Semantic memory is considered an independent system in models of memory (Tulving 1972). It processes, stores, and retrieves information about the meaning of things, without any reference to a specific temporal and spatial context.
Definition and Overview
Semantic memory is the primary type of memory involved in recognition and refers to the memory of meaning, understanding, general knowledge about the world and other concept-based knowledge unrelated to specific experiences.
The experience of semantic memory involves accessing knowledge about the world that does not have to be tied to any specific personal experience. This knowledge can be things like facts, vocabulary, numbers, and concepts. Semantic memory is what we refer to when we speak of knowing as opposed to remembering, which pertains to episodic memory Opens in new window.
Knowing that all birds have two legs is an example of a semantic memory. Remembering that a particular bird landed in a tree outside my window at around 11:00 A.M. last Sunday morning, on the other hand is an example of an episodic memory.
Unlike episodic memory Opens in new window, when we experience semantic memory, we are not traveling back to a specific experience in our past, but we are experiencing things we are familiar with and know about.
For example, I know many facts about the Pacific Ocean Opens in new window—where it is located, that it is big, that if you travel west from San Francisco you end up in Japan.
All of these things are semantic memories. Tulving Opens in new window describes the experience of semantic memory as knowing, with the idea that knowing does not involve mental time travel.
Much of semantic memory is related to the abstract categories of language Opens in new window. Activities such as denominating a picture, defining a word, sorting pictures into categories, or pointing out pictures among a set of distracters require intact access to representations in semantic memory.
Although semantic memory is a component of the declarative system Opens in new window of long-term memory Opens in new window, some semantic memories are often used nondeclaratively, without our even being conscious of them.
Much of our abstract categorical knowledge about the world is employed in the selection of sensory input, a recognition process that usually takes place outside conscious awareness. This process is based on identifying the things around us by processing them through the appropriate semantic categories.
Semantic memory can thus be either declarative (explicit) Opens in new window or nondeclarative (implicit) Opens in new window. With continued, regular use, concepts Opens in new window in semantic memory are evoked automatically, and hence become nondeclarative (implicit).
Trying to recollect what the capital of Idaho is would be an explicit (declarative) use of semantic memory whereas immediately recognizing and naming an apple would be an implicit (nondeclarative) use.
Connections Between Semantic and Episodic Memories
Most of our experiences involve both episodic and semantic memory, and the two interact in many ways.
Our (semantic) categories are built up from particular (episodic) experiences, and our particular (episodic) experiences are of things that usually fit into our (semantic) categories.
The relation between particular experiences and generalized categories is of course different for each person.
The illustration or prototype of a category is to some extent personal because the particular episodic memories which are related to each semantic category are different for each person.
In addition, the formation of semantic memories is not a static process; we continue to elaborate and refine our semantic memory categories, and to create new categories all our lives.
Although eventually the details of episodic memories of similar experiences are lost, an abstract schema derived from commonalties running through all the experiences remains.
This schema Opens in new window is a more general type of semantic memory category. Whereas knowledge categories deal with particular types of objects or single events, schemas are like metacategories: they are categorizations of entire type of situations.
It appears that most of our episodic memories undergo this evolution into semantic memories over time. That is, most of our particular experiences eventually merge into general categories and lose their specific details.
Unlike the formation of episodic memories Opens in new window, which seems to be a rapid capturing process, the formation of semantic memories is a result of a slow accumulation.