Coding, Capacity and Duration

Coding, Capacity and Duration

1. Baddeley (1966) Coding in STM & LTM

   • Tested participants with a list of either: acoustically similar/dissimilar, or semantically similar/dissimilar words
     • immediate recall: acoustically similar words were the worst, after 20 minutes: semantically dissimilar words were the worst.
       • STM is acousitc, LTM is semantic
         • Limitation: It didn't use meaningful material. The words had no personal meaning to the participants.
           • When processing meaningful information, people may use semantic coding even for STM tasks.
             • The results cannot be generalised to different kinds of memory task.

2. Miller (1956) Capacity of STM

   • He noticed that things come in sevens: there are 7 notes on the musical scale, 7 days of the week, 7 deadly sins etc.
     • The span of STM is about 7 items (plus or minus 2)
       • This can be improved by chunking
         • Limitation: May have overestimated the capacity of STM
           • Cowan (2001) reviewed other research & concluded that the capacity of STM was only about 4 items
             • This suggests that the lower end of Miller's estimate (5 items) was more accurate than 7 items

3. Peterson & Peterson (1959) Duration of STM

   • 24 students were given a 3 letter consonant syllable (e.g. YCG) to remember and a 3 digit number to count back from. They were given either 3,6,9,12,15 or 18 seconds.
     • On average, students recalled 80% of the syllables correctly after 3 seconds, and 3% of the syllables correctly after 18 seconds.
       • This suggests that the duration of STM is between 18-30 seconds
         • Limitation: Artificial stimulus. Trying to memorise consonant syllables does not reflect most real life memory activities where what we try to remember is meaningful
           • Study lacks external validity
             • But we sometimes try to remember fairly meaningless things such as phone numbers, so the study isn't completely irrelevant.