Notably, the characterization of intelligence as a spectrum grants no special status to the human brain. But to date human intelligence has no match in the biological and artificial worlds for sheer versatility, with the abilities “to reason, achieve goals, understand and generate language, perceive and respond to sensory inputs, prove mathematical theorems, play challenging games, synthesize and summarize information, create art and music, and even write histories.”
This makes human intelligence a natural choice for benchmarking the progress of AI. It may even be proposed, as a rule of thumb, that any activity computers are able to perform and people once performed should be counted as an instance of intelligence. But matching any human ability is only a sufficient condition, not a necessary one. There are already many systems that exceed human intelligence, at least in speed, such as scheduling the daily arrivals and departures of thousands of flights in an airport.
AI's long quest—and eventual success—to beat human players at the game of chess offered a high-profile instance for comparing human to machine intelligence. Chess has fascinated people for centuries. When the possibility of building computers became imminent, Alan Turing, who many consider the father of computer science, “mentioned the idea of computers showing intelligence with chess as a paradigm.” Without access to powerful computers, “Turing played a game in which he simulated the computer, taking about half an hour per move.”
But it was only after a long line of improvements in the sixties and seventies—contributed by groups at Carnegie Mellon, Stanford, MIT, The Institute for Theoretical and Experimental Physics at Moscow, and Northwestern University—that chess-playing programs started gaining proficiency. The final push came through a long-running project at IBM, which culminated with the Deep Blue program beating Garry Kasparov, then the world chess champion, by a score of 3.5-2.5 in 1997. Curiously, no sooner had AI caught up with its elusive target than Deep Blue was portrayed as a collection of “brute force methods” that wasn't “real intelligence.” In fact, IBM's subsequent publication about Deep Blue, which gives extensive details about its search and evaluation procedures, doesn’t mention the word “intelligent” even once! Was Deep Blue intelligent or not? Once again, the frontier had moved.
 Nilsson, The Question for Artificial Intelligence.
 Nilsson, The Question for Artificial Intelligence, 89.
 McCorduck, Machines Who Think, 433.
 Murray Campbell, A. Joseph Hoane Jr., and Feng-hsiung Hsu, “Deep Blue,” Artificial Intelligence 134, nos. 1 and 2 (2002): 57—83.