“Jeopardy!” is supposed to be a knowledge game—pop culture’s I.Q. test, it has been called—but it’s really a test of reflexes, especially when the players are first rate. Michael Dupée, a “Jeopardy!” champion and the author of “How to Get on Jeopardy!… and Win,” estimates that, nine times out of ten, all three contestants think they know the answer well enough to push their buzzers. But timing is everything. You need to push it at the moment Alex Trebek finishes the last syllable of the clue and someone else activates small white lights on the playing board. If you buzz in before the lights go on, you’re locked out for a fifth of a second. But if you hesitate, you’re beaten.

Randall Eng, who was a contestant in 2008, won $28,001 in his first game and lost the second by a dollar, after missing the Final Jeopardy question. He told me in an e-mail:

The Jeopardy people tell you to wait until you see the light to buzz in, but in practice (and I had read this online before going on) if you wait to time the buzzer off of the visual of the light, then someone else will ring in first. It’s much more practical to time it off of when you think Alex is done than to wait for the light. This might seem like it would be hard to gauge—because what you’re actually doing is not only timing when Alex is done, but also timing when the Jeopardy staff member determines Alex is done and has activated the light. So you’re essentially reacting to someone else’s reaction to someone else finishing talking, and it’s really like a fraction of a second after Alex is done that you have to ring in. But Alex’s vocal cadences are fairly consistent, so if you watch enough of the show, this seemingly complicated timing mechanism is not that hard to figure out.

Eng is describing what neuroscientists call the P300 response, and his training sounds a lot like a military experiment described by Dr. Scott Wolfe, an orthopedic surgeon:

They’ll condition a soldier to recognize a certain tone. When he hears that tone, he will have to activate a buzzer. A series of tones is played, but it’s just that one tone he has to react to. By monitoring his brain waves, they’ve actually shown that the recognition takes about 300 milliseconds.

Dr. Wolfe, who is the chief of hand and upper extremity service at the Hospital for Special Surgery, in New York, says it takes another hundred milliseconds for the soldier or Ken Jennings to press the buzzer. “A computer is basically going to beat a human every time,” he said. “In a human, the brain needs to activate a whole series of synapses to make our muscles move and our hand then press the buzzer. It’s not just a single reflex.”

So your ears hear Trebek finishing his last words, your eyes see the white light come on, then they send a signal to your brain which sends out another signal down the spinal column to your thumb telling it to press the buzzer. Meanwhile, Watson can’t hear, so it’s not listening for Trebek to finish his sentence, and it can’t see, so it isn’t watching for the lights. When the lights go on Watson receives an electronic signal. As Ezra Deutsch-Feldman reported on the New Republic Web site, an early version of Watson did its buzzing by sending an electronic signal back, but that was too much of an advantage. So I.B.M. engineers built a mechanical hand and a buzzer for Watson to press.

Time and again, we have seen the humans mashing their thumbs down on the buzzer (especially Ken), only to give a frustrated shake of their heads, as Trebek calls on Watson again and again. Jennings and Brad Rutter might have been much closer if I.B.M. had compensated properly for the P300 response. This doesn’t take away from I.B.M.’s core achievement—which is building a machine capable of answering a wide range of pretty hard questions. But it does take away from Watson’s success in the game. A quick trigger isn’t particularly useful, unless you’re a soldier, nor is it particularly “intelligent,” or, in this case, fair.

Tonight’s final showdown was more competitive: the first round was the closest of the three nights. But in the Double Jeopardy round, Watson put the hammer down, getting both Daily Doubles, and finishing with a five answer streak. Game Over.

I watched the contest with a number of I.B.M. people, including the leader of the Watson project, David Ferrucci, in Spin, a ping-pong parlor on Twenty-third Street. I asked Ferrucci about the discrepancy in buzzer skill, and wondered whether this devalued Watson’s victory. Ferrucci, who talks more like a car mechanic than a computer scientist (which is part of his charm), acknowledged that Watson was “the dominant buzzer. I’m not saying he’s not. But hey—that’s the game. Ken Jennings. How’d he win so many games against humans? The buzzer! In some of his games, he got the buzzer eighty per cent of the time. Tonight he just ran into a better buzzer.” Ferrucci added, “But this is not about winning the game. I.B.M. is not going to develop a revenue stream based on winning “Jeopardy!” games.” But winning this “Jeopardy!” game could get other streams flowing.

Or Watson could learn poker.