Coding, capacity and duration of memory:

• What is your Short-term memory?

  The limited-capacity memory store. In STM, coding is mainly acoustic (sounds), capacity is between 5 and 9 items on average, duration is about 18 seconds
• What is your long-term memory?

  The permanent memory store. In LTM, coding is mainly semantic (meaning), it has unlimited capacity and can store memories for up to a lifetime.
• What is coding?

  The format in which information is stored in the various memory stores.
• What is capacity?

  The amount of information that can be stored in the various memory stores.
• What is duration?

  The length of time information that can be held in memory.
• Coding and Baddeley's procedure:

  Procedure:

  • present participants very rapidly with four conditions of words (acoustically similar and dissimilar, semantically similar and semantically dissimilar)
  • ppts serial recall the words immediately and after 20 minute break
• Coding and Baddeley's findings and conclusion:

  Findings:

  • immediate recall worse with acoustically similar words
  • After 20 minutes worse with semantically similar

  Conclusion:

  • coding in LTM is predominantly semantic
  • coding in STM is predominantly acoustic
• Coding- strength:

  P- One strength of Baddeley's study is that it identified a clear difference between two memory stores.

  E- Later research showed that there are some exceptions to Baddeley's. But the idea that STM uses mostly acoustic coding and LTM mostly semantic has stood the test of time.

  L- This was an important step in our understanding of the memory system, which led to the multi-store model
• Coding- limitation:

  P- One limitation of Baddeley's study was that it used artificial stimuli rather than meaningful material.

  E- For example, the word lists had no personal meaning to participants

  E- 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.

  L- This suggests that the findings from this study have limited application
• Capacity- Jacobs' procedure:

  Procedure:

  • Researcher reads out 4 digits and increases amount until ppts can no longer correctly recall
  • This is their digit span
• Capacity- Jacobs' findings and conclusion:

  Findings:

  • Mean digit span was 9.3 numbers and 7.3 letters

  Conclusion:

  • Miller- capacity of STM is 7+/-2 and chunking improves capacity
• Capacity- strength:

  P- One strength is that Jacobs' study has been replicated

  E- The study is a very old one and early research in psychology often lacked adequate controls. For example, some participants' digit spans might have been underestimated because they were distracted during testing

  E- Despite this, Jacobs' findings have been confirmed by other, better controlled studies since (e.g. Bopp and Verhaeghen)

  L- this suggests that Jacobs' study is a valid test of digit span in STM.
• Capacity- limitation:

  P- One limitation of Miller's research is that he may have overestimated STM capacity.

  E- Cowan reviewed other research and concluded that the capacity of STM is only about 4 (plus or minus 1) chunks

  L- This suggests that the lower end of Miller's estimate (five items) is more appropriate than seven items
• Duration of STM- Peterson and Peterson's procedure:

  Procedure:

  • Present ppts with a consonant trigram (YCS)
  • Ppts to count backwards from a three digit number for interval various seconds
  • Participants then asked to serial recall the trigrams
• Duration- Peterson and Peterson's findings and conclusions:

  Findings:

  • 80% correct recall after 3 second interval
  • 3% correct recall after 18 second interval

  Conclusion:

  • STM duration about 18 seconds unless we rehearse
• Duration of STM limitation:

  P- One limitation of Peterson and Peterson's study was that it used artificial stimuli rather than meaningful material

  E- The study is not completely irrelevant because we do sometimes try to remember fairly meaningless material

  E- Even so, recalling consonant syllables does not reflect most everyday memory activities where what we are trying to remember is meaningful.

  L- This means the study lacked external validity
• Duration of LTM- Bahrick's procedure:

  Procedure:

  • Tested 392 graduates (aged between 17 and 74) on their ability to:
  • recognise classmates pictures (from 50 photos)
  • match names to pictures
  • recall names with no pictured clue
• Duration of LTM- Bahrick's findings and conclusion:

  Findings:

  • Ppts performed very well up to 34 years since graduation, better on recognition than recall
  • Dip in performance after 47 years since graduation
  • 90% accurate in photo recognition after 15 years, 70% after 48 years
  • 60% accurate free recall after 15 years, 30% after 48

  Conclusion:

  • The duration of the LTM is very extensive
• Duration of LTM strength:

  P- One strength is that Bahrick's study has high external validity

  E- This is because the researchers investigated meaningful memories (i.e. of people's names and faces)

  E- When studies on LTM were conducted with meaningless pictures to be remembered, recall rates were lower

  L- This suggests that Bahrick's findings reflect a more real estimate of the duration of the LTM