Berliner started a new career in 1969, enrolling in the doctoral program at
Carnegie Mellon University to study
computer science, under the supervision of
Allen Newell. While a graduate student, Berliner was the subject of a detailed study of chess perception and short-term-memory recall in experiments inspired by the earlier work of
de Groot, and conducted by Chase and
Simon. The analysis of Berliner (compared with a Class A player and a novice) formed a basis for their contribution to the theory of
chunking in Psychology. Berliner's 1974 thesis was titled: "Chess as Problem Solving: The Development of a Tactics Analyzer". His subsequent research at Carnegie Mellon eventually led to the creation of
HiTech. At first it performed well, but only until it ran into transitions, i.e., points in the game when the balance between the players changed. This led Berliner to conclude that HiTech was weak in board evaluation. He decided that to explore the problem, he should write an evaluation function for another game:
backgammon. The result was BKG, written in the late 1970s on a DEC
PDP-10. Early versions of BKG played badly even against poor players, but Berliner noticed that its critical mistakes were always at transitions. He applied principles of
fuzzy logic to smooth out the transition between phases, and by July 1979, BKG 9.8 was strong enough to play against the ruling world champion
Luigi Villa. It won the match 7–1, becoming the first computer program to defeat a world champion in any game. Berliner states that the victory was largely a matter of luck, as the computer received more favorable dice rolls. He also developed the
B* search algorithm for game tree searching. HiTech was the first computer chess system to reach the 2400 (senior master)
USCF rating level. It won the Pennsylvania State Chess Championship several times. Students who worked with Berliner on the project included
Carl Ebeling and
Murray Campbell. Berliner was elected a Founding Fellow of the
Association for the Advancement of Artificial Intelligence in 1990. ==Writing and retirement==