Duration of LTM - Bahrick (1975)

Question 1

Aim

Answer 1

To investigate the duration of long-term memory (LTM).

Question 2

Procedure

Answer 2

• Natural experiment.
• Sample of 392 American university graduates ranging from 17-74 years.
• Participants were asked to either bring in their yearbooks or their yearbooks were taken directly from their school.
• Participants were then placed into 2 conditions:

1) Free recall - name every student you went to school with.
2) Photo recognition - name the students in 50 pictures.

Question 3

Findings

Answer 3

Free recall
1) If graduated within 15 years - 60% accuracy
2) If graduated within 48 years - 30% accuracy

Photo recognition
1) If graduated within 15 years - 90% accurate recall
2) If graduated within 48 years - 70% accurate recall

Question 4

Conclusion

Answer 4

Memories remain in the LTM for at least 48 years, perhaps a lifetime.

Question 5

Strength

Answer 5

• The study used real-life memories (school yearbooks), making the findings more generalisable to everyday memory use.
• High levels of ecological validity.

Question 6

Weakness

Answer 6

• Cannot establish causality.
• Since it was a natural experiment, we cannot determine whether LTM becomes less accurate overtime due to age or a limited duration.
• This is important because psychologists are unable to determine whether our LTM has an unlimited duration (like the multi-store model suggests), which is affected by other factors, such as getting older, or whether our LTM has a limited duration.

Question 7

Weakness

Answer 7

• Good sample size of 392 American university students and broad age range.
• However, findings are Western-based, limiting its application to other aspects of the population, e.g., Europeans.

Question 8

Weakness

Answer 8

• Lack of control over extraneous variables.
• Some participants may have looked at their yearbooks before the study of kept in touch with classmates, which could have boosted memory artificially.
• Lacks internal validity.