Coding Capacity Duration of Memory

• What is the research into STM coding?

  • Baddeley gave different lists of words to groups of PPs to remember: acoustically similar, acoustically dissimilar, semantically similar semantically dissimilar
  • Baddeley found that PPs found the acoustically similar words most difficult to recall immediately
  • Shows that STM is acoustically coded
• What is the research into LTM coding?

  • Baddeley gave different lists of words to 4 groups of PPs to remember: acoustically similar, acoustically dissimilar, semantically similar semantically dissimilar
  • Baddeley found that PPs found the semantically similar words most difficult to recall 20 mins later
  • Shows that LTM is semantically coded (have the most confusion recalling semantically similar words show you are focusing on these words)
• What is the research into STM duration?

  • Peterson and Peterson used trigrams that PPs had to remember while giving them a 3 digit number they had to count backwards from
  • This was to prevent rehearsal
  • They did this 8 times and increased the time in which PPs were told to stop counting backwards
  • They then concluded from this that STM duration is 18-30
• What is the research into STM capacity?

  • Jacobs did a digit span test where PPs had to recall numbers and the amount of numbers gradually increased until they made a mistake
  • Jacobs found the mean capacity for letters was 7.3 and for numbers was 9.3
  • STM capacity is 7 plus or minus 2
• What research did Peterson and Peterson discover?

  • Researched duration of STM
  • Used consonant syllables such as BNT in their research
  • Used counting backwards as a means of preventing rehearsal
  • Found that STM lasts about 18-30 seconds
• What research did Miller discover?

  • Researched capacity of STM
  • Used the term 'the magical number 7' to describe capacity of STM
  • Did similar research to Jacobs (digit span test)
  • Investigated chunking in STM and suggested we can recall more than 7 words this way
• Research into the duration of LTM: Bahrick

  • Studied 392 American PPs aged 17-74
  • Participants asked to recognise faces and recall names from their yearbook
  • 15 years after graduation face recognition was 90% accurate and name recall was 60% accurate
  • 48 years after graduation, face recognition was 70% accurate and name recall was 30% accurate
  • Concluded that LTM has an unlimited duration
• AO3 STM Coding: Separate Memory Stores

  • Baddeley’s study identified a clear difference between two memory stores
  • Later research showed that there are some exceptions to Baddeley’s findings
  • But the idea that STM uses mostly acoustic coding and LTM mostly semantic has stood the test of time
  • This was an important step in our understanding of the memory system which led to the multi-store model
• AO3 STM Coding: Artificial Stimuli

  • Baddeley’s study used artificial stimuli rather than meaningful material
  • The word lists had no personal meaning to participants
  • So Baddeley’s findings may not tell us much about coding in different kinds of memory tasks especially in everyday life
  • When processing more meaningful information people may use semantic coding even for STM tasks
  • The findings from this study have limited application
• AO3 STM Capacity: Valid Study

  • Jacobs’ study has been replicated
  • The study is very old and early research in psychology lacked adequate controls
  • Some participants’ digit spans might have been underestimated because they were distracted during testing (confounding variable)
  • Despite this Jacobs’ findings have been confirmed by better controlled studies
  • This suggests that Jacobs’ study is a valid test of digit span in STM
• AO3 STM Capacity: Not so many chunks

  • One limitation of Miller’s research is that he may have overestimated STM capacity
  • Research concluded that the capacity of STM is only about 4 (plus or minus 1) chunks
  • This suggests that the lower end of Miller’s estimate (5 items) is more appropriate than 7 items
• AO3 STM Duration: Meaningless stimuli

  • One limitation of Peterson and Peterson’s study is that the stimulus material was artificial
  • The study is not completely irrelevant because we do sometimes try to remember fairly meaningless material e.g. phone numbers
  • Recalling consonant syllables does not reflect everyday memory activities where what we try to remember is meaningful
  • This means the study lacked external validity
• AO3 LTM Duration: High external validity

  • Bahrick’s study has high external validity
  • The researchers investigated meaningful memories (people’s names and faces)
  • When studies on LTM were conducted with meaningless pictures to be remembered recall rates were lower
  • This suggests that Bahrick et al.’s findings reflect a more ‘real’ estimate of the duration of LTM