[ODE] OT: virtual creatures in games

[gl]

Sorry for the (sorta) OT post, I promise it's a one off, but I know there's
a lot of people here that have worked on virtual creatures.

Without having done any work in AI (though I understand some of the
principles behind neural nets in general), I'm wondering how feasible simple
learning creatures and/or fully evolved creatures are for use in a real
game.

Using the simple creatures that learn to walk/crawl/jump as an example, how
heavy are they on system resources (both memory & CPU)?  I'm really asking
about two cases:

a) where you have evolved a creature in a seperate app to a sufficient level
of intelligence, and just want to use its brain as is in a game, without
further learning ability - how much memory would its brain take up
(roughly), and how CPU heavy would a logic tick be?

b) where you want the creature to continue learning in-game to make its
behaviour more interesting and unpredictable.  Again, what are the resource
drains?

I'm only after very rough guides - any insight would be appreciated.
--
gl