User blog comment:CNBA3/Chapter 405 Review/@comment-4829046-20141020120040/@comment-7418318-20141021124758

But one thing both Goku, Gohan and Natsu have in common, which might explain why their brains work different: None of them is entirely Human.

Goku is a full alien, Gohan is half alien and half whatever his mother's side is (they don't seem entirely Human either) and Natsu has been infused with quite a bit of Dragon. For all we know their entire thinking process could work differently.