The psychology of a language which, in one way or another, is imposed upon one because of factors beyond one's control, is very different from the psychology of a language which one accepts of one's free will.

Ishi died of his illness in early 1916 and Kroeber partly blamed the exacting nature of working with Sapir for his failure to recover. In the end Sapir didn't finish the work during the allotted year and Kroeber was unable to offer him a longer appointment. His students included Fang-kuei Li Benjamin Whorf Mary Haas and Harry Hoijer.

While finishing his PhD he went to California to work with Alfred Kroeber documenting the indigenous languages there. Before Sapir it was generally considered impossible to apply the methods of historical linguistics to languages of indigenous peoples because they were believed to be more primitive than the Indo-European languages. Later in his career he also worked with Yiddish Hebrew and Chinese as well as Germanic languages and he was also invested in the development of an International Auxiliary Language.