The brains of Ken Jennings, James Holzhauer, and Lancaster County native Brad Rutter are crammed with facts, as evidenced by the trio’s success as the top money-winners on Jeopardy!

But as the three compete in the game show’s “Greatest of All Time” tournament airing this week, Holzhauer has an attribute that no amount of cramming can change: youth.

At 35, he is six years younger than Rutter and a decade younger than Jennings, potentially enough of a difference to give him a small, but significant, advantage in reaction time.

Studies suggest that “simple” reaction time — say, the amount of time it takes a person to push a button after seeing a light go on — remains fairly constant until age 50. But “choice” reaction time, in which a person has to choose among several alternatives before responding to a stimulus, starts to deteriorate as early as the mid-20s, said Joseph Thompson, a cognitive scientist at Douglas College in British Columbia.

On average, the choice reaction time of a 35-year-old is one- or two-hundredths of a second faster than that of someone just five years older, studies have found. A 45-year-old is another hundredth of a second or two slower than that, and the rate of decline becomes steeper with age.

A few hundredths of a second is less than the blink of an eye, literally.

“It’s nowhere near as strong an effect as just being better at the game,” Thompson said.

But these three contestants all are extremely good at Jeopardy! So even the slightest edge in reaction time could be enough to make a difference, as the first person to hit the buzzer gets first crack at responding to a clue.

In an interview with the TV show Seattle Refined, Jennings said he feels the effects of his advancing years.

“I can tell you firsthand that age matters on Jeopardy!” he said. “I wish it didn’t, because I am 15 years older than when I first played, but I can tell the difference. I’m a little bit slower on coming up with names, and my rhythm isn’t that great on the buzzer.”

The biology behind why reaction time worsens with age is not fully understood, said Thompson, who teaches in the psychology department at Douglas.

The answer depends in part on what phase of the neurological chain of events is being measured. There is the amount of time it takes for a signal, such as the voice of Jeopardy! host Alex Trebek, to travel from the ear to the brain. Then there is the amount of time it takes for that signal to be processed and acted upon. And there can be overlap between these different phases of the process. Evidence suggests that the brain can carry out some of these tasks in parallel, Thompson said.

As a graduate student at Simon Fraser University, he and supervisor Mark Blair studied the effects of age on performance in players of a video game called StarCraft II.

Technically, they did not measure reaction time but a related measure called “looking-doing latency” — the speed at which a person initiates an action in response to his or her own decisions.

The resulting study, published in 2014 in the journal PLOS ONE, had a downer of a title: “Over the Hill at 24.”

All is not lost for the seasoned competitor, however. Thompson said people with years of experience in a given game or task can compensate by anticipating what is about to happen, such as a veteran baseball slugger who can predict where a pitch will be thrown.

And on Jeopardy!, an experienced contestant need not wait for Trebek to finish reading a clue in order to get the gist of it. The clues are displayed on the board, as well, so Jennings can read them and get ready to hit the buzzer the moment Trebek stops speaking.

Then again, so can Rutter and Holzhauer.

The first match in the championship series will air Tuesday at 8 p.m. on ABC, with more to follow, as needed. The first contestant to win three matches will receive $1 million, while the two others get $250,000 — a hefty payout even for those who are a split-second slower at the buzzer.