Long-Term Memory

Long-term memory encompasses all learning or knowledge that is stored in the mind for longer than a few seconds or minutes. It encompasses all forms of learning and memory: memory for past events, facts, motor skills, perceptual skills, and conditioning.

Long-term memory interacts with short-term memory (also called working memory). Short-term memory consists of information currently being held in mind—the current contents of consciousness. The interactions between short-term memory and long-term memory are described in the Modal model of memory. In this model, perceptual information from the world is first stored in sensory system-specific buffers; in vision, this is referred to as iconic memory, and in audition, echoic memory. Some information can then pass from sensory memory into short-term memory; the amount of information is limited by attentional resources and the size of the short-term memory store. Once in short-term memory, information can be rehearsed; some information in short-term memory is transferred to long-term memory, generally information that receives more attention or is processed more deeply.

If information is not transferred to long-term memory, it cannot be retrieved later. A good illustration of the interactions among sensory, short-term, and long-term[Page 800] memory is in the common situation of looking up and calling a telephone number. When the telephone number is viewed in the phone book, it enters sensory memory, along with all the other information on the page. However, only the attended phone number moves from sensory to short-term memory. Once in short-term memory, the number can be rehearsed over a period of several seconds, allowing time to go to the phone and dial the number. However, if distracted, the number is lost from short-term memory and must be looked up again. The telephone number is only likely to enter long-term memory, and be accessible later, if the person pays attention to the number and processes its meaning and patterns. This deeper processing can include the use of mnemonic strategies.

There are several qualitative distinctions made within the area of long-term memory based on the type of material being maintained. The primary distinction is between declarative memory and nondeclarative memory. Declarative memory consists of knowledge that can be verbally stated (declared) and can be further subdivided into two forms, semantic and episodic. Semantic memory refers to memory for facts and definitions that are isolated from the specific point in time in which they were acquired. For example, the meaning of the word astronaut or knowledge that George Washington was the first president of the United States would be semantic memory.

Episodic memory refers to memory for the events of one's life, for example, remembering what happened at your 6th birthday party, or what you ate for breakfast this morning. Episodic memories tend to be complex memories in which specific persons and objects are related to each other and to time (what time of day, season, year) and place (what location). Episodic memory is typically assessed through tests of recall and recognition; in a recognition test, the person is presented with the memorized material and novel items and just has to indicate whether it was one of the memorized items or not; in recall, a person is given cues but must access the information from memory.

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