Coding, capacity and duration: key studies

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  • Coding, capacity and duration: key studies
    • Coding
      • Joseph Jacobs (1887)
        • created a technique to measure digit span
          • A researcher gave a number of digits and the participants is expected to recall them in the correct order
            • The number of digits is increased until they can no longer recall them in the correct order
          • The mean span for letters was 7.3
        • Joseph discovered that the mean digit span was 9.3
        • Evaluation points
          • Limitation: study was conducted a long time ago - lacks validity and control
          • Strength: Josephs results have been confirmed in other studies
      • George Miller (1956)
        • Created a span of memory and chunking
          • Discovered patterns of sevens (7)
            • He believed this suggested capacity of short term memory must be 7 (give or take 2)
          • chunking - people group sets of digits/units
    • Capacity
      • Alan Baddeley (1966)
        • Four groups of participants
        • Participants were given lists of words to remember
          • Acoustically similar words + Acoustically dissimilar      words + Semantically similar words + Semantically dissimilar words
            • Participants were asked to recall them in the correct order
              • When recalled immediately after learning hearing, they tended to do worse with acoustically similar words
              • After a time interval of 20 minutes, participants tended to do worse with semantically similar words
        • Evaluation points
          • Limitation: use of artificial stimuli - words have no personal meaning so are therefore not reflective of real life.
    • Duration
      • Margaret and Lloyd Peterson (1959)
        • conducted a study looking at short term memory
        • 24 participants took part in 8 trials
          • On each trial, they were given a consonant syllable as well as a three digit number
            • They were told to count backwards from the number until told to stop
              • Told to stop after different amounts of time
              • Prevented memory rehearsal of the syllable.
        • Evaluation
          • Limitation: use if artificial stimuli -doesn't reflect real life
          • Limitation: new information pushes out old in STM
      • Harry Bahrick (1975)
        • Conducted a study on LTM
          • Recall was tested in two ways:Photo recognition and free recall
            • participants who left school within 15 years were 90% accurate in photo recall, 70% after 48 years.
            • Free recall was worse than photo recognition
            • After 15 years after leaving, free recall was around 60% accurate, 30% after 48 years.
        • 392 participants from from Ohio aged between 17-74
          • High school Yearbooks were obtained
        • Evaluation
          • Strength - reflective of real life: meaningful memory
          • Limitation - couldn't control variables
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