More than coincidence? Identical twins Ronde and Tiki Barber, shown here at the 2006 NFL Pro Bowl, each had a storied and successful football career—Ronde with the Tampa Bay Buccaneers and Tiki with the New York Giants. Studies of twins suggest that some aspects of behavior and personality are influenced by genetic factors. Many identical twins, like the Barbers, have similar tastes, behave in similar ways, and make similar life choices. Some even develop similar abnormal behaviors.