Coding, capacity and duration of memory

• Research on coding

  • Short-term memory (STM): Information encoded acoustically (sound-based).
  • Long-term memory (LTM): Information encoded semantically (meaning-based).
  • Study: Baddeley (1966) tested different word lists for STM and LTM recall.
  • Finding: Acoustically similar words were harder to recall in STM. Semantically similar words were harder in LTM
• Evaluation of coding research

  Limitation: Artificial stimuli (word lists) might not reflect everyday memory use. Generalisation Caution: Findings may differ when processing meaningful information. Conclusion: Semantic encoding applies to LTM, and possibly to more meaningful tasks.
• Research on Capacity (Digit Span)

  • Study: Jacobs (1887) developed a technique to measure digit span.
  • Method: Participants recalled sequences of digits.
  • Finding: Average digit span was 9.3; average span for letters was 7.3.
• Span of Memory and Chunking

  • Study: George Miller noted that people can recall around 7 items (plus or minus 2).
  • Chunking: Grouping digits/letters into chunks helps recall more information (e.g., 5 words = 5 chunks).
• Evaluation of Capacity Research

  • Limitation: Study may lack validity due to distractions during testing.
  • Findings: Confirmed by other research.
  • Limitation: Cowan (2001) suggests STM capacity is closer to 4 chunks rather than 7.
• Research on Duration of STM

  • Study: Peterson and Peterson (1959) tested STM duration using consonant syllables.
  • Finding: STM duration is very short (around 18 seconds) unless rehearsed.
• Research on Duration of LTM

  • Study: Bahrick et al. (1975) tested LTM using participants' recall of classmates' names after years.
  • Finding: After 48 years, participants still had about 70% accuracy in recognition of names.
• Evaluation of STM Duration Study

  • Limitation: Study used artificial stimuli (nonsense syllables) which may not reflect real-world memory.
  • Strength: Lacked external validity but was useful for specific tasks like phone number recall.
• Evaluation of LTM Duration Study

  • Strength: High external validity due to real-life material used (e.g., classmates' photos).
  • Limitation: Confounding variables (e.g., participants looking at yearbooks) might have affected the results.
• Critique of Peterson and Peterson

  • Issue: The rapid decay of STM memory may result from displacement (new information pushes out old information).
  • Validity: This suggests Peterson and Peterson's study may have lacked internal validity.