Train! Train!

Ari is utterly obsessed with trains.
Every time we see a train, a railway crossing, a tram, even some overhead tram wires, he will yell "train, train!" from the pram or car.
I don't know what it is about trains that he adores so much, but I think it's my first foray into the World of Boys Stuff I Don't Understand.
I was made aware of this recently at a playground when Ari and Rob spent ages playing with a digger in a sandpit. Boys just LOVE to dig holes. Rob can't seem to explain why in any way that makes sense to me - the closest he has come is to say that it's a satisfying task. Mmmm. Still don't get it.
Another example was at Coburg Lake recently when Ari picked up a stone. Rob said "watch him, he'll throw it in the river". Sure enough, he did.
The world of boys...