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To me, at least, the answers to these are empirical; as @ylecun and others argue, the proof is in the pudding. We can only do so much armchair philosophizing, at some point we find out the answers by showing what works.
Absolutely, but there is empirical work by me (Cognitive Psychology 1998, further explicitated in 2001 book), recently extended by @LakeBrenden that is absolutely crucial and being largely ignored, to the peril of the field.
