Tired Tonight

Really tired tonight after a work day, then a delightful evening of playing dog and train conductor. Planning a lovely sleep with a little guy and a Sponge Bob night light that shines on the ceiling. And wondering, what is it about this little boy and his mechanical abiity. I can do something and he focuses, then he's got it. Is this just what little boys do? Is there really a difference between boys and girls? At age four?