1. Coding, Capacity and Duration of Memory

• 1. Coding, Capacity and Duration of Memory

  STM:

  • Coding = acoustically.
  • Capacity = limited (7+/-2).
  • Duration = 18 sec.

  LTM:

  • Coding = semantically.
  • Capacity = unlimited.
  • Duration = lifetime (47yrs).
• 2. Coding, Capacity and Duration of Memory

  Baddeley (1966) - Coding, STM + LTM:

  • Semantically similar, acoustically different words.
  • Acoustically similar, semantically different words.
  • STM = acoustic easy, semantic hard.
  • LTM = semantic easy, acoustic hard.
• 3. Coding, Capacity and Duration of Memory

  Jacobs (1887) - Capacity, STM:

  • Digit span test, numbers/letters.
  • 443 female students; repeat in same order (gradually increased).
  • 7.3 letters + 9.3 numbers.
• 3a. Coding, Capacity and Duration of Memory

  Miller (1956) - Capacity, STM:

  • ‘The Magical Number Seven, Plus or Minus Two’.
  • 7 items, plus/minus 2.
  • ‘Chunking’, e.g. phone numbers.
• 4. Coding, Capacity and Duration of Memory 


  Bahrick (1975) - Duration, LTM:

  • 392 American uni graduates.
  • Yearbook photos; match name/faces.
  • 90% = matched after 14yrs graduating.
  • 60% = matched after 47yrs graduating.
  • Duration = lifetime/47yrs; supports MSM.
• 4a. Coding, Capacity and Duration of Memory

  Peterson + Peterson (1959) - Duration, STM:

  • Lab exp; 24 psych students.
  • Recall 3-letter trigrams at different intervals (3,6,9,12,15,18 sec).
  • Prevented rehearsal by counting backwards 3/4s.
  • 3 sec = 80% recall.
  • 18 sec = 10% recall - limited duration.
• Coding, Capacity and Duration of Memory (Evaluation)

  Strength - Coding (STM/LTM):

  P - Baddeley (1966), clear diff between 2 memory stores.

  E - STM mostly acoustic; LTM mostly semantic.

  L - important step in understanding memory system, led to MSM.
• Coding, Capacity and Duration of Memory (Evaluation)

  Limitation - Coding (STM/LTM):

  P - Baddeley’s (1966) methodology criticised, doubt on validity of research.

  E - LTM tested by waiting 20min.

  L - questionable as to whether LTM actually tested.
• Coding, Capacity and Duration of Memory (Evaluation)

  Limitation - Coding (STM/LTM):

  P - some experiments show STM not exclusively acoustic, LTM not always semantic.

  E - Brandimote (1992), participants used visual coding STM if shown pictures + prevented verbal rehearsal.

  E - longterm recall related to visual as well as semantic (Frost, 1972); evidence of acoustic coding (Nelson + Rothbart, 1972).

  L - as verbal rehearsal prevented, participants used visual codes in STM, and LTM, evidence shows not always semantic.
• Coding, Capacity and Duration of Memory (Evaluation)

  Limitation - Coding (STM/LTM):

  P - Baddeley (1966), artificial stimuli.

  E - word lists no personal meaning; findings tell little about coding IRL.

  L - limited real-life application.
• Coding, Capacity and Duration of Memory (Evaluation)

  Limitation - Duration (LTM):

  P - Bahrick (1975), lacks population validity (392 American).

  E - unable generalise results to other populations.

  L - can’t conclude whether other populations show same ability of 47yrs duration.
• Coding, Capacity and Duration of Memory (Evaluation)

  Limitation - Duration (LTM):

  P - Bahrick (1975) results can’t explain whether LTM less accurate bc limited duration or bc gets worse w/ age.

  L - psychologists can’t determine whether LTM unlimited (like MSM claims) or limited.
• Coding, Capacity and Duration of Memory (Evaluation)

  Strength - Duration (LTM):

  P - Bahrick (1975), high ecological/external validity, real-life memories.

  E - recalled real-life info, match face/names.

  L - reflect memory for real-life events, applied to human memory.
• Coding, Capacity and Duration of Memory (Evaluation)

  Limitation - Duration (STM):

  P - Peterson + Peterson (1959) used 24 psych students.

  E - may’ve dealt w/ MSM, demand characteristics, lowers internal validity.

  E - student memory diff/better than others, studied memory strategies.

  L - can’t generalise results to non-psych students.
• Coding, Capacity and Duration of Memory (Evaluation)

  Limitation - Duration (STM):

  P - P + P (1959), low ecological validity.

  E - asked recall 3-letter trigrams, not something done IRL.

  L - unable conclude duration STM longer for more important info like phone numbers.
• Coding, Capacity and Duration of Memory (Evaluation)

  Strength - Duration (STM):

  P - P + P (1959), high control; lab study.

  L - controlled extraneous variables, study easy to replicate + high internal validity.
• Coding, Capacity and Duration of Memory (Evaluation)

  Strength - Capacity (STM):

  P - Jacobs’ (1887) study’s replicated.

  E - old study, lacked controls (cofounding variables).

  L - findings confirmed by better controlled studies, suggests valid test of digit span.
• Coding, Capacity and Duration of Memory (Evaluation)

  Limitation - Capacity (STM):

  P - Miller’s (1956), findings not replicated (low external reliability + temporal validity).

  E - overestimated capacity.

  E - Cowan (2001), meta-analysed studies of capacity, limited to 4 chunks.

  L - lower end of Miller’s range (7-2=5) more accurate.
• Coding, Capacity and Duration of Memory (Evaluation)


  Limitation - Capacity (STM):

  P - Miller (1956), didn’t specify how large each ‘chunk’ is.

  E - can’t conclude exact capacity.

  L - more research required to determine size of ’chunks’.
• Coding, Capacity and Duration of Memory (Evaluation)

  Limitation - Capacity (STM):

  P - Miller (1956) didn’t take into account other factors affecting capacity.

  E - e.g. age could affect STM.

  E - Jacobs (1887), STM improves w/ age; 6.6 digits (8y/o) and 8.6 (19y/o).

  L - may be due to increase in brain capacity as people age or development of recall strategies.