Good question! Brain size doesn’t necessarily relate to intelligence. If you look at two people with the same brain size, they won’t be the same intelligence – it relies a lot on the environment for one thing!
In addition to that, boys and girls think in very different ways glama. Boys tend to be a lot more visual/spacial based than girls, whilst girls have a much better grip of the language part of their brain. If for example you give a boy and girl instructions of how to build a book case, the boys will tend to look at the pictures, whilst the girls will read the instructions!
Whale brains are bigger than human brains (by a long way), but they’re not smarter than us. Much of the size of the brain depends on the size of the body, and as men generally have more muscle (that needs careful control) than women, its probably for this reason that they have marginally bigger brains. The differences are very small though, and its more a question of how good the wiring is than how heavy the hardware is. So, its more to do with brawn than brain!
There is a very old pseudoscience called “phrenology” which used to look at the size of different parts of the skull and use it to infer things about peoples minds and brains – it doesn’t work.