Duration of Long Term Memory - Bahrick (1975)

• Bahrick (1975) studied the duration of the LTM.
• Aim of Bahrick (1975)

  To establish the duration of the LTM including recognition and recall - in a lab experiment.
• Procedure

  • Investigators tested the memory of 392 graduates of an American High School for their former classmates from a 50 year period.
  • There were two conditions:

  1. half the participants were given a group of names and asked to select the name that matched the person in the photo (recognition group).
  2. The other half were simply asked to name the people in the photos without being given a list of possible names (free recall group)
• Findings

  • In the recognition group participants were 90% correct after 14 years.
  • 80% correct after 25 years.
  • 75% correct after 34 years.
  • 60% correct after 47 years.
  • In the recall group 60% at 7 years but dropped to less than 20% after 47 years.
• Conclusions:

  • People can remember certain types of information for almost a lifetime
  • The accuracy of the LTM is better when measured by recognition than recall tasks
• Evaluation of Bahrick (1975)

  ☺ A strength is that the study had high external validity. Bahrick used meaningful material (high school yearbooks) and tested people for memories from their own lives. When lab studies are carried out with meaningless pictures to be remembered, the recall rates were lower.
• Evaluation of Bahrick (1975)

  ☹ The downside of real-life research like this is that cofounding variables could not be controlled, such as the fact that Bahrick's Ps may have looked at their yearbooks and rehearsed the memories over the years.
• Evaluation of Bahrick (1975)

  ☹ It is unclear whether the drop-off in accuracy after 47 years is due to passage of time or ageing effects in the brain of older participants.