Duration of Memory

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  • Duration
    • Long Term Memory (LTM)
      • LTMs can last anywhere from 2 hours to 100 years, potentially unlimited.They are any memory that isn't short term.
      • Studies
        • Shepard (1967) - Showed pps 612 memorable pictures one at a time. After an hour they were again showed these pictures amongst other pictures and there was almost perfect recognition. 4 months later they could still remember the images.
        • Bahrick et al (1975) - Asked people of various ages to put names to faces in their high school yearbook. After 48 years, there was 70% accuracy
          • The material being remembered was more meaningful to the pps and so the duration of the LTM was higher
    • Short Term Memory (STM)
      • STMs last for a very short period of time. Rehearsal keeps the memory active in STM and this verbal rehearsal eventually makes STMs transfer to LTM
      • Studies
        • Peterson & Peterson (1959) - Performed on 24 students from their university. The experimenter said a consonant syllable to the pp followed by a 3 digit number (e.g WRT 303) This syllable was selected so it was sure there would be no meaning (e.g BCB rather than BBC.)
          • After hearing the syllable, the pps had to count backwards from the number in 3s or 4s until told to stop, then they had to recall the nonsense syllable. The pps counted backwards to stop rehearsal of the syllable.
            • There were 8 trials in total, 2 practice and 6 real. In each trial, the time spent counting backwards varied: 3, 6, 9, 12, 15, 18
            • Found that pp recall was 90% on 3 second intervals, but 2% during 18 sec intervals.
              • This supports the idea that rehearsal plays an important part in STM, prevention of rehearsal causes STM to last for 20 secs at most
                • Evaluation
                  • Duration may be shorter
                    • Nairne et al (1999) - found that items could be recalled after as long as 96 secs. Pps were asked to recall the same items across trials (in original study different items were used, leading to interference between items, decreasing recall)
                      • This research supports the idea that information remains in STM for quite a while until other material replaces / overwrites it
                  • Duration may be longer
                    • Pps may have been relying on more than STM alone because they knew that they were going to be asked to recall the items after the interval with the distraction.
                      • Marsh et al (1997) -  Suggests that if pps do not expect to be tested after the interval, forgetting may occur in under 2 secs.
          • Validity
            • This study only focuses on one type of memory (syllables and words), whereas many other items can enter STM. It is not generalisable to all memories
            • Displacement rather than duration may have been tested. During the interval, the syllable may have been displaced by the numbers.
    • This is how long a memory lasts until it is not available to recall anymore

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