coding capacity & duration of memory

coding capacity & duration of memory

1. research on coding

   • stored in different formats
     • converting info from one format to another = coding
   • Baddeley
     • different lists of words for people to remember
       • acoustically similar
         • cat
         • cab
         • can
       • acoustically different
         • pit
         • few
       • semantically similar
         • great
         • big
         • large
       • semantically different
         • good
         • huge
         • hot
     • shown the words had to say them in the right order
       • immediately after = stm
         • worse with acoustically similar
       • after 20 minutes = ltm
         • worse in semantically similar

2. research on capacity

   • digit span
     • how much can stm hold
       • Jacobs
         • 4 digits recall in order
           • if correct move to 5 digits etc..
             • mean = 9.3 items
               • mean for letters = 7.3
   • span of memory & chunking
     • Miller
       • things come in sevens
         • 7 notes in a scale
         • 7 days in a week
         • 7 deadly sins
       • span of stm = 7 + - 2
       • people can remember 5 words as well as letters
         • they do this by chunking
           • grouping digits or letters together

3. research on duration

   • duration of stm
     • Peterson
       • 24 undergraduate students
         • 8 trials
           • each trial = consonant syllable e.g. YCG and a 3 digit number to remember
             • then count backwards from that number until told to stop
               • prevent mental rehearsal of letters
               • told to stop after 3 6 9 12 15 or 18 seconds (retention interval)
       • results
         • stm very short duration unless rehearsed
   • duration of ltm
     • Bahrick
       • 392 American participants 17 - 74
         • 2 conditions
           • photo recognition - 50 photos from yearbook
           • free recall - name as many people as they could remember
       • results
         • under 15 years of graduation
           • 90% accurate photo recognition
           • 60% free recall
         • after 48 years
           • 70% photo recognition
           • 30% free recall
         • ltm lasts for a long time

4. evaluation - coding

   • artificial stimuli
     • word list - no personal meaning
       • can we really generalise it

5. evaluation - capacity

   • lacking validity
     • long time ago
       • not much control of variables
         • participants may have been distracted
         • however there has been research to support it
   • not so many chunks
     • Miller overestimated the capacity of stm
       • Cowan reviewed other research
         • found capacity about 4 chunks

6. evaluation - duration

   • meaningless stimuli - Peterson
     • stimulus artificial
       • doesn't reflect real life
         • lacked external validity
           • however some things like phone numbers may be meaningless
   • higher external validity - Bahrick
     • real life meaningful memories
       • confounding variables...
         • the people had probably checked their yearbook since graduation

7. evaluation +

   • criticising Peterson
     • one reason why we forget things in stm is memory trace
       • it disappears if not rehearsed
         • Peterson = participants counted down - displaced other info
     • or the info is displaced
       • limited capacity and new info will push old out