Wednesday, July 28, 2010

Memory Organization.

Memory Organization:

Memory is the central to commonsense behavior. Human memory contains an immense amount of knowledge about the world. Memory is also basis for learning. A system that cannot learn cannot in practice, possess common sense. A complete theory of Human memory has not yet been discovered, but we do have a number of facts at our disposal. Some of these facts come from neurobiology, while others are psychological in nature. Computer models of neural memory are interesting, but they do not serve as theories but how memory is used in every day common sense reasoning. Psychologically AI seeks to address these issues.

Psychological studies suggest several distinctions in Human memory. One distinction is between Short Term Memory (STM) and Long Term Memory (LTM).

LTM is often divided into episodic memory and semantic memory. Episodic memory contains information about past, personal experiences. Semantic memory on the other hand contains facts like “Bird Fly”. These facts are no longer connected with personal experiences.

Models for episodic memory grew out of research on scripts. Recall that a script is a stereotyped sequence of events such as those involved in going to the dentist. In general it is difficult to know which script to retrieve one reason for this is that scripts are too monolithic. It is hard to do any kind of partial matching. It is also hard to modify a script. More recent work reduces scripts into individual scenes.

Usually three distinct memory organizations packets (MOPS) e code knowledge about an even sequence.

One MOP represents the Physical sequence of events.

Another MOP represents the set of social events that takes place.

Third MOP revolves around the goals of the person in the particular episode.

MOP’s organize scenes, and they themselves are further organized into higher level MOP’s. For example, the MOP for visiting the office of a professional may contain a sequence of obstruct general scenes, such as talking to an assistant, waiting and meeting. High level MOP’s contain no actual memories. New MOP’s are created upon the failure of expectations. With MOP’s memory is both a constructive and reconstructive process. It is constructive because new experiences create new memory structures. It is reconstructive because even if the details of a particular episode are lost, the MOP provides information about what was likely to have happened. The ability to do this kind of reconstruction is an important facture of Human Memory.

There are several MoP based computer programs. CYRUS program that contains episodes taken from the life of a particular individual. CYRUS can answer questions that require significant amounts of memory reconstruction. The I I P program accepts stories about terrorist attacks and stores them in an episodic memory. These structures improve the ability of understand.