coding, capacity + duration

• coding:

  • format in which info is stored in various memory system
  • types: semantic, acoustic, visual
• baddeley coding:

  • gave participants 1 of 4 word lists to remember, then another set of words (acoustically similar, dissimilar, semantically similar, dissimilar)
  • shown original lists + asked to recall words in correct order immediately (STM) or after 20 mins (LTM)
• baddeley coding findings:

  • stm participants = worse performance on similar words - words became link + cant remember order (acoustic confusion)
  • ltm participants = worse performance on semantically similar - semantic confusion
  • conclusion = stm = acoustically similar, ltm = semantically similar
• EVALUATION: evidence for separate stores

  • later research = some exceptions to baddeley's findings e.g types of coding
  • stm = acoustic + vice versa has stood test of time
  • important step in understanding memory system - led to MSM
• EVALUATION: artificial stimuli

  • words in list have no personal meaning
  • findings may not tell us much about coding especially in daily life - processing = more meaningful, semantic may be used for stm
  • findings have limited application
• capacity:

  • amount of info that can be held in memory store
  • ltm capacity = unlimited
• Jacobs (STM capacity):

  • developed digit span technique to test capacity
  • shown series of numbers/letters + asked to recall immediately
  • series increased by 1 each time
• Jacob capacity findings:

  • average span for letters = 7.3, digits = 9.3 - miller called this 7 +- 2
  • applied to words as well (5-9 words = chunking)
• EVALUATION: high external validity

  • study is old + early research often lacked adequate controls - digit span underestimated due to distractions (CVs)
  • despite, findings confirmed by other controlled studies
  • study = valid test of digit span in STM
• EVALUATION: contradictory research (overestimation)

  • cowan - reviewed + concluded stm capacity = 4 +- 1 chunks
  • vogel et al - research on stm capacity of visual info shows 4 chunks = limit
  • lower end of estimate is more appropriate than 7
• peterson + peterson (STM duration):

  • 24 students
  • showed trigrams/ consonant syllables + recall after counting back in 3s
  • time delay differed with each trigram to test duration
• peterson + peterson findings:

  • when rehearsal prevented recall = 18s
  • after 3s = 80% recall
  • after 18s = 3% recall
• Bahrick et al:

  • 392 tested on memory of classmates
  • photo recognition + free recall
• bahrick et al findings:

  • 15 years after graduation = photo recognition 90% accuracy, free recall 60%
  • 48 years after graduation = photo recognition 70%, free recall 30%
• EVALUATION: high external validity (Bahrick)

  • investigated meaningful memories
  • other research with meaningless pictures = lower recall rates
  • findings reflect more real estimate of LTM duration
• EVALUATION: meaningless stimuli (peterson + peterson)

  • not completely irrelevant - sometimes try to remember meaningless info eg postcodes
  • recalling trigrams = doesnt reflect everyday memory activities that use meaningful memories
  • lacked ecological validity, not possible to generalise findings in real life