Warren Buffett spends 8 hours a week playing the 'only game' at which he may be better than Bill Gates

Warren Buffett, chairman of Berkshire Hathaway Inc., right, and Bill Gates, chairman and co-founder of Microsoft Corp., participate in a newspaper toss event at the Berkshire Hathaway annual shareholders meeting on Saturday, May 5, 2012.
Daniel Acker | Getty Images

Berkshire Hathaway chairman Warren Buffett is known for spending as much as 80 percent of his day reading. But when he's not learning or working, chances are the billionaire is playing bridge. 

"I play a lot," Buffett told Thomas Heath of the Washington Post in a 2017 interview. "At least four sessions a week, about two hours a session." That's a minimum of eight hours a week.

Over time, he's honed the skill to the point where he can typically beat his good friend Bill Gates, who's also a fan of the card game. "I probably play 100 times as often as Bill, so that probably is the only game in the world where I would have a slight edge with him," Buffett told CNBC's Becky Quick in an exclusive interview on "Squawk Box" on Monday.

"Very slight edge," he added.

Warren Buffett, chairman of Berkshire Hathaway
Daniel Acker | Bloomberg | Getty Images

Buffett, who is, at 88 years old, as sharp as ever, likes how bridge keeps him on his toes.

"You can play a hand every six or seven minutes every day for the rest of your life, and you will never see the same hand," he told Heath. "It's a game you can enjoy when you are in your 90s, and you are seeing a different intellectual challenge every seven minutes."

It's not too surprising that billionaires Buffett and Gates make time for a game that gets them thinking. Author Steve Siebold, who has studied more than 1,000 wealthy people, found that they would generally rather be educated than entertained. "The rich like entertainment but love to learn, and they spend their entire lives soaking up information and using it to get richer every day," he writes in his book, "How Rich People Think."

The card game may also keep the billionaires sharp for longer: Those who engage in mentally stimulating activities experience slower memory decline than those who do not, research published in the Journal of American Academy of Neurology finds.

And bridge may be the most mentally stimulating activity out there, according to Buffett: "It's the best exercise there is for the brain," he told Heath.

Don't miss: 11 of Warren Buffett's funniest and most frugal quirks

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Warren Buffett's most eccentric traits
Warren Buffett's most eccentric traits