n.
born March 19, 1927, San Francisco, Calif., U.S.
died July 19, 1992, Pittsburgh, Pa.
U.S. cognitive scientist.
He taught at Carnegie Mellon University from 1961 until his death. In the late 1950s and early 1960s he collaborated with Herbert Simon in constructing an influential model of human problem solving ( Human Problem Solving , 1972). His later work was concerned with artificial intelligence, and he is known for his development of computer models of human cognition and the development of a unified theory of cognition ( Unified Theories of Cognition , 1990). In 1992 he received the National Medal of Science.