memory variable studies

• Who studied duration?

  • Peterson and Peterson - trigrams + counting backwards
  • Bahrick et al - yearbook
• Outline Bahrick et al's study- Yearbook


  • Tested the LTM of 392 participants.
  • Tested 15 years, 30 years, and 48 years after graduation.
  • Tested free recall, photo recognition and name recognition
• What were the findings of Bahrick et al's study?

  • 30 years after graduation:
  • There was only 30% accuracy for free recall.
  • 48 years after graduation:
  • Name-recognition was 80% accurate.
  • Photo-recognition was 40% accurate.
  • Overall, through the years recognition was more accurate than recall.
• Outline Peterson and Peterson's study - counting backwards


  • Laboratory experiment.
  • 24 psychology students
  • Recall random trigrams after intervals (3, 6, 9, 12, 15, and 18 seconds).
  • Had to count backward - stopped maintenance rehearsal
• What were the findings of Peterson and Peterson?

  Participants could recall fewer trigrams as the time gap increased.

  • 3-second interval - 80% correctly.
  • 6-second interval - 50% correctly.
  • 18-second interval - 10% correctly.
• Outline sperling - grid recall

  • Showed the participants a grid of letters (three rows of four letters) for 0.05 seconds (50 milliseconds).
  • There were two different scenarios:
  • Recall the whole grid.
  • Recall a single row.
• What were the findings of the Sperling - grid recall?


  • First scenario - recall the whole grid:
  • four or five letters out of a total of 12 letters.
  • Second scenario - recall a single row:
  • 3 out of 4 letters recalled
  • Suggests the STM is finite
• Who studied capacity?

  Sperling - grid recall

  Jacobs - sequencing
• What shape is Murdock's 'serial position curve'

  U shaped
• What is the Murdock - serial position curve?


  • the probability of recalling any word depended on its position in the list
  • early in the list (the primacy effect)
  • end of the list (the recency effect)
  • were more often recalled, but the ones in the middle were more often forgotten.