How Much of the Brain is Understood?

A few days ago, right after talking to Steve Wozniak, my friend Ken Kopecky and I were talking about how much of the brain is understood. He asked me roughly how much of it I thought I understood (which is sort of an ill-posed question, but anyway...), and I said maybe 50%. He replied, "That's a very bold statement, Tyler Streeter." I said, "Ya, I know."

The next day I thought more about that conversation. I realized that I should have qualified my response a bit. I talked to Ken again, saying that I was mainly referring to the brain's functional/computational aspects. I said, "My 50% estimation from the other day was not meant to imply that I am especially intelligent, but that the functional, computational aspects of the brain are not as complex as most people think."

To elaborate a bit, some of the key elements (also described in my notes posted earlier) are probably:
* Data compression/feature extraction (e.g., principal components analysis, clustering)
* Reinforcement learning (e.g., temporal difference learning)
* Planning/imagining (e.g., using a learned predictive model of the world to enable reinforcement learning from simulated experiences)
* Curiosity rewards (e.g., intrinsic rewards from novel, learnable information)
* Temporal processing/short-term memory (e.g., tapped delay lines)