My son chews his tongue - Help

[Cluffy74 10]

My son chews his tongue when he is concentrating and when he is tired. The thing drives our family mad as he makes a really loud noise and has no idea he is doing it. It sounds like he is chewing a huge piece of plastic.

 

Anyone any experience with this kind of thing and any ideas on how to help him to stop.

 

I know it doesn't sound like much but it is a real pain.

 

Ta x