Memory can be defined as the ability to encode information and retrieve it when necessary. Its basic processes are the acquisition of information (encoding), the ability for that information to persist over time (storage) and the accessing of that information (retrieval) (Bunnel, 1999).

Models of memory are used to help us understand how the memory works. The basic structure of memory consists of sensory, short-term and long-term memory. Many of the models developed argue that there is more to memory than these three basic structures but most research and writings start somewhere with these three. Models of memory vary in the way they believe information is encoded, stored and retrieved.

The memory system is located in the brain and the brain stem, at the top of the spinal cord. It is well known that different portions of the brain perform different memory functions, and it turns out that a part of the brain stem is involved in registering information into long-term memory. The temporal lobes are also involved in registering memory. Additionally, different types of memories are located in specific parts of the brain. Because the memory system is made of brain tissue, your memory performance is of course directly affected by the state of your brain. Poor health, fatigue, malnourishment, and substance abuse can all lead to lousy memory performance (Herrmann, Raybeck and Gutman, 1993).

When memory fails us, it does so in one of three ways. It can fail to register something initially in memory; it can fail to retain over time that which was successfully registered; or it can fail to remember something, despite successful registration and retention (Herrmann, Raybeck and Gutman, 1993). The former is often referred to as "pseudo-forgetting" because the information was never really known in the first place. Another form of pseudo-forgetting is called mental blur forgetting; it comes from incomplete learning such that a clear neural trace is never fully stored in the brain.

The single most important aspect of the memory system for improving memory performance is the process of attention. The likelihood that information in working memory will be absorbed or lead certain traces to emerge from long-term memory depends on how intensely we pay attention to the information in working memory. A good memory requires an ability to set a high level of attention for all memory tasks and to control the distribution of attention.

Four approaches to the study of Memory: