Short-term memory

Short-term memory

1. encoding- acoustic or visual

   • Baddeley (1966a and 1966b)
     • tested the effects of acoustic and semantic similarity in short and long-term memory
       • gave ppt lists of words acoustically similar or acoustically dissimilar
         • found that ppt had difficulty remembering acoustically similar words in STM but not in LTM
           • whereas semantically similar words posed little problem in short-term recall but led to muddled long-term memories

2. capacity- 7 +/- 2 units

   • George Miller (1956)
     • reviewed psychological research and concluded that the span of immediate memory is 7
       • people can cope reasonably well with counting seven dots flashed onto a screen
         • not many more than this
       • same is true if you are asked to recall musical notes, digits, letters and even words
     • found that people can recall 5 words as well as they can recall five letters
       • we chunk things together in order to remember more
   • London school teacher- Joseph Jacobs
     • used digit span technique
       • average span for digits was 9.3 items
       • average span for letters was 7.3 letters
   • Simon (1974)
     • people have a shorter memory span for larger chunks

3. duration- measured in seconds and minutes

   • Peterson and Peterson (1959)
     • conducted landmark study on the duration of STM
       • enlisted help of 24 students attending their university
     • experimenter said a consonant syllable to ppt followed by 3 digit number (i.e. WRT 303)
       • consonant syllable was selected to have no meaning
       • immediately after hearing syllable and number, ppt had to count backwards in 3s or 4s until told to stop
         • the ppt asked to recall the nonsense syllable
           • each ppt given 2 practise trials followed by 8 trials
             • on each trial the retention interval (time spent counting backwards) was different
         • stopped rehearsal that could aid recall
     • found that ppt remembered about 90% when there was only a 3 second interval and about 2% when the interval was 18 seconds
       • suggesting that when rehearsal is prevented, STM lasts about 20 seconds at most