My son is 14 months old and still not crawling (nor walking). He sits, rolls and can propel himself a couple of metres using his arms (not sure if this is what's meant by 'commando style') if he really wants to, but seems to have no inclination to do anything more. If I put him in the middle of the room in a sitting position, not near any toys, he will just stay like that. He is generally fairly laidback and happy so I can't decide if he's lazy, not bothered, or if there might actually be something wrong. Any tips on how to make him move more?