Coding, Capacity and Duration

• Baddeley's research into coding


  1. Participants given 1 of 4 word lists to remember:

  2. Acoustically similar

  3. Acoustically dissimilar

  4. Semantically similar

  5. Semantically dissimilar

  6. Participants asked to recall words in correct order either immediately (STM) or after 20 mins (LTM)
• Baddeley's findings on coding

  • In STM, participants did worse on acoustically similar words
  • In LTM, participants did worse on semantically similar words
• Jacobs' research into capacity


  Participants shown series of numbers or letters that increased by one digit each time, then asked to recall from memory
• Jacobs' findings on capacity

  • Average span was 7.3
• Miller's "magic number"


  7 +/- 2
• Cowan's findings on capacity


  • Capacity of STM is only 4 +/- 1
• Peterson and Peterson's research into STM duration

  24 students shown trigrams and had to recall after counting backwards in 3s, with varying time delays
• Peterson and Peterson's findings on STM duration

  • When rehearsal is prevented, STM lasts about 18 seconds
• Bahrick et al's research into LTM duration


  392 participants tested on memory of classmates with either free recall or photo recognition
• Bahrick et al's findings on LTM duration


  • Photo recognition was higher than free recall after 15 and 48 years, LTM duration is essentially limitless
• Coding - Conclusion

  information is coded acoustically in STM and semantically in LTM
• Coding limitation

  use of artificial stimuli doesn’t tell us anything about coding in everyday life
• Eval Duration:

  • STM research had meaningless stimuli of trigrams so cannot be generalised to real life
  • LTM used meaningful memories so has high external validity