Peterson & Peterson (1959)

Peterson and Peterson (1959) Aim

To investigate the duration of short-term memory, and provide empirical evidence for the multi-store model.

Peterson and Peterson (1959) STM Method

A lab experiment was conducted in which 24 participants (psychology students) had to recall trigrams (meaningless three-consonant syllables, e.g. TGH). To prevent rehearsal participants were asked to count backwards in threes or fours from a specified random number until they saw a red light appear.

Participants were asked to recall trigrams after intervals of 3, 6, 9, 12, 15 or 18 seconds. During the pause, they were asked to count backwards in 3's from a given number. This interference task was prevent rehearsal.

Peterson and Peterson (1959) Results

The longer the interval delay the less trigrams were recalled. Participants were able to recall 80% of trigrams after a 3 seconds delay. However, after 18 seconds less than 10% of trigrams were recalled correctly.

Peterson and Peterson (1959) Conclusion

Short-term memory has a limited duration when rehearsal is prevented. It is thought that this information is lost from short-term memory from trace decay. The results of the study also show the short-term memory is different from long-term memory in terms of duration. Thus supporting the multi-store model of memory.

Evaluation - Strength

Well controlled lab study. e.g. instructions to pps were standardized. improves internal validity of study as extraneous variables were controlled.

Evaluation - Weakness 1

This experiment has low ecological validity as people do not try to recall trigrams in real life.
(Lab setting is artificial so lacks ecological validity, therefore results can't be generalised to real-life.)
Learning nonsense trigrams is not a day-to-day activity, so task lacks mundane realism.

Evaluation - Weakness 2

Use of students is problematic. results may not relate to general population and so lack population validity. Uni students are above average intelligence, so memory task with another group may show different results.