LONG-TERM MEMORY (LTM) efficiently stores our knowledge about the world. It is important to contrast LTM with other types of memory and understand how it is structured. The knowledge we store in LTM affects our perceptions of the world, and influences what information in the environment we attend to. LTM provides the framework to which we attach new knowledge, and its properties have important implications for instructional design.

Long-term memory (LTM) contrasts with short-term and perceptual memory in that information can be stored for extended periods of time. LTM allows retrieval of information decades after it is stored, and the limits of its capacity are not known.

LTM is stored in networks of schemas.

Schemas are mental models of the world. Psychologists believe that information in LTM is stored in large, interrelated networks of these schemas, which form intricate knowledge structures. Related schemas are linked together, and information that activates one schema also activates ones that are closely linked. This allows relevant knowledge to be called up when information is presented.

LTM has a strong influence on perception through top-down processing. This is the process by which our prior knowledge affects how we perceive sensory information. It has been demonstrated that our expectations regarding a particular sensory experience influence how we interpret it. Most optical illusions take advantage of this fact.

What do you see? Prior knowledge in LTM tells your senses what "must" be there.

Similarly, LTM influences what aspects of a situation we pay attention to--allowing us to focus on relevant information and disregard what is not important. Psychologists believe that activation of interrelated schemas is part of this system, which allows our senses to function efficiently.

Since LTM storage is organized into schemas, designers should take steps to activate existing schemas before presenting new information. This can be done in a variety of ways, including graphic organizers, curiosity-arousing questions, movies and sound clips, etc.

Graphic organizers help to activate schemas in LTM.

An important factor for retention of learned information in LTM is rehearsal. However, rehearsal need not be rote--elaborating on learned information, presenting information in a variety of different ways or through a variety of media, and providing opportunities for learners to apply and practice new knowledge or skills can all be effective methods.

Jeff Easton, Graduate Student in Educational Technology