Duration of Memory

• Duration of STM

  Peterson tested 24 students in eight trials each. On each trial the student was given a consonant syllable (YCG) to remember. They were also given a 3 digit number. The student counted backwards from the number until told to stop. This was to prevent any mental rehearsal of the syllable. On each trial they were told to stop after varying periods of time: 3, 6, 9, 12, 15 or 18 seconds-the retention interval.
• Peterson found that after 5 seconds the average recall was about 80%, after 18 seconds it was about 3%. Peterson's study findings suggested that STM duration may be about 18 seconds, unless we practice verbal rehearsal.
• Duration of LTM

  Bahrick studied 392 American participants aged 17 - 74. Highschool yearbooks were obtained from the participants or directly from some schools. Recall was tested in various ways including (1) photo recognition test consisting of 50 photos, some from the participants high school yearbooks. (2) free recall test where participants recalled all the names of their graduating class.
• In Bahrick’s study participants tested within 15 years of graduation were 80% accurate in photo recognition photos, after 48 years of graduation, recall declined to 70% for photo recognition. Free recall was less accurate overall, 60%. after Is years and 30% after 48 years. This shows that LTM may last up to a lifetime for some matenal.