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General Intelligence :

Memory systems

1. Semantic Memory
2. Generic Memory
3. Episodic Memory
• memory consolidation
4. Procedural Memory
5. Working Memory

Memory management: forgetting and saliency

Semantic memory (S_M)

Semantic memory stores the meaning of concepts. The concepts are themselves nameless, but they may be given names by the natural language processor.

Some examples of semantic memory items:

1. the meaning of "fighting"
2. the meaning of "beautiful"
3. the meaning of "justice"

S_M contains rules for the Pattern Recognizer.

Generic memory (G_M)

In cognitive psychology, generic memory includes all declarative memories that are not episodic (ie happening at a particular time) in nature, so it includes semantic memory as well. We take the liberation of using G_M to mean generic memory excluding semantic memory.

Examples of generic memory items:

1. Entropy always increases.
2. People go to a bar typically to have fun.
3. Oil is slippery.
4. Boltzmann committed suicide in 1906.

G_M is used heavily by the Inference Engine to make inferences from knowledge. It is not just a passive storage device. Recall of facts can be triggered automatically by the presence of facts in Working Memory, or by explicit request from the Inference Engine, Planner, etc.

GM should be organized by categories to facilitate efficient recall, eg historical facts, scientific facts, facts about people, etc.

Episodic memory (E_M)

Episodic memory stores events, ie, facts occurring at specific times, and are compressed from sensory experience. Therefore, "Boltzmann died in 1906" should be in Generic Memory, not in Episodic Memory.

Examples of episodic memory items:

1. I met Kellie at a party last week
2. White played d2-d4 (during a game)
3. Bush was re-elected president in 2004 (may be transferred to Generic Memory)
4. I learned the second law of thermodynamics from a physics textbook 20 years ago.

An important function of learning is to generalize facts from Episodic Memory and place the conclusions in Generic Memory. Generic Memory should contain links back to the facts supporting those conclusions.

Memory consolidation

The main mechanism of consolidation is the forgetting of unimportant (low-saliency) details. For example, sensory memory may contain minute visual details such as "flowers patterns on grandma's dress". Primary memory may contain the fact that "grandma was in the shopping mall", without details of her dress. Further consolidation at higher stages may be like "grandma often brought me to the mall when I was a kid".

{ To do: There may be a memory consolidation cycle during "sleep". The whole system, including the Inference Engine and Pattern Recognizer, may be freed to involve in this process. }

A hierarchical organization of episodic memory may be needed (eg sensory-, primary-, and secondary- memory). It depends on further experiments to see if it is necessary.

Procedural memory (P_M)

A memory system used by the Planner exclusively.

Working memory (W_M)

Working Memory functions as a workspace or "blackboard". W_M is passive; it provides a common workspace and does not control how its contents are used.

Humans working memory seems to be able to hold about "7 ± 2" chunks.

A module can issue requests to other modules via W_M. For example, the Planner may issue a request for Generic Memory to search for all rules with the head Says(person,something).

Forgetting and saliency

Contents in the memories can be labeled with saliencies (or "degrees of importance "). Low saliency nodes will be forgotten (ie, discarded as garbage) periodically.

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