peterson and peterson

• Peterson & Peterson (1959) investigated the duration of short-term memory by conducting a laboratory experiment with a sample of 24 psychology students.
• task: recall meaningless three-letter trigrams (for example, THG, XWV) at different intervals (3, 6, 9, 12, 15 or 18 seconds). 
• To prevent rehearsal (practice) the students had to count backwards in threes or fours from a specific number, until they were asked to recall the letters.
• Peterson & Peterson found that the longer the interval the less accurate the recall. At 3 seconds, around 80% of the trigrams were correctly recalled, whereas at 18 seconds only 10% were correctly recalled.
• Peterson & Peterson concluded that short-term memoryhas a limited duration of approximately 18 seconds.