[Added July 1996]
Immediate memory allows the mind to hold and let go of a sensory impression within a very short time. If you look at an image and close your eyes, you’ll remember it for only about a second unless you ‘decide’ to store it.This temporary sensory is necessary to allow the brain to process for example the speech heard.
Short-term memory lasts about a minute. We use it, for instance, to retain
a phone number between reading it in the phone book and dialling.
Short-term memory can hold about seven items.
Long-term memory can last many decades.
It is estimated that the human brain could hold more then 1,000 times the
information contained in a large 20-volume encyclopaedia.
Then we have episodic memory , semantic memory and procedural memory.
You remember a ride with a horse, the meaning of the word “horse”, how to
ride a horse.
This classification can be useful to develop memorisation strategies.For example
it is easy to remember something you have done only once(episodic memory);
so why not memorising some difficult semantic information (for example meaning
of foreign words) by learning them when you visit a place never seen before, or
do in general something new.
Concerning long term memory, a more detailed discussion distinguishes between declarative memory (that includes what we called semantic and episodic memory) as things that we recall by speaking and non declarative memory or things that we recall by doing. Declarative memory is based on hippocampus and is also called explicit. Non declarative memory is based on parts of the brain different from hippocampus. Non declarative memory includes implicit i.e. memory at work when we remember how to do things. It includes also procedural memory : this is at work in priming, conditioning, etc…