What we usually think of as “memory” in day-to-day usage is actually long-term memory, but there are also important short-term and sensory memory processes, which must be worked through before a long-term memory can be established. The different types of memory each have their own particular mode of operation, but they all cooperate in the process of memorization and can be seen as three necessary steps in forming a lasting memory.

This model of memory as a sequence of three stages, from short term to long-term memory, rather than as a unitary process, is known as the modal or multi-store or Atkinson-Shiffrin model, after Richard Atkinson and Richard Shiffrin who developed it in 1968, and it remains the most popular model for studying memory. It is often also described as the process of memory, but I have used this description for the processes of encoding, consolidation, storage and recall in the separate section.

It should be noted that an alternative model, known as the levels-of-processing model was proposed by Fergus Craik and Robert Lockhart in 1972, and posits that memory recall, and the extent to which something is memorized, is a function of the depth of mental processing, on a continuous scale from shallow (perceptual) to deep (semantic). Under this model, there is no real structure to memory and no distinction between short-term and long-term memory.