Coding, capacity & duration

• Research on coding:

  Baddeley gave different lists of words to 4 groups of ppts to remember

  1. acoustically similar (cat, cab, can)
  2. acoustically dissimilar (pit, few, cow)
  3. semantically similar (great, large, big)
  4. semantically dissimilar (good, huge, hot)

  when they did the task immedialtely from STM they did worse with acoustically similar words. When they recalled after 20 minutes from LTM they did better on semantically similar words. This suggests info is coded semantically in LTM & acoustically in STM
• Research on capacity:

  Digit span-

  Jacobs measured digit span to find out how much info the STM can hold at once. Researcher read out 4 digits and ppt recalls out loud in the correct order. If ppts get it correct then the researcher calls out 5 digits and so on until the ppts can't recall the order correctly. This indicates an individual's digit span.

  Jacob found the mean span for digits was 9.3 items. The mean span for letters was 7.3
• Research on capacity:

  span of memory and chunking-

  Miller noted that things come in 7's: 7 notes on the musical scale, 7 days a week, 7 deadly sins etc. Miller thought the span of STM was 7 items plus or minus 2. He also noted we can recall 5 letters as easily as we can recall 5 words. we do this by chunking- grouping sets of digits or letters into units or chunks.
• Research on duration of STM:

  Peterson & Peterson did a lab experiment with 24 psych students. They had to recall nonsense 3-letter trigrams (E.G, XWV) at different intervals. To stop rehearsal the students counted backwards in 3's or 4's from a specific number, until they were asked to recall the letters. they found longer intervals = less accurate recall. At 3 secs, 80% of the trigrams were correctly recalled, at 18 seconds 10% were correctly recalled. Peterson & Peterson concluded that STM has a limited duration of 18 secs. if we don't rehearse information, it will not be passed to LTM
• Research on the duration of LTM:

  Bahrick (1975)used 392 American university graduates. They were shown photographs from their high-school yearbook and were given a group of names and asked to match the names to the photographs. he found that 90% of the participants correctly matched the names and faces 14 years after graduating. 60% were able to correctly match 47 years after graduation. He concluded that people could remember certain types of information for almost a lifetime.
• EVALUATION OF RESEARCH ON CODING:

  1. one strength is Baddeley's study identified a clear difference between the 2 memory stores. Later research showed there are some exceptions to his findings but the idea that STM uses acoustic coding and LTM uses semantic remains the same.
  2. The limitation is that the study used artificial stimuli. the word list had no personal meaning to ppts.
• EVALUATION OF RESEARCH ON CAPACITY (Jacobs):

  1. one strength is that it has been replicated. the original study is very old and often old studies lack adequate control but Jacobs' findings have been confirmed by other, better-controlled studies since then. This suggests it is a valid study
• EVALUATION OF RESEARCH ON CAPACITY (Miller):

  1. One limitation is he may have overestimated the STM capacity. Cowan reviewed other research and concluded that the capacity of the STM is only about 4 plus minus 1 chunks.
• EVALUATION ON RESEARCH OF DURATION (Peterson):

  1. One limitation is the stimulus material was artificial. the study is not completely irrelevant because we do sometimes try and remember useless material but it doesn't reflect everyday activities where what we try to remember is meaningful. The study lacks external validity
• EVALUATION OF RESEARCH ON DURATION (Bahrick):

  1. one strength is that Bahrick's study has high external validity. This is because the researcher investigated meaningful memories.