The difference between girls and boys.

Noah: “Mummy, Thomas runs on coal. He loads and shunts”.

Ivy: “Yes, and he has a shiny blue colour on his engine and some pretty red bits too”.

Noah (sneering in his sister’s general direction): “No, Ivy, that’s not the exciting part. Thomas, he runs on coal!”

It seems gender biased vehicle selection criteria starts early when you have boy – girl twins in the house.