Duration STM, LTM

Duration STM, LTM

1. short term memory doesn't last very long

   • the way most people keep information in their STM for more than a few seconds is to rehearse it and eventuallty becomes long term

2. studies into duration of LTM

   • Shepard 1967
     • showed participants 612 memorable pictures, one at a time - hour later they were shown some of the pictures with others and showed almost perfect recognition
       • 4 months later - still able to recognise 50% of photos
   • Bahrick et al 1974
     • 392 american high school students tested in 4 ways:
       • free recall of names of ex-classmates, photo recognition test - 50 photos, name recognition and name and photo matching test
         • 90% accuracy with face and name recognition even those who had left high school 34 years ago - this dropped to 80% after 48 years for name recognition and 40% after 48 years for face recogniton - free recall- less accurate - 60% after 15 years and 30% after 48 years
           • conclu: recognition better than recall, classmates rarely forgotton once recognition cues had been given

3. studies into duration of STM

   • Peterson and Peterson 1959
     • 24 participants had to recall triagrams - to prevent rehearsal - had to count backwards in threes or fours from a specified random number until they saw a red light appear
       • were asked to recall trigrams after intverals of 3,6,9,12,15 or 18 seconds
         • longer the delay = less trigrams recalled - were able to recall 80% trigrams after 3 seconds, after 18 seconds less than 10% trigrams recalled
           • shows STM has limited duration when rehearsal is prevented. Results show that STM differs from LTM in terms of duration - supports multi store model of memory

4. duration = a measure of how long memory lasts before it is no longer avaliable