Among his major contributions to linguistic theory was the hypothesis that certain languages were
non-configurational, lacking the phrase structure characteristic of such languages as English. Non-configurational languages, according to Hale, display a set of properties that cluster together, including free
word order, unpronounced pronouns and the ability to disperse semantically related words across a sentence. Much of his research in the last two decades of the twentieth century was devoted to the development of syntactic models that could explain why these properties cluster. Hale's ideas initiated an important research program, still pursued by many contemporary linguists. In 1960, Hale's recording of a short text from one of the few remaining native speakers of the
Diyari language (spoken in northern South Australia) was the first research by a professional linguist into that language. Hale took care to educate native speakers in linguistics so they could participate in the study of their languages. Among his students are the Tohono O'odham linguist
Ofelia Zepeda, the
Hopi linguist
LaVerne Masayesva Jeanne,
Navajo linguists
Paul Platero,
MaryAnn Willie, and
Ellavina Tsosie Perkins, and
Wampanoag linguist
Jessie Little Doe Baird. Hale taught every summer in the
Navajo Language Academy summer school, even in 2001 during his final illness. In 1990 he was elected to the
National Academy of Sciences. Hale championed the importance of under-studied minority languages in linguistic study, stating that a variety of linguistic phenomena would never have been discovered if only the major world languages had been studied. He argued that any language, whether it has a hundred million native speakers or only ten, is equally likely to yield linguistic insight. Hale was also known as a champion of the speakers of minority languages, and not just of their languages, for which his MIT colleague
Noam Chomsky called him "a voice for the voiceless". ==Linguistic Society of America==