What language do deaf people think in ?

Anyone will think in mother tongue- even deaf. However, if he is deaf since birth, will not be able to think in any language but only observe and act on instincts.

gulshan ji is saying right if a person get deaf due to an accident then he will think in his mother language but if he is deaf from childhood he will don't hace any language to think about.

deaf people also think in the language to which he belong he has also sense to think.

If deaf people know many languages he can think in any language,if he does not know other language other than his mother language he will think in it.

I think most of time they understand things according to our actions.

For thinking language is not needed.Language is for communication only.

I agree with Gulshanji,even though they are deaf they will have a keen observation power and thoughts.