Do any native speakers of East Asian languages lisp? Are there any speech impediments that are unique to that language group?
I work with Japanese speakers and I have run into a few who have had lisps (even when speaking Japanese). I’m sure that there are many different kinds of problems but the one I have noticed is the “th” sound for “s”. Something like, “Sou nan desu ka” would sound like, “Tho nan dethu ka”. I find this particularly interesting because “th” is not a natural sound in Japanese and trying to teach someone to use it properly can be a real chore.