How we change what others think, feel, believe and do
The things that you are processing in your memory at any one time is the short-term memory. This is a limited store for things that you can think about at one time -- typically around seven.
Things get into short-term memory from two directions: directly from external senses or recalled from long-term memory. 'Thinking' as an act contains much switching of items to and from long-term memory.
In a computer metaphor, short-term memory is the cache on which the processor directly acts, as opposed to the longer-term store on the disk.
Items in short-term memory do not stay there by themselves and need constant attention and rehearsal to keep them in place. Without attention, they will typically remain for 20 to 30 seconds, but this can be much less (have you had someone introduced to you, then forget their name in seconds flat?).
Short-term memory was described by James (1890) as primary memory (long-term memory being called secondary memory).
The classic paper on short-term memory is Miller (1956), who noted that it contained 'seven, plus or minus two' slots, into each of which one chunk of information can be placed. Further research (Cavanagh, 1972) has shown that the number of slots depends on the task at hand and can be as little as three.
The size of any one chunk can vary depending on the associations that it has and hence how it can be thought of as a single concept. Thus, for example, RFB may be stored as three separate chunks, whilst GOD is held as a single chunk.
It is notable that newspaper columns often hold on average about seven words. This allows the whole line to be taken in at one glance without having to move the eyes horizontally. Thus you can read quickly and easily by scanning downwards only.
Do not try to handle too much information at once, particularly when you are learning a new subject.
Remember that when you are talking to someone less expert than you about a subject, you may be able to hold complex items as a single chunks, whilst they will have to break them down -- this makes it much harder for them to process and understand what you are saying. To get others to think about more things at once, first build solid concepts that can be processed as a single chunk.
Cavanagh, J.P. (1972). Relation between the immediate memory span and the memory search rate. Psychological Review, 79, 525-530
James, W. (1890). Principles of Psychology, New York: Holt
Miller, G.A. (1956). The magic number seven (plus or minus two): Some limits on our capacity for processing information, Psychological Review, 63, 81-93