Validity
     • Criticism of Peterson & Peterson
       • Psychologists only studying 1 kind of memory
         • For syllables & words
         • Much of time our memories concerned w/ other things
           • E.g what happened last night, what my children look like
           • Times when remembering words
             • E.g. Ordering drinks, remembering someones phone no
       • Another critism
         • Peterson & Peterson not actually testing duration
           • When Ppts counting backwards
             • Nonsense syllable could've been displaced in STM
               • By nos, wiping out memory for syllables