Fierce competitors: born or made? There's plenty of evidence to suggest that some individuals are just hard-wired that way.
People with higher levels of testosterone (associated with dominance) and low levels of cortisol (stress) typically participate in riskier behaviors and remain "calm, cool and collected" under pressure, says Pranjal Mehta, head of the University of Oregon's Social Psychoneuroendocrinology Lab.
Competition, adds Kacey Ballard, a neuroscientist at San Francisco-based "brain training" software company Lumosity, evokes biological responses that stir up feelings of envy, empathy and schadenfreude (as well as, it seems, the desire to build companies). "My co-founder and I bonded in college competing in foosball and ping pong," says Lumosity's chief scientist and CEO Mike Scanlon. "It's how we discovered a common goal and definition of success: winning."
To find out what else sets a great competitor apart, we chose Mark Zuckerberg as our lab rat. Because you don't become the world's youngest billionaire by believing that "everyone's a winner" crap.