Memory

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Jacobs-Key study into capacity of STM

Procedures

  • Read out a list of either letters or numbers & pts would recall them
  • Lists increased in length until pts could successfully recall them 50% of the time

Findings

  • STM capacuty for digits was 9 whereas letters was 7
  • STM increased with age, 8 year olds recalled 7 digits whereas 19 year olds recalled 9 digits

Conclusions

  • STM has limited capacity between 5-9 digits & age affects it since people may improve recall strategies with age

Strengths 

  • Findings have been replicated by Miller who coined the phrase "the magic number 7+/-2" to descrive the capacity 

Limitations

  • Age & practise have been shown to influencecapacity and nowadays STM limitations are often viewed as due to processing limitationS associated with attention
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Bahrick High School Yearbooks-Nature of LTM

Procedures

  • 392 USA ex-high-school students,17-74 
  • tested in free recall (list names of all people in their graduating class), face recognition (identify classmates from 50 photos) & name recognition test (ex-school friends)

Findings

  • Free recall tested within 15 years of graduation=60% 48 years=30%
  • Face recognition: 15 years=90% 48 years=40%
  • Name recognition 15 years=90% 48 years=80%

Conclusions

  • Evidence VLTM lasts upto 57 years after graduation
  • Some loss of memory over time 
  • Recognition better than recall, suggesting in real life our memories contain a vast amount of information but we sometimes need a cue to access it.
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Bahrick High School Yearbooks-Nature of LTM

Strengths

  • Compared to most research, usually carried out in a lab, Bahricks has high mundane realsim
  • Asking pts to recall thier classmates tests real life memory
  • Research is more representative of natural behaviour and has high ecological validity
  • Can generalise to other findings

Limitations

  • Recall m ay have been better in the setting because of rehearsal
  • Pts may have seen ex class mates regularly
  • Researchers asked pts how often then had met up with their ex class mates and looked at their year books. They found that this was more common with recent graduates but became less the longer it was since the pts graduated 
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Peterson & Peterson Trigrams- Duration of STM

Procedures

  • Pts read a nonsense trigram which was three constanants with no meaning e.g. LBT 
  • After pts had to count backwards in threes starting from a large 3 digit number e.g. 657 for a specific time
  • Time period was called retention period and varied from 3 to 18 seconds

Findings

  • After 3 second retention time, approx 90% of the trigrams were recalled correctly
  • After 6 seconds-50%
  • After 18 seconds-6%

Conclusions

  • Duration of STM is approx 20 seconds
  • Information is held in STM and quickly lost without rehearsal
  • STM is distinct from LTM because the duration of STM is much greater
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Peterson & Peterson Trigrams- Duration of STM

Strengths

  • Highly contolled lab experiment
  • IV under experimenters manipulation
  • Impact of confounding variables reduced
  • Cause and effect can be inferred 
  • Can be said time delay causes recall to decline

Limitations

  • Lacks mundane realsim
  • Trigrams are not representative of everyday memory demands
  • Artificiality of task may bias the results
  • Trigrams may be remembered less than meaningful information
  • Duration of STM may be longer for more everyday memory
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Baddeley-Encoding in STM

Procedures

  • Pts presented with 4 word list
  • A-Acoustically similar words
  • B-Acousticall dissimilar words
  • C-Semantically similar words
  • D-Semantically dissmilar words
  • 75 Pts heard one list repeated four times
  • Immediately after they were given a list that contained all the original words but in the wrong order
  • Task was to rearrange the words in correct order

Findings

  • Pts given list A performed worst

Conclusions

  • Since list A was recalled least efficiently, it would appear that theres acoustic confusion in STM. Therefore it tends to be encoded acoustically
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Baddeley-Encoding in STM

Strength

  • Results make cognitive sense

Limitation

  • STM is not restricted to acousite encoding 
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