Duration of the STM

• Margret and Lloyd Peterson (1959) tested 24 students in eight trails each
• on each trial the student was given a consonant syllable to remember
• they were also given a three digit number
• the student counted backwards from this number until they were told to stop
• The counting backwards was to prevent any mental rehearsal of The consonant syllable (which would increase the duration of STM Memory for the syllable)
• On each trial they were told to stop after varying periods of time: 3, 6, 12, 15 or 18 seconds (the retention interval)
• Recall was generally accurate after 3 seconds (over 80%) but by 18 seconds it Declined to around 10%
• It was concluded that the duration of STM is around 18-30 seconds, if rehearsal is prevented (we don’t practice)