does tortoise brain size affect behavior?

I'm going to use Maggies "Bob" as an example here. Bob seemed to show some very interesting behavior and some reasoning skills.
Is it thought or known to be the case that larger species of tortoises with larger brains are more intelligent? Or does there seem to be some sort of a "WALL" that limits tortoise brains from further development?

Thanks

I have read a few articles about tortoise intelligence that I will try to find, but I recall that Redfoots came out best for tortoises in memory and learning, comparable to some mammals. They were said to be even able to learn and copy other tortoises, the first aping behaviour observed in reptiles.
So your lot are tortoise Smarty-pants', Ed.
Greeks weren't much cop, though.