yeah nah I dunno

Yeah = yes a) I understand the question, b) it was me, c) i might agree with what you are saying. Nah = No a) I don't think thats right, b) it was not me, c) there is no useful information i can give you, d)come to think of it, maybe i don't agree with you. I dunno = I'd like to put in a disclaimer and nullify anything I just said. Non committal. Common in Australia.

It's just complete confusion and laziness rolled into one. When your really not sure if you want to do something but don't want to give a straight up answer