Bahrick (1975)

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

Method: Bahrick studied 392 former high school students: 162 males and 230 females, aged between 17 and 74. Each participant had belonged to a graduating class of at least 90 students for which a yearbook containing class photographs was available.

The participants were divided into nine groups based on the time since their graduation, ranging from 3 months to 47 years. They completed six tests:

• free recall

• matching names to photographs

• matching photographs to names

• photograph recognition, selecting the correct photograph from a group of five

• name recognition, selecting the correct name from a group of five

• photograph cueing, naming individual people shown in photographs

Results: Bahrick found that:

• performance was generally strongest on the name-recognition and name-matching tasks

• performance was weaker on the photograph-cueing and free-recall tasks

• after 14 years, participants were 90% accurate on the name-recognition and name-matching tasks

• after 47 years, participants were approximately 78% accurate on the name-recognition task

• after 47 years, participants were approximately 31% accurate on the free-recall task and less than 20% accurate on the photograph-cueing task

Conclusion: Bahrick concluded that information can remain in LTM for almost a lifetime - or at least 47 years. However, the amount remembered depends on how the information is tested, with recognition producing more accurate recall than free recall.