coding+capacity+duration of memory

• Coding, Alan Baddeley

  • Definition = the form in which information is stored
  • Procedure:
  • 5 acoustically similar words (eg cat, can etc) or dissimilar (eg pit, cow etc)
  • 5 semantically similar words (eg large, big) or dissimilar (eg good, hot etc)
  • participants must recall
  • Findings:
  • Immediate recall = worse with acoustically similar words, STM codes acoustically
  • Recall after 20 minutes = worse with semantically words, LTM codes semantically
• strength for coding = Baddeley’s study identified 2 memory stores

  • Later research showed that there are exceptions to Baddeley’s findings
  • BUT the idea that STM is mostly acoustic and LTM is mostly semantic stayed the same
  • This led to the development of the multi-store model of memory
• limitation of coding = Baddeley’s study used artificial stimuli

  • The words used had no personal meaning to the participants so tells us little about coding for everyday memory tasks
  • When processing more meaningful information, people use semantic coding even for STM
  • Means the findings of this study have limited application
• capacity

  • Definition = amount/how much information can be stored
  • Joseph Jacobs = digit span
  • George Miller = span of memory/chunking
• Capacity, Joseph Jacobs

  • Procedure:
  • Researcher reads out four digits and increases until participant cannot recall the order correctly
  • Final number = digit span
  • Findings:
  • mean average to recall in correct order:
  • 9.3 numbers
  • 7.3 letters
• capacity, George Miller

  • Procedure:
  • Miller observed everyday practice and noted things that come in sevens
  • Eg = notes on music scale, days of the week, deadly sins
  • Findings:
  • The span of the STM is about 7 items (plus or minus 2)
  • Chunking can increase digit span = by grouping set of digits/letters into meaningful units
• strength for capacity = Jacob’s study has been replicated

  • This is an old study and may have lacked adequate controls (confounding variables, eg participants being distracted)
  • Despite this, Jacobs’ findings have been confirmed in later controlled studies (eg Bopp and Verhaeghen)
  • Shows that Jacobs’ study is a valid measure of STM digit span
• limitation of capacity = Miller may have overestimated STM capacity

  • Eg = Cowan reviewed other research
  • He concluded that the capacity of STM was only about 4 (plus or minus 1) chunks
  • Suggests that the lower end of Miller’s estimate (5 items) is more appropriate than 7 items
• duration

  • Definition = length/how long info can be stored for
  • Peterson and Peterson = STM
  • Bahrick et al = LTM
• Duration, Peterson and Peterson (STM)

  • Procedure:
  • 24 participants = gave participants random/meaningless consonants to recall
  • Then gave them numbers to stop maintenance rehearsal of consonants
  • Findings:
  • Average recall after 3 seconds = 80%
  • Average recall after 18 seconds = 3%
  • STM duration without rehearsal is up to 18 seconds
• Duration, Bahrick et al (LTM)

  • Procedure:
  • 392 Americans (aged 17-74), used high school yearbooks
  • Recall tested in 2 ways:
  • Photo recognition = 50 photos from yearbook
  • Free recall test = participants listed names of their graduating class
  • Findings:
  • Photo recognition:
  • After 15 years = 90% accurate
  • After 48 years = 70% accurate
  • Free recall:
  • After 15 years = 60% recall
  • After 48 years = 30% recall
• Limitation of duration = Peterson and Peterson’s study uses meaningless stimuli

  • We sometimes try to recall meaningless things so the study is not completely irrelevant
  • But recall of consonant syllables does not reflect meaningful everyday tasks
  • => the study lacked external validity
• strength of duration = Bahrick et al’s study high external validity

  • Everyday meaningful memories (eg of peoples faces and names) were studied
  • When lab studies were done with meaningless pictures to be remembered, recall rates were lower
  • Means that Bahrick et al’s findings reflect a more ‘real’ estimate of the duration of LTM
• Duration of sensory register (iconic), Sperling

  • Procedure:
  • Grid of digits and letters was quickly shown to participants (50 milliseconds)
  • condition 1 = recall whole grid
  • Condition 2 = recall the row that was indicated
  • Findings:
  • Whole grid = 42%
  • Individual row = 75%
  • Shows that information decays rapidly in the iconic sensory register