Sigmund Freud theorized that people intentionally forgot things in order to push bad thoughts and feelings deep into their unconscious, a process he called "repression".There is debate as to whether (or how often) memory repression really occurs and mainstream psychology holds that true memory repression occurs only very rarely.

One process model for memory was proposed by Richard Atkinson and Richard Shiffrin in the 1960s as a way to explain the operation of memory. This modal model of memory,