Episodic memory refers to memories of specific episodes in one’s life and is what most people think of as memory. Episodic memories are connected with a specific time and place. If you were asked to recount everything you did yesterday, you would rely on episodic memory to recall the events. Similarly, you would draw on episodic memory to describe a family vacation, the way you felt when you won an award, or the circumstances of a childhood accident. Episodic memory contains the personal, autobiographical details of our lives.
Semantic memory refers to our general knowledge of the world and all of the facts we know. Semantic memory allows a person to know that the chemical symbol for salt is NaCl, that dogs have four legs, that Thomas Jefferson was president of the United States, that 3 × 3 equals 9, and thousands of other facts. Semantic memories are not tied to the particular time and place of learning. For example, in order to remember that Thomas Jefferson was president, people do not have to recall the time and place that they first learned this fact. The knowledge transcends the original context in which it was learned. In this respect, semantic memory differs from episodic memory, which is closely related to time and place. Semantic memory also seems to have a different neural basis than episodic memory. Brain-damaged patients who have great difficulties remembering their own recent personal experiences often can access their permanent knowledge quite readily. Thus, episodic memory and semantic memory seem to represent independent capacities.