Most of us believe that a coin flip can resolve nearly any stalemate fast and fairly. The ancient Romans called this navia aut caput, referring to the ship and the head on the two sides of their coins. Flipping a coin seems like a reasonable way to resolve such standoffs because it appears just as likely to land on heads or tails. Except that it isn’t. A few years ago, a group of medical residents were each asked to flip a coin 300 times under rigorous testing conditions and to try to make the coin come up heads on each flip. These were not gamblers or con artists, and they were not given much time to practice. Nevertheless, each resident was able to flip more heads than tails. One resident turned more than 200 heads, for a hit rate of 68 percent—far above random chance. Statisticians from Stanford University analyzed the physics of coin tossing and determined that without any mischievous intent on the part of the flipper, a fair coin will tend to land facing the same way it started. The same-side advantage is small (51 to 49 percent); but if true, who would ever agree to a coin toss again?