duration

• Duration of the STM was tested by Marget and Lloyd Peterson in 1959. They did this by giving 24 students a constant syllable and asking them to recall it after certain time periods and it was usually done in seconds. They also did a similar technique with a three digit number and they were asked to count backwards until they reached that number they were given. After a longer period of time the amount of participants that remembered decreased.
• Duration of the LTM was tested by Harry Bahrick in 1975. He did this by getting people who had graduated from ages 17-74 and retained their high school yearbooks. He first got them to do a photo recognition and then secondly a free recall test where they recalled the names. 

  As the age increased the percentage of the participants that remembered decreased.
• One limitation of Peterson's research is that the stimuli was artificial. This means that the study was not totally meaningless as we sometimes have to remember less meaningful information.  As recalling constant syllables is not needed in everyday life. This means that this study lacks external validity.
• One strength of Bahrick's research is that it has high external validity. This is because he investigated meaningful memories. When studies on LTM covered meaningless pictures to be remembered, the recall rates were lower. This suggests that his findings reflect a more real estimate of the duration of the LTM.