Bala Cynwyd’s Jeff Yass has managed to parlay his past in professional poker and horse race handicapping into a whopping $12 billion fortune with his gambling instincts, writes Antoine Gara for Forbes.

Yass is the co-founder and head of Susquehanna International Group, the global trading powerhouse. Last year, Susquehanna’s quants traded around 1.8 billion stock options contracts, which is 80 percent more than during the previous year, and accounted for close to a quarter of all options trades in the United States.

Yass started Susquehanna partly using capital he won from racetrack pots and poker tables during the 1970s and early 1980s. During the 1980s bull market, he applied his winning gambling instincts to options markets with great success.

His number one trading rule is also the main rule of every poker professional: make sure to bet against a “mark,” somebody who is dumber or less experienced than you.

“All of sports betting, all of playing poker, and all of options trading is making sure you’re betting against someone you’re smarter than,” said Yass. “If you’re not asking yourself, am I the sucker, or am I the bait, you get arrogant and you get crushed.”

Read more about Jeff Yass‘ gambling instincts in Forbes.