[Hodar]

Some dolphins brains are bigger than yours and mine.

That is correct, but ours have far more convolutions (folds), thus the surface area of our brains is larger. That's one of the reasons we are smarter than dolphins, and also why we are smarter than apes. Our brains are far more evolved or advanced.

[jwalsh07]

The Capuchin monkey, which many experimental psychologists regard as equal in docility (i.e., educability) to any highly gifted chimpanzee, possesses an almost smooth brain surface, whereas the chimpanzee has a wrinkled one that comes close to that of man.