Noam Chomsky is an American linguist, philosopher, political activist, author, and lecturer. He is an institute professor emeritus and professor emeritus of linguistics at the Massachusetts Institute of Technology. Chomsky is well-known in the academic and scientific communities as the father of modern linguistics. Chomsky received his PhD in linguistics from the University of Pennsylvania in 1955. In 1961, he was appointed full professor in the Department of Modern Languages and Linguistics at M.I.T. According to the Arts and Humanities Citation Index in 1992, Chomsky was cited as a source more often than any other living scholar was during the 1980–92 period.