psychology - memory

• Memory capacity


  • 712 items
  • Infinite capacity
• Memory duration


  • STM has a short duration
  • LTM lasts forever
• Memory coding


  • STM largely encoded acoustically
  • LTM largely encoded semantically
• What is the definition of capacity

  How much data can be held in a memory store
• Measuring memory capacity


  • Jacobs - digit span (9.3 for items, 7.3 for letters)
  • Miller - Memory span (7±2 ‘chunks’ of information)
• Memory capacity may be more limited than previously thought
• STM is likely to be limited to about 4 chunks
• Larger chunks (words/phrases) are remembered better than smaller chunks (syllables)
• Memory capacity decreases with age
• Memory duration


  How long a memory lasts before it is no longer available
• Measuring STM duration


  1. Participants given consonant syllable and 3-digit number

  2. Asked to recall consonant syllable after 2, 9, or 18 seconds

  3. 90% correct after 2 seconds, 20% after 9 seconds, 2% after 18 seconds
• Measuring LTM duration


  • Photo recognition test (50% accuracy after 15 years, 70% after 48 years)
  • Free recall test (67% after 15 years, 30% after 4 years)
• The studies on memory duration have low ecological validity as they do not reflect everyday memory activities
• Forgetting in the Peterson study may be due to displacement rather than decay