Capacity

LTM - It is generally accepted amongest researchers that LTM has an unlimited capacity. It is possible to lose things from LTM through processes such as decay and interference but the loss does not occur because of capacity limitations.

STM - One of the earliest systematic attempts to measure the capacity of STM was carried out by Jacobs (1887) called the digit span technique which is where P's repeat back strings of digits in order of presentation. Jacobs found that on average people could recall about 7 digits in this immediate serial recall task and other research has supported this. George Miller wrote the famous article named 'The magical number seven, plus or minus two', in which he proposed that we can hold about seven items in our STM, but that there is a range of capacity between 5 and 9 items. Miller believed that our immediate memory span is determined by the number of 'chunks' of information we can hold rather than the number of individual letters or numerals. Many psychologists have criticized this idea of 'chunks' as it is too vague. Simon (1974) said that the span of the 'chunk' depends on the amount of information that is being processed.