Coding, capacity & duration

• Short-term memory: The limited capacity store, coding is mainly acoustic, capacity between 5 to 9 items, duration around 18 seconds.
• Long-term memory: The permanent memory store, coding is mainly sematic, unlimited capacity, last a lifetime.
• Coding: The format in which information is stored in various memory stores.
• Capacity: Amount of information that can be held in a memory store.
• Duration: The length of time information can be held in a memory store.
• Research on coding, Alan Baddely:

  He gave a list of words to 4 groups of participants to remember-

  • Group 1 (acoustically similar): Words that sound the same.
  • Group 2 (acoustically dissimilar): Words that sound different.
  • Group 3 (Semantically similar): Words with similar meaning.
  • Group 4 (semantically dissimilar): Words with different meaning.
• Research on coding, Alan Baddely:

  • When asked to recall words immediately (STM), the participants did worse with the acoustically similar words.
  • When asked to recall after 20 mins (LTM), the participants did worse with the semantically similar words.
  • Shows STM coding is acoustic, LTM is semantic.
• Research on coding (Strength):

  • Separate memory stores- Identified clear difference between two memory stores, finding have stood the test of time, led to multi-store model.
• Research on coding (Limitation):

  • Artificial stimuli- Didn't use meaningful material, doesn't tell us about coding in everyday life, people may code semantically in STM is information has meaning.
• Research on capacity, Jacobs:

  • Read out 4 digits and had participants recall info.
  • If this was correct he added another digit and so on until they no longer could.
• Research on capacity, Jacobs:

  • The mean span was 9.3 digits which means that's the average someone can hold.
• Research on capacity (Strength):

  • Valid study: Jacobs study has been replicated and the results have been confirmed.
• Research on capacity, George Miller:

  • Made observations of everyday practice.
  • Noted many things come in 7.
  • People can recall words better then letters due to chunking.
  • Believed the span of the STM was 7.
• Research on capacity (Limitation):

  • Not so many chunks- Miller may have over estimated STM capacity, other research shows it may only be 4 chunks.
• Research on duration, Peterson & Peterson:

  • Gave each participant a constant syllable such as YCG to remember.
  • They also got given a 3 digit number to count back from to prevent rehearsal.
  • They were told to stop after a certain time.
  • Found after 3 seconds active recall was about 80%, after 18 seconds it was around 3%.
  • Suggests STM is about 18 seconds unless rehearsal takes place.
• Research on duration, Bahrick:

  • Obtained yearbooks of participants aged 17 to 74.
  • Tried to see how many faces people could remember.
  • 90% accuracy when tested within 15 years of graduation, declined to 70% after 48 years (photo recognition).
  • 60% accuracy after 15 years, declined to 30% after 48 years (free recall).
  • Shows LTM may last a lifetime.
• Research on duration (strength):

  • High external validity- Bahrick investigated meaningful memories which shows a more real estimate for duration of LTM.
• Research on duration (limitation):

  • Meaningless stimuli- Peterson & Peterson used artificial stimuli which doesn't reflect real life so study lacks external validity.