Recently I wondered with DS11 if all little boys could be divided into ones who love Dinos v. one who love trains or trucks...
Funny you should say this...I swear by this observation!
I have yet to meet a boy who loves both wheeled vehicles AND dinosaurs. They might like one okay and love the other, but there always seems to be a marked preference for one and only one.
I have wondered if it's somehow related to engineering vs. humanities or math vs. science, but I have yet to make that leap stick, even for my own uncritical generalization.