coding, capacity and duration of memory

• coding definition

  the format in which information is stored in various memory stores
• research on coding - Baddeley (1966)


  gave different lists of words to four groups of participants to remember: group 1 - acoustically similar, group 2 - acoustically dissimilar, group 3 - semantically similar and group 4 - semantically dissimilar

  when they did this task immediately recalling form the short term memory they tended to do worse with the acoustically similar words when recalling the words after a time interval of 20 min recalling from the long term memory they did worse on semantically similar words

  showing that information is coded acoustically in STM and semantically in LTM
• research on coding evaluation strengths

  identified a clear difference between two memory stores, STM uses mostly acoustic coding and LTM uses mostly semantic
• research on coding evaluation limitations

  it used quite artificial stimuli rather than meaningful material as the word lists had no personal meaning to the participants as if they had more meaning the STM may use semantic coding suggesting the study has limited application
• capacity definition

  the amount of information that can be held in a memory store
• research on capacity - Jacobs digit span (1887)

  the researcher reads out 4 digits and the participant recalls the digits then adds on another number and repeat until the participant cant recall them anymore

  Jacobs found that the mean span for digits across all participants was 9.3 and the mean span for letter was 7.3
• research on capacity - Miller 'magic 7'(1956)

  he made observations of everyday practices and noted that things come in sevens such as 7 days of the week, 7 deadly sins

  Miller thought that the span of STM is about 7 items plus or minus 2, he also noted that people can recall 5 words easily and do this by chunking
• research on capacity evaluation strengths

  Jacobs study has been replicated so the study is a valid test of digit span in the STM
• research on capacity evaluation limitation

  Miller may have overestimated the STM capacity as Cowan(2001) reviewed other research and said it was 4 plus or minus 1 chunks
• duration definition

  the length of time information can be held in a memory
• research on duration in STM - Peterson and Peterson (1959)

  tested 24 students, each student was given a consonant syllable to remember (such as YCG) and were told to count backwards until told to stop, the counting stops the mental rehearsal of the letters

  after 3 seconds, average recall was about 80% and after 18 seconds it was about 3% suggesting STM duration is about 18 seconds unless we are rehearsing it
• research on duration in LTM - Bahrick (1975)


  studied 392 American participants aged 17-74, high school recognition test

  participants tested within 15 years of graduation were about 90% accurate for photo recognition and after 48 years recall declined to 70%

  free recall of their names was less accurate as after 15 years was 60% and dropping to 30% after 48 years

  shows that LTM may last up to a lifetime for some material
• research on duration evaluation strengths

  Bahrick's study has high external validity as they investigated meaningful memories reflecting a more accurate representation of duration in memory
• research on duration evaluation limitations

  the stimulus material was artificial so the study lacked external validity as recalled consonant syllables does not reflect most everyday memory activities