Coding, capacity and duration

• Baddeley conducted research on coding by giving four groups lists of words to remember and then asked them to recall them.
• Baddeley’s four groups were:

  • words that sounded similar
  • words that sounded different
  • words with similar meanings
  • words with different meanings
• Research on coding:

  When participants were asked to recall the list of words immediately from short-term memory, they tended to do worse with acoustically similar words.
• Research on coding:

  When the participants were asked to recall the list of words after 20 minutes from long-term memory, they tended to do worse with semantically similar words.
• Evaluation of coding research:

  Baddeley identified a clear difference between two memory stores and found that STM uses acoustic coding and LTM uses semantic.
• Evaluation of coding research:

  Baddeley used an artificial stimuli rather than meaningful material, so we cannot generalise to everyday life when we process more meaningful information. Therefore this study may have limited application.
• Research on capacity:

  Jacobs found that the mean span of digits participants could remember was 9.3 and the mean span for letters was 7.3.
• Research on capacity:

  Miller found that the capacity of STM is 7 items plus of minus 2 (5-9).

  He also found that chunking can help us remember information by grouping digits/letters into chunks.
• Evaluation of capacity research:

  Jacob’s study is a valid test of digit span in STM as his study has been successfully replicated.
• Evaluation of Miller’s research:

  Miller may have overestimated STM capacity. Cowan concluded that the capacity of STM is only about 4 items plus or minus 1.
• Duration of STM:

  Peterson and Peterson asked 24 students to remember a consonant syllable while counting backwards to prevent mental rehearsal. After 3 seconds, recall was 80%. After 18 seconds, it was about 3%. They concluded that the duration of STM is about 18 seconds.
• Evaluation of Peterson&Peterson:

  They used an artificial stimulus so the study lacks external validity.
• Duration of LTM:

  Bahrick studied 392 participants aged 17-74 and asked them to recall the names of people from their high school yearbooks.
• Bahrick found that within 15 years of graduation recall was 90% accurate for photo recognition and 60% accurate for free recall. After 48 years, recall declined to 70% for photo recognition and 30% for free recall.
• Evaluation of Bahrick:

  Researchers used meaningful memories so has high external validity.