I think they suffer from the problem that the brain is very complex, and it's impossible to boil it down to simple - and testable - rules. Rule-based, understa

I think they suffer from the problem that the brain is very complex, and it's impossible to boil it down to simple - and testable - rules. Rule-based, understandable, AI has mostly been replaced by deep learning, which is more difficult to understand. It has useful properties, but we don't know why, they're emergent.