ds is just 9 months. he can sit up quite well but still likes to lie down a lot. when he sits up in a chair or whenever he's upright he has a habit of flipping his head backwards (or tilting it sideways) to view the world upside down. he's always doing it - when he watches tv, when he's looking at other people or something that interests him - it's quite funny and i just wonder why? i'm not worried, just curious?