By Michael Howard, Ph.D.
How do memories get lost? The reasons can be found in any stage of the memory process: encoding, storage (consolidation), and/or retrieval. In the encoding stage, forgetting usually occurs because of inadequate attention to the material when it was acquired. In the storage or consolidation stage, several problems can develop. For instance, inadequate associations may not develop between new memories being formed and old memories already stored in the brain. There appears to be a natural time-linked decay of the information if it is not recalled occasionally.
Retrieval failure of memories can occur, especially when relevant cues are not present. Sometimes we can remember something and, other times we can’t. Certain situations may cue memories when others do not. For example, it may be easier to retrieve the memory of an event when you are in the same emotional state or same physical place you were in when the event occurred.
Forgetting is a normal process that aids in our ability to select out important information. Typically, we forget memories that are not meaningful to us. If you held onto memories for irrelevant facts, your brain would become quite cluttered and important information would be obscured. Forgetting unwanted or unneeded material obviously has evolutionary importance and helps in our adaptation and survival. For non-meaningful information, the greatest amount of forgetting occurs just after the information is put into long-term memory. This is called a “forgetting curve.” The forgetting curve is not nearly as steep for information that is important to us. We retain meaningful memories much longer.
Memory can also vary depending on how motivated we are to remember the event. We tend to forget things that we do not want to remember, such as traumatic events or very unpleasant information. This can be done in a conscious or unconscious manner. Some very traumatic events are thought to be unconsciously forgotten and are known as repressed memories. Methods for recovering these repressed memories in psychotherapy have created controversy concerning their validity.