There appear to be two classes of knowledge. Pattern knowledge, such as riding a bicycle, which we tend to learn in ways similar to the current machine learning trend. In some ways, this is "deductive knowledge". On the other hand, Explicit knowledge, such a learning to reason about proofs, which we tend to learn by teaching is symbolic. In some ways, this is "inductive knowledge.
The current machine learning trend leans heavily on Pattern knowledge. I don't believe it will extend into the Explicit knowledge domain. I fear that once this distinction becomes important it will be seen as a "limit of AI", leading to yet another AI winter. I tried to bring this up in the Open AI Gym (https://gym.openai.com/) but it went nowhere.
My experience leads me to hold the very unpopular opinion that AI requires a self-modifying system. Computers differ from calculators because they can modify their own behavior. I'm of the opinion that there is an even deeper kind of self-modification that is important for general AI. The physical realization of this in animals is due to the ability to grow new brain connections based on experience. One side-effect is that two identical self-modifying systems placed in different contexts will evolve differently. (A trivial example would be the notion of a "table" which is a wood structure to one system and a spreadsheet to the other system). Since they evolve different symbolic meanings they can't "copy their knowledge" but have to transfer it by "teaching".
Self-modification allows for adaptation based on internal feedback rather than external patterns (e.g. imagination). It allows a kind of hardware implementation of "genetic algorithms" (https://en.wikipedia.org/wiki/Genetic_algorithm). It allows "Explicit knowledge" to be "compiled" into "Pattern knowledge". This effect can be seen when you learn a skill like music or knitting. After being taught a manual skill you eventually "get it into your fingers", likely by self-modification, growing neural pathways.
Of all of the approches I've seen I think Jeff Hawkins of Numenta (https://www.amazon.com/Intelligence-Understanding-Creation-I...) is on the right track. However, he needs to extend his theories to handle self-modification in order to get past the "pattern knowledge" behavior.
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