Capacity means the amount of space/information the STM can take. Meanwhile, duration means the amount of time the STM can store the information.
Capacity
The capacity for the STM is limited. One of the traditional ways of investigating the capacity of the STM is the serial digit span in which participants are asked to memorise a list of numbers/letters in order. There are many studies that investigate into this; most known, being Miller’s (1956) magic number 7+/-2. However, Jacobs’ (1887) study is a less difficult procedure in which a list of letters/numbers is viewed to them which they are expected to remember directly after the presentation. The difference between Jacobs’ and Miller’s procedure is that Jacobs’ gradually increased the length of the list up until the participant would only serial recall the list half of the time.
Jacobs had discovered that the capacity for the letters and numbers differ. Based on his average results, participants could remember 9 numbers and 7 letters. Another thing he discovered is that the older the participant was, the more he remembered. In conclusion, STM has the capacity of holding up to 9 pieces of information; and with age, you begin to gather different ways of remembering information more effectively.
Duration
The duration for the STM is also limited. Usually, the duration for the STM is measured by the Brown-Peterson technique. The name originated in 1959 as both Brown and Peterson + Peterson came up with this technique.
In the procedure, the participants are presented with trigrams in which 3 letters are viewed which don’t include vowels in avoidance of grouping/chunking. They are then asked to count backwards in 3s; this helps to prevent the possibility of rehearsal. A certain amount of time would pass by (i.e. 9 seconds) and then the participants are asked to write down or orally remember the trigram. Results are as