Bridge is a two-team, four-person card game that was once upon a time a popular social activity and that will doubtlessly stick around as long as people are still playing cards. But Buffett says it’s more than a card game, calling it “the best exercise there is for the brain.” He also says he spends about “at least four sessions a week, about two hours a session,” which might partially explain how he’s retained his mental acuity well into his ninth decade. Buffett expanded on the appeal the game holds for him to the point that he plays around eight hours of it every week: Buffett doesn’t have any problems finding bridge partners, either, since some of his fellow billionaires are also known to be fans of the game. CNBC cites his business associate Charlie Munger as one, and Buffett’s friend Bill Gates is also a known bridge player. Buffett tells a story about a trip to China taken by Gates and Buffett as well as their wives, when “we were playing bridge while everyone was looking at the scenery … We played on the bus while balancing cards on our knees.” That was back in 1995, and Buffett’s enthusiasm for bridge evidently remains unabated in the intervening 22 years.