1. Coding, capacity, duration

• Define coding

  • The process of converting information between different forms
• Baddely - research on coding

  • Group 1 - acoustically similar eg. cat, cab, can
  • Group 2 - acoustically dissimilar eg. pit, few, cow
  • Group 3 - semantically similar eg. great, large, big
  • Group 4 - semantically dissimilar eg. words with different meanings
  • Pps were shown the original words and asked to recall them in the correct order. When they did this task immediately recalling from STM, they did worse with acoustically similar words
  • Recalling after 20 minutes with LTM, pps did worse with semantically similar words
  • Info in STM - coded acoustically
  • Info in LTM - coded semantically
• Research on capacity

  • Jacobs found out how much info STM can hold at one time by measuring digit span
  • A researcher reads out a number of digits until a person can no longer recall them eg. 4 digits, then 5, then 6
  • Miller - proposed the theory of chunking. He noted that things come in sevens and thought that the span of STM is about seven items, plus or minus two.
  • He also noted that people can recall five words as easily as five letters - we do this by chunking
• STM duration - Peterson and Peterson

  • 24 students in 8 trials each
  • Each trial, the student was given a consonant syllable to remember with a 3 digit number
  • They counted backwards from this number until told to stop to prevent mental rehearsal of the consonant syllable
  • On each trial they were told to stop after varying periods of time
  • Findings show that STM duration may be about 18 seconds
• LTM duration - Bahrick

  • 392 American pps aged 17-74
  • Recall was tested through highschool yearbooks through photo recognition of 50 photos and free recall of names
  • Pps tested within 15 years of graduation were 90% accurate with photo recall
  • After 48 years, recall declined to 70%
  • Free recall less accurate than photo recognition
  • This shows that LTM may last up to a lifetime for some material
• Strength - Baddely's study on coding

  • A clear difference between two memory stores - STM and LTM
  • His research established that STM and LTM were separate stores due to information being coded differently - acoustically and semantically
  • This difference was made apparent when pps struggled to remember acoustically similar words immediately after recall and had difficulty remembering semantically similar words 20 minutes later
  • Step towards understanding the memory system which led to the MSM
• Limitation - Baddely's study on coding

  • Artificial stimuli used as opposed to meaningful material
  • Acoustically similar words such as bat and cat have no significant meaning to pps
  • This means words will be harder to remember - important and more meaningful material such as names would be better instead
  • Furthermore, the lab setting environment decreases external validity as well as limiting ecological validity
  • Thus findings from Baddely's study are somewhat limited in application
• Strength - Jacob's study on capacity

  • Successfully replicated through the understanding of digit span
  • Although this study was an old one which may have lacked adequate controls eg. low internal validity and confounding variables
  • Despite this his findings have been confirmed by Bopp and Verhaeghen through a controlled study
  • Suggests Jacob's study is a valid test of digit span in STM
• Limitation - Miller's study on capacity chunking

  • Capacity of STM may have been innacurate and overestimated
  • Cowan - reviewed other research and concluded that the capacity of STM is only about 4 +/- 1 chunks
  • This contradictory research has led to a review of the capacity of STM
  • This suggests that the lower end of Miller's estimate (5 items) is more appropriate than seven items
• Strength - Bahrick's study on LTM duration

  • High external validity
  • Due to researchers investigating meaningful memories - peoples names and faces
  • Shepard - conducted a study on LTM with meaningless pictures to be remembered, recall rates were lower
  • This suggests Bahrick et al.'s findings reflect a more real estimate
• Limitation - Peterson and Peterson study on STM duration

  • Artificial stimulus material
  • Pps asked trigrams that would not be encountered in real life
  • The recalling of consonant syllables does not reflect mundane realism and is not considered to be a meaningful test of memory
  • This means the study lacks external validity