Semantic memory refers to a portion of long-term memory that processes ideas and concepts that are not drawn from personal experience. Semantic memory includes things that are common knowledge, such as the names of colors, the sounds of letters, the capitals of countries and other basic facts acquired over a lifetime.

The concept of semantic memory is fairly new. It was introduced in 1972 as the result of collaboration between Endel Tulving of the University of Toronto and Wayne Donaldson of the University of New Brunswick on the impact of organization in human memory.

Tulving outlined the separate systems of conceptualization of episodic and semantic memory in his book, "Elements of Episodic Memory." He noted that semantic and episodic differ in how they operate and the types of information they process.

Before Tulving, human memory had not undergone many in-depth studies or research. Since then, a number of research projects have investigated the differences between semantic and episodic memory. Some of the most notable experiments relating to semantic memory were conducted by J.F. Kihlstrom in the 1980s to test hypnosis on semantic and episodic memory.

Semantic vs. episodic memory

Semantic memory is the recollection of facts gathered from the time we are young. They are indisputable nuggets of information not associated with emotion or personal experience.

Some examples of semantic memory:

Knowing that grass is greenRecalling that Washington, D.C., is the U.S. capital and Washington is a stateKnowing how to use scissorsUnderstanding how to put words together to form a sentenceRecognizing the names of colorsRemembering what a dog isKnowing how to use the phoneKnowing that President John F. Kennedy was shot on Nov. 22, 1963Episodic memory is specific to the individual. It is the recollection of biographical experiences and specific events in time in a serial form, from which we can reconstruct the actual events that took place at specific points in time in our lives.

Examples of episodic memory:

Recalling where you were when Kennedy was shotReminiscing about your first kissRecalling your first day of schoolKnowing the name and breed of your first dogRemembering your wedding dayRecalling the guests at your best friend’s 30th birthday partyKnowing your lab partner in college chemistry classRemembering your first day on a new job

Moving from episodic to semantic memory

There is a steady movement of memories from episodic to semantic, especially during childhood when we are continuously learning new things. For example, learning how to use the phone may start out as an episodic memory of dialing a phone number on a toy telephone. That knowledge then becomes cemented in long-term memory.

Semantic memory is generally derived from episodic memory, in that we learn new facts or concepts from our experiences, and episodic memory is considered to reinforce semantic memory. Researchers generally agree that there is typically a gradual transition from episodic to semantic memory, in which episodic memory reduces its sensitivity and association to particular events, so that the information can be stored as general knowledge. For instance, you know how to use a phone, but don’t remember the early knowledge you acquired playing with a toy phone. [Mystery of Memory: Why It's Not Perfect]

But that does not mean that all semantic memories begin as episodic memories, Tulving argued. “If a person possesses some semantic memory information, he obviously must have learned it, either directly or indirectly, at an earlier time, but he need not possess any mnemonic information about the episode of such learning,” he wrote.