Short term and Long term memory

Duration of STM


Capacity of STM

Encoding in STM and LTM

HideShow resource information

Peterson and Peterson (1959) - duration of STM

Method: Ppts shown nonsense trigrams (CVM). Asked to recall after either 3, 6, 9, 12, 15, 18 secs. During pause, asked to count backwards in 3s from given number (interference task)

Results: After 3 secs : 80% correct recall

              After 18 secs 10% correct recall

Conclusion: When rehearsal prevented, little stays in STM longer than 18 secs

Evaluation: Reliable. Lab experiment, variables controlled.

                   Nonsense trigrams artificial. Lacks ecological validity.

                   Meaningful / real life memories may last longer. Duration depends on stimulus

1 of 3

Bahrick et al (1975) - very long term memories

Method: 329 people asked to list names of ex-classmates. Then either shown photos and asked to recall names of people or given names and asked to match to photo.

Results: 15 years of leaving school, recognise 90% of people. 60% on free recall.

               30 years free recall 30%

               48 years name recognition 80%, photo 40%

Conclusion: VLTM's in real life. Recognition better than recall, may be huge store of info but no easy access.

Evaluation: Field, high eco. validity

                             hard to control variables, less reliable

2 of 3

Jacobs (1887) - Capacity of STM

Method: Ppts presented with string of letter / digits

              Asked to repeat back in same order

              Amount of digits / letters increased till ppt failed

Results: Ppts recalled 9 digits / 7 letters

              Capacity increased with age during childhood

Conclusion: STM has limited capacity (5-9 items)

Increased with age due to increased brain capacity? or use of memory techniques 

Digits easier as only 10 different whereas 26 letters

Evaluation: Artificial. Lacks ecological validity

                   Meaningful Information recalled better. Maybe STM has greater                                capacity?

3 of 3


No comments have yet been made

Similar Psychology resources:

See all Psychology resources »See all Memory resources »