What memory is

Why can you still sing a song you heard years ago, yet forget a formula you learnt last term? This chapter explains how memories are made, kept and lost.

Memory is the process of retaining and recalling information over a period of time. Many people think memory means only 'remembering'. In fact the work of memory begins the moment you experience something, long before you try to recall it.

The first systematic study of memory was done by Hermann Ebbinghaus in 1885. He learnt lists of nonsense syllables (such as NOK, SEB) himself and tested how much he remembered after different gaps, so that meaning and past knowledge could not help him.

Memory works in three stages:

• Encoding: the first stage, when information is recorded and registered so that the memory system can use it. Information from the senses is turned into a form the brain can handle, and is given meaning.
• Storage: retaining the encoded information over time so that it can be used later.
• Retrieval: bringing stored information back to awareness when it is needed, for example to answer a question or solve a problem.

Memory can fail at any of the three stages. If you were half-listening while a friend told you a phone number, it may never have been encoded. If it was encoded but then lost, storage failed. If you know you know it but it will not come, retrieval failed.

Memory is not a passive storehouse that keeps exact copies. It is an active, constructive process. Frederick Bartlett showed that when people retell a story, they change it to fit what they already know and expect (their schemas), leaving out unfamiliar details and adding familiar ones.