Duration of STM

• what does the STM allow us to do?

  retain information long enough to use it

  (eg we should be able to look up a phone number and remember it for long enough to dial it)

  the coding is mainly VISUAL AND ACOUSTIC
• What is the coding of the stm?

  mainly visual and acoustic
• What did Peterson and Peterson's 1959 do?

  Trigram Retention Experiment
• what did the "Trigram Retention Experiment" demonstrate?

  that STM lasts approximately BETWEEN 15 AND 30 SECONDS
• how was "Trigram Retention Experiment" carried out?

  Here pps were read a nonsense trigram

  Immediately after this the pps had to count backwards in threes starting from a very large number eg 587

  This time period was called the RETENTION INTERVAL and varied from 3-18 seconds and this counting backwards task was the DISTRACTER TASK (designed to stop rehearsal of the trigrams)
• what were the nonsense trigrams?

  three consonants that have no meaning eg JTV
• Give criteria for the trigrams used in "Trigram Retention Experiment" ?

  • no vowels - vowels make sounds and words
  • no words eg CAT
  • no acronyms eg USA
  • no sequences eg ABC
• what happened with acoustically similar words ("Trigram Retention Experiment" ?)?

  creates acoustic confusion

  cannot separate words

  therefore recall is poor

  conclude - we must need acoustic coding in STM
• What was aim of "Trigram Retention Experiment" ?

  to find out what the duration of STM is
• what was method of "Trigram Retention Experiment" ?

  Pps were shown a trigram and asked to recall it after varying times

  In between seeing the trigram and recalling it, the pp did a DISTRACTION TASK to prevent them from rehearsing it and moving it to LTM

  This involved counting backwards in threes
• what were the results of "Trigram Retention Experiment" ?

  90% recall after only 3 seconds

  The recall reduced with time until only 6% after 18 seconds
• what was the conclusion from the "Trigram Retention Experiment" ?

  If rehearsal is prevented then the information vanishes from STM after only a few seconds
• what was the evaluation of the "Trigram Retention Experiment" ?

  poor ecological validity since trigrams are an artificial thing to remember
• why did "Trigram Retention Experiment" have poor ecological validity?

  because trigrams are an artificial thing to remember