floppy tongue?

I have a friend whose son is on the autism spectrum. He is 4. He recently started doing something and we are trying to figure out why and what it could mean. He has started stcking his toungue out when he he doesn't like something or doesn't want to do it. Its not like the way children generally stick out their tongues in defiance- the stiff tongue out. He just hangs his tongue out there, floppy. WE have no idea why or where he got this from or what it could mean.