I disagree with the comparison of split-brained humans to dolphins,
but it's possible that this comparison was presented because I wasn't
clear enough in my original post. From what I understand about split-
brained humans, no one suggest that one OR the other hemisphere was
active at once; indeed, at least in Sperry's and Sperry-type tests, it's
obvious that the two hemispheres are active simultaneously. In dolphins,
the suggestion is that they use one OR the other side at any given time
(I don't know if it's known/hypothesized if the other side of the brain
is asleep or in some other state), so that a great degree of circuitry
would have to be duplicated , present in both hemispheres, and thus in
essence they would/do have two brains, of which they alternate use.
I haven't the slightest idea if motor and/or sensory wiring in dolphins
is configured such that this theory is tenable. I just heard, read, and
noted these ideas...