Obsessed with letters and numbers

No matter where we are, Ian will stop and point to each letter on an object. I can't wear a t-shirt with lettering or he'll be pointing to me all day. Every time we get home, I out him down to walk into the house and he stops at the front license plate to point at each number and letter until I say it and sign it. It's amazing to watch. In this pic he's found the logo on our neighbor's truck.