Coding, capacity and duration of memory

• Coding, capacity and duration of memory-

  Coding-

  • Baddeley (1966) investigated the coding of memory through groups that he gave different types of words, they were asked to recall them in the correct order.
  • The task was done immediately, so it was recalled from the participants short term memory, and also after 20 minutes, so the words were in the long-term memory.
• Coding, capacity and duration of memory-

  coding-

  • Group 1: acoustically similar (cat, cab, can)
  • Group 2: acoustically dissimilar (pit, few, cow)
  • Group 3: semantically similar (large, big, huge)
  • Group 4: semantically dissimilar (hot, grass, good)
  • Findings suggest that information is coded acoustically for STM and semantically for LTM.
• Coding, capacity and duration of memory-

  coding-

  S- A clear difference is identified between the short and long term memory.

  W- Artificial stimuli for the test, instead of a meaningful material, so the results have limited application. 
• Coding, capacity and duration of memory-

  capacity-

  • Jacobs (1887) investigated digit span, where a reader reads out 4 digits and the participant recalls them aloud in order, if correct the reader reads out 5 digits etc.
  • Mean digit span was 9.3 items, and 7.3 for the letter span.
  • Miller (1956) made observations that the magic number was 7 (7 days of the week, 7 deadly sins, 7 musical notes on the scale).
  • Believed that the STM capacity was 7 +/- 2.
  • People are able to recall 5 digits as well as they can recall 5 words, this is done via chunking.
• Coding, capacity and duration of memory-

  capacity-

  S- Study has been replicated, ensuring the results are correct, due to some participants being possibly distracted (confounding variable).

  W- Overestimated STM capacity, Cowan (2001) reviewed other research and concluded the capacity of STM was 4 +/-1.
• Coding, capacity and duration of memory-

  duration-Short Term Memory (STM)-

  • Peterson and Peterson (1959) tested 24 students in 8 trials each, giving each a 3 digit and letter sequence (475 and YGC).
  • They had to count backwards from the number until instructed to stop to stop internal rehearsal of the sequences.
  • They had to stop after 3,6,9,12,18 second intervals; after 3 seconds the average recall was 80%, and after 18 it was around 3%.
  • Peterson and Peterson’s findings suggest that STM can last for 18 seconds, and longer with rehearsal.
• Coding, capacity and duration of memory-

  Duration- Long Term Memory (LTM)-

  • Bahrick et al (1975) had 392 aged 17-74 Americans and used their school yearbook to test LTM.
  • They used photo recognition using 50 photos (some real), free recall where the participants just recalled he names of those in their graduation class.
  • Those within 15 yrs of graduation were 90% accurate with the photos, after 48yrs it became 70%.
  • Free recall was about 60% after 15 yrs and went to 30% after 48yrs.
  • LTM can last a lifetime.
• Coding, capacity and duration of memory-

  duration-

  S- Bahrick has high external validity due to the stimulus being meaningful through the participants memories like the people's names and faces – when LTM is assessed with a meaningless stimulus the results are lower (shepherd 1967).

  W- Peterson and Petersons study used an artificial stimulus, so it lacked external validity, but still has some validity due to people having to remember number/letter sequences (passwords).