Compare Duration in STM and LTM.

• STM - AO1


  Has a duration of 18 – 30s if the information is not rehearsed.

  • Peterson and Peterson. 24 undergraduates, 8 trials. Given a nonsense trigram to remember (e.g. ZFB) and had to count backwards in threes from a large three-digit number (to prevent rehearsal).
  • On each trial they were told to stop counting backwards after a different amount of time (called a retention interval) 3,6,9,12,15 or 18 seconds. After 3 seconds about 80% of trigrams were recalled correctly.After 18 seconds average recall fell to about 3%. 

  The STM memory fades/decays under 30 seconds without rehearsal. 
• LTM -AO1


  Has unlimited.

  • Bahrick 392 American pps.  High school yearbooks obtained. 
  • Recall tested in various ways including. 
  • Photo-recognition test consisting of 50 photos, some from the pps’ yearbook. 
  • Free recall test, pps listed all the names of their graduating class.
  • 15 years after 90% accurate in photo-recognition.
  • 48 years after graduation recall was about 70% accurate in photo-recognition. 
  • Free recall was less accurate (60% then dropping to 30%).