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Duration – STM & LTM

Duration – STM & LTM. Clearly, LTM can store information for a much longer time than LTM Some researchers have tried to measure their durations exactly: Peterson & Peterson (1959) – STM Bahrick et al (1975) – LTM These are key studies so make sure you learn APFCC. www.psychlotron.org.uk.

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Duration – STM & LTM

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  1. Duration – STM & LTM • Clearly, LTM can store information for a much longer time than LTM • Some researchers have tried to measure their durations exactly: • Peterson & Peterson (1959) – STM • Bahrick et al (1975) – LTM • These are key studies so make sure you learn APFCC www.psychlotron.org.uk

  2. Duration – STM • Peterson & Peterson (1959) • PPs presented with ‘trigrams’ (CVC nonsense syllables) and asked to recall them (accurately & in order) • Between exposure & recall there was a delay in which they did an interference task • The length of the delay was varied • Results obtained by plotting recall against length of delay www.psychlotron.org.uk

  3. Duration - STM % recall www.psychlotron.org.uk 3 6 9 12 15 18 Length of delay (s)

  4. Duration - STM • Recall declined steadily with time • After 3s 80% correct • After 6s less than 50% • After 18s less than 10% • Information is lost rapidly from STM, which seems to have a duration of about 20s if nothing is done to maintain the info (i.e. rehearsal) www.psychlotron.org.uk

  5. Duration - STM • The experiment lacked realism • Nonsense trigrams were used to eliminate the effect of meaningfulness • However, this is unlike the info that people typically deal with • The use of interference task is a problem • We cannot tell if the info decayed (as the Petersons claim) or was displaced by the task www.psychlotron.org.uk

  6. Duration - LTM • Bahrick et al (1975) • Test of VLTM using naturalistic materials • 392 US PPs who had left high school 1-48 years previously tested for recall of classmates • Free recall • Recognition of photos • Name recognition & photo matching www.psychlotron.org.uk

  7. Picture recognition Name recognition Free recall Duration - LTM % recall www.psychlotron.org.uk Years since leaving High School

  8. Duration - LTM • Recall was remarkably high • 80% accuracy for name recognition at 48yrs • 30% accuracy for free recall at 30yrs • Supports the idea that LTM can store some types of info for very long time • Free recall becomes more difficult over time, but recognition does not diminish much www.psychlotron.org.uk

  9. Duration - LTM • Ecological validity was high • The study used a naturally occurring form of info so avoided the artificiality often present in memory studies • The type of info used was very specific • Classmates may have high emotional significance, and there is usually great opportunity for rehearsal • Conclusions not generalisable to other types of information www.psychlotron.org.uk

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