Sentence:  The joint investigations of linguistics and psychiatry have <WSD>established</WSD> , in point of fact , that no matter what the subject of conversation is or what words are involved , it is impossible for people to talk at all without telling over and over again what sort of people they are and how they relate to the rest of the world . 
Meaning of the word marked with <WSD> tags:  establish the validity of something, as by an example, explanation or experiment