coding, capacity and duration

• Human memory can most broadly be defined as the process by which we retain information about events that have happened in the past.
• Short-term memory is a limited capacity memory store, where as long-term memory is a permanent memory store.
• Capacity – the amount of information  held in a memory store
• Duration – The length of time information can be held in the memory
• Coding – the format in which information is stored in various memory stores.
• Millers magic number:

  Miller conducted similar experiments and concluded that on average, we can recall 7 plus or minus 2 items (5-9)

  Miller also found that we can remember 5 words just as easily as we can remember 5 letters. We do this by chunking
• Peterson and Peterson:

  Had 24 pps recall trigrams (3 syllables) e.g. TGH, CLS.

  They were presented 1 at a time and were recalled in intervals of 3, 6, 9, 12, 15, 18 seconds

  During the interval pps were asked to count backwards in threes so that they could not rehearse the trigrams.

  Found STM has a limited duration of around 18 secs
• Jacobs measured the digit span of pps (the largest amount of numbers a pp can remember) and found the mean digit span was 9.3 items (for letters 7.3)
• Bahrick:

  Showed US graduates their high-school yearbooks and asked them to name the students.

  • 90% correctly matched names and faces after 14 years
  • 60% correctly matched names and faces after 47 years

  Concluded people can remember certain types of info for almost a lifetime (unlimited)
• Baddley:

  Gave different lists of words to pps to recall

  1. Acoustically similar words e.g. cat, mat, bat
  2. Acoustically dissimilar words e.g. pit, few, cow
  3. Semantically similar e.g. big, large, huge
  4. Semantically dissimilar e.g. huge, hot, ball

  Found more mistakes were made with acoustically similar words straight after learning them and with semantically similar words 20 mins after learning (LTM)

  Suggests STM is coded acoustically and LTM is coded semantically
• 1. 7 +- 2
  2. 18 seconds
  3. acoustic
  4. unlimited
  5. unlimited
  6. semantic

  
• weakness -

  Much of this research lacked standardisation and scientific methods due to the time that they were conducted in, particularly Jacobs digit span tests.

  This reduces the validity and reliability of the results
• strength -

  Bahricks research used meaningful stimuli as he used real names and faces from the pps past and reflect items that would be stored in our LTM in real life.

  Bahrick’s study has high external validity and the findings reflect a more ‘real’ estimate of LTM and can therefore be generalised to daily life.
• weakness -

  Some studies into memory fail to reflect real life situations e.g. Miller and Peterson, as they use artificial stimuli which have little personal meaning to pps.

  This limits the generalisability of findings to real life and lowers ecological validity.
• weakness -

  Recent research suggests Miller over-estimated the capacity of STM and argues it is more likely to be 4 items, not 5-9.

  This may reflects the outdated methodologies used by Miller and the lack of control, and suggests a slightly lower capacity of STM